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Supporting => Additive Machining => Topic started by: sorveltaja on April 10, 2019, 11:57:26 PM

Title: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 10, 2019, 11:57:26 PM
As a young lad, in the early 80's, I borrowed a book from the library, that had drawings of all kinds of strange mechanical devices. I can't remember, what book it was, or who wrote it.

But anyways, one specific drawing got me hooked. It presented a simplified version of an automatic transmission. It had those ring, planet, and sun gears.

Gears were changed by applying brakes on ring gears in certain order. I couldn't fully understand it, but regardless of that, I was still baffled and excited about it.

Of course, there was no way of producing any of that to physical form back then.

More than few years ago, I made an attempt to machine the ring gears, abusing my PF 230 mill, as a broaching device:
(http://www.elisanet.fi/kz1706/broaching_tool.JPG)

Very laborious way, and also very tedious to say at least.

But let's get back to the present day. When I got the 3d-printer, I started to search drawings for similar, simplified version of an automatic transmission on the net.

The best I could find was this:
(http://www.elisanet.fi/kz1706/gearbox.jpg)

Source is at http://project38.net/category/paperwork/.

On that site, there is also a very hugely sized cad drawing of that transmission, but I haven't been able to find any of the actual linkages between the gears of that drawing.

No problemo. I made my own interpretation of the original drawing:
(http://www.elisanet.fi/kz1706/3d_work.jpg)

Here comes the first attempt:
(http://www.elisanet.fi/kz1706/printed_gears_for_testing.JPG)







Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: crueby on April 11, 2019, 12:13:18 AM
Wow - that is quite a mechanism! Something that I also remember seeing drawings of, but never really following well. Like you say, nothing like having one in hand to spin and study. I'll be very interested in how this progresses!
 :popcorn: :popcorn: :popcorn:
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Johnmcc69 on April 11, 2019, 12:43:07 AM
A very cool & ambitious project. Trying to figure out gear trains makes my head spin. :insane:

 Looking forward to your progress with this. You're off to a great start & doing some really nice work.

 John
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: AdeV on April 11, 2019, 08:23:53 PM
This page (https://www.roadrunnerconverters.com/blog/how-automatic-transmissions-work-with-pictures-videos.htm) (and the embedded video in particular) might help clear up how it works. The only thing that's not obvious is which shaft is rotating at the input end, watching it a few times should make it fairly obvious.

Making the clutches/brakes work properly would, I'd have thought, be the hardest bit, if using a 3D printer...
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: crueby on April 11, 2019, 09:24:07 PM
This page (https://www.roadrunnerconverters.com/blog/how-automatic-transmissions-work-with-pictures-videos.htm) (and the embedded video in particular) might help clear up how it works. The only thing that's not obvious is which shaft is rotating at the input end, watching it a few times should make it fairly obvious.

Making the clutches/brakes work properly would, I'd have thought, be the hardest bit, if using a 3D printer...
Great video, explained a lot - thanks for that!
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: cnr6400 on April 12, 2019, 12:08:24 AM
I thought Ezekiel invented the planetary transmission, with the wheels within wheels    :thinking: .... but maybe he just saw the video too..... :Lol:

or worked for Bunkie Knudsen and Henry Ford Sr. on the 1915-1923 Model T. It had a planetary box with three brake bands. 2 speeds forward (slow and too fast) 1 reverse, brakes rear wheels only, with skinny tires, wise people carried an anchor to toss out if in hilly country.  :facepalm:
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 12, 2019, 12:16:59 AM
AdeV, thanks for the link. That Ravigneaux gear set is definitely much more compact, than the one I'm working on.

Found this one: https://www.selmec.org.uk/article_0001_ravigneaux_planetary_transmission.aspx
Fig.3 shows the number of teeth of the gears, and that's pretty much all, that I need to draw a 3d-model of it.

And yes, the PLA plastic, that I use for printing, isn't really the best candidate for parts, that face friction between one another. It tends to get warm, and therefore galls fairly easily.
Somewhere I read, that boiling the printed parts in hot water might 'anneal' them to some extent. It would also shrink the objects, so not sure about that.

John isn't the only one, who's head is spinning, while trying to figure out the gear trains, They must be from some other dimension (http://emoticons4u.com/crazy/134.gif)

Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: b.lindsey on April 12, 2019, 12:56:57 AM
Great video Ade. Here is another very oldie but goodie simple explanation of how differentials work. This one even a dummy like me can understand.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://m.youtube.com/watch%3Fv%3DyYAw79386WI&ved=2ahUKEwiws4n2nMnhAhVKA6wKHfmBCxMQwqsBMAF6BAgHEAo&usg=AOvVaw2Z3IqET92ASX4b_QBTBtLj
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: crueby on April 12, 2019, 02:22:06 AM
...

Found this one: https://www.selmec.org.uk/article_0001_ravigneaux_planetary_transmission.aspx (https://www.selmec.org.uk/article_0001_ravigneaux_planetary_transmission.aspx)
Fig.3 shows the number of teeth of the gears, and that's pretty much all, that I need to draw a 3d-model of it.

...
Oh. My. That is some SERIOUS Meccano work!
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: steam guy willy on April 12, 2019, 02:53:36 AM
Hi All ..Didn't Isigonis figure out the Mini gearbox with Meccano ??

Willy
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: ddmckee54 on April 12, 2019, 06:59:43 PM
I've seen a couple of videos on YouTube, actually Army training films, that you might want to check out.  The M47 Patton tank used a planetary gearbox and one of the videos is specifically about it.  The other is just a general explanation, probably for the mechanics of the day?  When I did a YouTube search for M47 planetary gearbox, those were the first two items listed.

Don
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 12, 2019, 10:49:57 PM
Don, and all, on those old films, they really get to the point without any fuss :praise2:

I watched the M47 video, and there was so much good information, that at least for me, it takes some time to digest it.

What comes to the current gear set that I'm working on, I'm not sure yet, which sun gear is attached to the center axle, and therefore delivering torque from the motor to the rest of the gear sets. 

What I suspect, is the 'K' one:
(http://www.elisanet.fi/kz1706/suspected_drive_gear.png)

I'll have to modify the drawings to make room for the'K' to have the grub screw. Not a big deal, as at the beginning, I just wanted to get the gear sets printed out, and while assembling, make changes as is necessary.

Some of the gear sets were way too tight to fit together, so I printed consisting planet gears with 0,1mm offset, to make them rotate more freely. 


Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: MJM460 on April 12, 2019, 11:19:56 PM
Hi Sorveltaja, I am on dangerous ground here.  As you know, unlike most mechanical engineers, I used thermodynamics all my life but left gears in the lecture theatre, oh so many years ago.

But I am guessing it is A.  My reasoning is like this.

Gear ratios are changed by applying brake bands to the ring gears, or the one plain one.  K is attached to the plain one so is sometimes stationary, while the engine keeps running.  So A or F.  If I am seeing the letters correctly, F rotates the opposite way to the engine, so it must be A.  And of course we can see that the final output is through the Gang I set which is off the right hand side of the drawing.

Fingers crossed,

MJM460

Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Vixen on April 13, 2019, 12:20:28 AM
Don, and all, on those old films, they really get to the point without any fuss :praise2:

I watched the M47 video, and there was so much good information, that at least for me, it takes some time to digest it.

What comes to the current gear set that I'm working on, I'm not sure yet, which sun gear is attached to the center axle, and therefore delivering torque from the motor to the rest of the gear sets. 

What I suspect, is the 'K' one:
(http://www.elisanet.fi/kz1706/suspected_drive_gear.png)


I'll have to modify the drawings to make room for the'K' to have the grub screw. Not a big deal, as at the beginning, I just wanted to get the gear sets printed out, and while assembling, make changes as is necessary.

Some of the gear sets were way too tight to fit together, so I printed consisting planet gears with 0,1mm offset, to make them rotate more freely.

Hello Sorveltaja,

I believe what what you have illustrated is also known as the Merritt-Wilson gearset. It was used on numerous British and American tank and armoured vehicle transmissions. It was also used in the Wilson preselector gearbox (motor racing) and other makes of upmarket motor vehicle, like Damler etc. The particular advantage of the Merritt-Wilson gearset was the fact that the various gear ratios were selected by applying band brakes to the various epicyclic stages. A band brake is so much easier to make and maintain than a multi-plate clutch.


This illustration of the Daimler version, shows the flow of torque through the gearbox as each band brake is applied to select the different gear ratios. I found it useful to print a copy and colour in the torque flow path for each of the gear ratios. Hopefully this diagram will help you understand the operation of your illustrated gearbox.

(http://lister-engine.com/coppermine/albums/userpics/10013/wilson1.jpg)


I have experimented with and designed Merritt- Wilson transmissions for one of my 1/6 scale model tanks. My design was based ion the epicyclic gear clusters extracted from 3 speed Sturmey- Archer bicycle gear hubs. Still easily available, tough, robust and virtually indestructible. If I knew how, I could post a DXF file of my 4 speed and reverse Merritt-Wilson transmission.

Here are some photos of a simple mock-up of a 3 speed Merritt-Wilson transmission, quickly assembled from Sturmey-Archer components to demonstrate the basic principles. The direct dive 4th gear and the reversing stages are not present

(http://lister-engine.com/coppermine/albums/userpics/10013/DSCF4982.JPG)

(http://lister-engine.com/coppermine/albums/userpics/10013/DSCF4983.JPG)

If you are interested and provided someone can tell me how to, I could post the DXF files of my 4 speed and reverse Merritt-Wilson transmission.

Mike




Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Hugh Currin on April 13, 2019, 01:40:37 AM
For me the complex part is figuring out the gear ratios on a single epicyclic (planetary) gear train. For me, if I can figure out one it's fairly easy to treat them as a unit and stack them together. Also, braking each part of the system or freezing various parts together become feasible to calculate. But tricky to figure out one epicyclic gear train.

I found this in a machine design book years ago and have used it to calculate epicyclic gears since. Don't have the book here so I hope I can reproduce it correctly. I'm sure many of you have seen this so if I've gone wrong please let me know so I can correct.

A simple single stare planetary system, with terminology, is like this:

(http://lister-engine.com/coppermine/albums/userpics/10011/planet-1.jpg)

For this analysis assume the sun gear is fixed to the ground. Also, that the carrier rotates (if it doesn't its a simple gear train and not too hard to figure out).

The scheme is to analyze the system in two steps. First FIX the carrier arm, it rotates zero rotations. Then un-fix the sun gear and rotate it one revolution (+1). This is now a simple gear train with the carrier fixed, so determine the rotation of the other gears (planet and ring). For this example the sun gear rotates +1, the planet rotates -2, and the ring gear rotates -1/2.

(http://lister-engine.com/coppermine/albums/userpics/10011/planet-2.jpg)

The second step is to freeze all the gears and carrier together, all rusted up. Then rotate each element though -1 revolution. So the sun goes -1, carrier -1, planet -1 and ring -1.

(http://lister-engine.com/coppermine/albums/userpics/10011/planet-3.jpg)

The final step is to add up the rotation for each element found in steps one and two.

(http://lister-engine.com/coppermine/albums/userpics/10011/planet-4.jpg)

The sum has the sun gear with zero rotation, which it must have as, in reality, it's frozen to the ground. The other sums give the correct epicyclic rotations. If the carrier is rotated backwards one revolution (-1) then the planet with rotate -3 revolutions and the ring gear will rotate backwards 1.5 revolution (-1.5). One rotation of the carrier thus produces 1.5 revolutions of the ring gear. Bob's your Uncle.

I hope this is of use to someone.

Thanks.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 15, 2019, 10:44:29 PM
MJM460, I think you are right!

I Drilled right through the gear A to make the M3 thread for the grub screw, which goes through the brass tube input axle:
(http://www.elisanet.fi/kz1706/suspect_A.JPG)

Here is the first version assembled. I was able to distinguish three or four gear ratios, while operating it manually. It is rather noisy and is stiff to rotate, and has numerous not so well thought quick-fixes:
(http://www.elisanet.fi/kz1706/assembled.JPG)

While spinning it slowly with a power drill device, braking gears one by one, there was an anomalous 'unwinding' -thing happening, which locked almost the whole thing to solid lump.
So I spinned it backwards, and that locking situation was gone. I did it few times, and always the same results. 

Once again, I dismantled it, and couldn't find reason for that. All the possible suspects, like planet gears, that were fastened with screws, had also brass sleeves,
long enough to allow the gears to rotate freely, even when the screws were tightened.

Next suspect was the carrier D on the output side:
(http://www.elisanet.fi/kz1706/output_side.png)
And the actual carrier, that was still tightly fastened:
(http://www.elisanet.fi/kz1706/carrier_D.jpg)

But enough of that buggy first version.
---------------------------------------

Mike, thanks for the pictures, and yes, it would be greatly appreciated, if you could provide the DXF-files of that transmission. I'd like to make a 3d-model of it, and print the parts, to test it.
I have no idea though, of how the DXF-files could be transferred through this forum. Anyone?

Hugh, I also have troubles calculating planetary gear ratios, as there isn't that many sources, that explain it as clearly as you have done. Big thanks for that.



Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Vixen on April 15, 2019, 10:55:47 PM
Hi sorveltaja

Jo or one of the administrators or Ade, should be able to tell us how to send a DXF file to each other.

Mike
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: crueby on April 15, 2019, 11:00:20 PM
As long as they are not too large, cannot dxf files just be attached to a post through the 'attachments and other options' feature?
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Vixen on April 15, 2019, 11:09:57 PM
Hi sorveltaja

This is an attempt to attach two DFX files to this message using Attachments and other options.

The attachments don't show up on the Preview, which threw me, but are attached to the post

Actually, I sent two AutoCAD DWG files by mistake. I will do the DXF's in the morning.

Mike
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 15, 2019, 11:39:32 PM
Mike, thanks. I imported those DWG-files to Rhino with no problem, just for a test. Take your time with DFX's. No hurry at all.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Vixen on April 16, 2019, 11:05:35 AM
Good morning sorveltaja.

Here is the DXF file for my 4 speed and reverse Merritt-Wilson transmission. Unfortunately the overall assembly DXF drawing was too big to send as an attachment, you will have to make do with the DWG file

Mike
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Roger B on April 16, 2019, 05:49:10 PM
Thank you for posting those Wilson drawings Mike  :ThumbsUp:  :ThumbsUp:  :wine1:
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Vixen on April 16, 2019, 06:04:36 PM
My Merritt-Wilson 4 speed and reverse transmission was based on the gearset from Sturmey-Archer push bike gear hubs. You will need three hubs. I chose them because used ones are still available in the UK. They are tough, robust and almost indestructible. I still have a few spare S-A hubs in store. Of course other gear sets could be used, but they would give different gear ratios and their own set of design compromises.

Mike :noidea:
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 16, 2019, 09:09:54 PM
Thanks for the drawings, Mike :)

This is the progress so far:
(http://www.elisanet.fi/kz1706/3d_model_so_far.png)

After I get the modelling done, I think I'll replace the ball bearings with simple brass bushings. On the other hand, they seem to be in metric sizes, so it shouldn't be that hard to source them.

The brake spools are somewhat challenging, what comes to 3d-printing. To prepare them for printing, some of them might need to be splitted, but that's just a part of the thing, that I want to learn also.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: dieselpilot on April 16, 2019, 09:21:04 PM
Did you catch this image in their photo gallery? http://project38.net/wp-content/uploads/IMG_0202.jpg
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Vixen on April 16, 2019, 11:06:22 PM
Hi sorveltaja,

Some quick 3D drawing work there. 4th gear is a direct drive ie. no gear reduction. It is engaged by a dog clutch in my version. You may wish to make it a simpler 3 speed plus reverse gearbox by discarding the red dog clutch disc.

The bearings shown are all metric and readily available on e-bay. there is no need for high quality bearings at the prototype stage, so go for the cheapest available.

If you print the brake spools oversize or split,  do you have lathe facilities to turn them to the correct size and perfectly round and concentric?

The Sturmey-Archer gears have plenty of clearance, so print your prototype gears slightly undersized, so they don't bind.

Mike
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 16, 2019, 11:13:22 PM
Dieselpilot, yes I have seen that image. But as it is just a sketch, it is somewhat difficult to interpret, as there are no exact dimensions of the most important parts, like gears, mentioned.

I tried to model it using their only cad-drawing, that is available on the site: http://project38.net/wp-content/uploads/A001-Transmission-Full2013-BSize.jpg

Maybe I'm missing something crucial, but to me, that drawing is quite sparse, or lacking. I just can't figure out, how the gear sets are linked together (http://emoticons4u.com/crazy/1087.gif)

In the meantime, I'll stick with Mike's drawings, which I can understand.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 16, 2019, 11:39:02 PM
Mike, thanks for the tips. Yes I have the lathe ready to go. When ready for printing, I'll do some test samples first, to see, and set the tolerances. Better bit loose than too tight.

Those ball bearings, I might get them from a local supplier. Have to check the required sizes availability, though. If not suitable sizes available, I'll go to ebay.

Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 17, 2019, 11:08:06 PM
Getting there piece by piece:
(http://www.elisanet.fi/kz1706/getting_there.png)

While going through my junk boxes, I managed to find two ball bearings, that are exactly same size as the ones, that are on both ends(10x26x8). Haven't done the search for the real ones yet, but in the meantime, I printed 'mock-up' -bearings, which don't have any moving parts in them. They need to be turned to proper sizes, though:
(http://www.elisanet.fi/kz1706/mock_up_bearings.JPG)

Today I got seriously distracted by 3d-printed ball and roller bearings. But no matter what form they have, there seems to be always problems with tolerances.

Either whole object is frozen to one lump, or is too loose. There are some, that try steel balls, but it gets very complicated, as there needs to be cage(s) to keep the balls or rollers in certain positions,
like the real ball or roller bearings have.

Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: ddmckee54 on April 18, 2019, 05:49:51 PM
Silly question, but have you tuned the steps/mm on your printer so that when you tell it to print a 20mm cube, you get a 20mm cube?

Before I fixed my first printer it was WAY off, a printed circle was visibly an ellipse.  My second printer was not so bad, but it still needed to be tweaked a little.  If you haven't been printing mating parts you might not have noticed any issues.

Don
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 19, 2019, 12:23:41 AM
Don, not so silly question. I haven't even thought about tuning the printer. When I got it, I started to print the project parts right away.

To be honest, I really didn't expect the printer to be that precise, after all. With standard settings, there is always some extra material, that is then machined away, to match the actual drawings.

Here is a screenshot of the 'control panel' from the Flashforge Finders manual:
(http://www.elisanet.fi/kz1706/control_panel.png)

I'll have to admit, that I have no idea, of how to manage those things.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 20, 2019, 11:25:29 PM
I searched the net about how to fine tune the steps/mm. Tried some freeware programs, but wasn't able to get any of them to connect to my printer through USB.
In fact, those programs don't even seem to have a USB option.

I guess that the programs, that allow the user to take 'full control' of the printers settings, are more compatible with 'open source' printers. Obviously mine is just a plug and play, entry level device.

However, what comes to the project, I had to scale it down about x 0,6. At first, at the original scale, I printed one of the brake spools. Then took it to lathe, and soon figured out, that there wasn't enough
room to attach any cutting tools to cross slide :facepalm2:.  That brake spool has about 65mm diameter, and if memory serves, it must be the largest part, that I have ever tried to machine with my lathe.

For size comparison, big one on the right:
(http://www.elisanet.fi/kz1706/scaled_down_version.png)

While scaling down, I'll also simplify them, and increase the wall thickness of the parts, that are to be threaded for screws, as they are made of plastic after all.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 22, 2019, 01:17:41 AM
After I got the planet gears printed at 'normal' -setting with Flashprint, they were really tight to fit together with ring gears. So I printed one pair of the same gears with 'high' -setting, and still same result.

Tried to fit them by turning the outside diameter down about 0,4mm. Again, too tight fit :headscratch:.

Yet another pair of the gears were printed, and I measured the outer-, and the root diameter. Outer diameter was very close to drawing, while the root diameter, that was supposed to be 7,5mm, was 8,2mm. 

I drew a bogus version of the same gear with 6,5mm root diameter, and printed it. Again, the outside diameter measured ok, but the root diameter was 7,0mm, instead of 6,5mm:
(http://www.elisanet.fi/kz1706/gear_root_diameters.png)

So I decided to take a closer look, of why the Flashprint insist doing that. So far I have found, that it uses 'ffslicer' to do its thing (and create the gcode?).

On the same ffslicer- file folder, there is also a config file, which consist numerous variables, for which I searched documentation on the net, just to find, that there isn't any info available. Got to love the closed systems :smokin2:

As far as I understand, the gcode is, what commands the printer to do, what it does. So maybe there is some hints on the gcode files... I took another look on the net, of how to import gcode files back to 3d-program, to see the actual tool paths, and hoping to modify them, as needed. Results were very sparse. Seems to be yet another 'closed system'.

I installed the Slic3r, as an alternative to ffslicer, but it needs plenty of time to get used to.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: dozerdroid on April 22, 2019, 02:35:40 AM
Sorveltaja, just wanted to thank you for this thread, following closely .. I've always been very interested in transmissions  :D .. Droid. (I have read this site daily for numerous years .. My first post )
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Vixen on April 22, 2019, 12:22:46 PM
Hello Sorveltaja

I have more experience with planetary (epicyclic) gearboxes than with 3D printing so can only offer a guess rather than a positive solution to your printing problem.

As I see it, you make an accurate drawing, some software slices it and more software creates the g-code, yet more software moves the extruder head to print a filament of plastic. The problem appears that you do not know precisely at which stage in the software process the errors occur. Some calibration test prints may help you.

Could you make a drawing and print a cylinder of exactly 25mm diameter, another at exactly 50mm diameter and a third as large as your printer will allow. You can check the g-code to see if it matches the diameters of the three cylinders. You can then measure the printed cylinders for size and roundness. This may help you identify the source of the errors. The errors may be a constant offset error or the error may be proportional to the size of the object. You could try to compensate for the errors in some way once you have identified the source.

Do you know how the software compensates for the width (thickness) of the extruded plastic filament

Mike
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 22, 2019, 11:47:15 PM
Dozerdroid, thanks and warm welcome to the forum :ThumbsUp:

Mike, I made a drawing for the 25, 50 and 140mm cylinders(printing area is max.140x140x140mm), height is 5mm. Well not actually cylinders, more like rings, as the biggest one would have taken over 6 hours to print at 'high' -setting, if it was a solid one:
(http://www.elisanet.fi/kz1706/test_rings.png)

And here are the settings, that I use to print the rings:
(http://www.elisanet.fi/kz1706/slice_parameters.png)

I printed them one at a time. Smaller one's outer diameter is spot on 25,0mm, also height is 5,0mm, but the inner diameter is 14,8mm. Bigger one's outer diameter is again spot on 50,0mm, and height is between 5,0 and 5,1mm. Inner diameter is 29,9mm:
(http://www.elisanet.fi/kz1706/printed_test_rings.JPG) 

Biggest one is still printing, and its inner diameter might be even closer. Generally the z-axis(horizontal) seems to be quite precise, also the roundness of the printed parts is quite good.

Due to the printed surfaces not being as smooth as machined ones, mating parts always seem to need some extra in them, which allows machining for closer fit.

And yes, error(s) seems to be proportional to part's size. That's why I chose quite bulky gear size(mod 1), when scaling down the transmission's parts. Even then, as mentioned earlier, there is some kind of an offset jazz going on with the smaller gear's(suns and planets) root diameter. Ring gears, as they are three times bigger in diameter, are somewhat more precise.

I haven't found an easy way to extract the actual tool paths from the gcode files for editing and measuring. I could do it manually, but after editing, the gcode file should still have a certain structure, as it also seems to contain plenty of commands other than coordinates, for the printer to accept it. Maybe I could do it for a single file, just to see the containing dimensions of the small gear.

But again, it might concern only Flashforge Finder, its bundled software, and probably also its firmware. 

What comes to how the software(Flashprint) compensates for the width of filament, I'm not sure, as the manual doesn't mention it.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: dieselpilot on April 23, 2019, 02:03:29 PM
To maintain a high linear velocity, printers often round corners. This is my guess as to what's happening. Running one of the calibration prints would probably give a good idea of what's happening. Printers handle this in different ways and it have to do with material feeding and/or acceleration rates. I have zero experience with printers, only what I read about in terms of how the controls work. It would also be worth reading up to see what others are experiencing with this particular machine.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Vixen on April 23, 2019, 06:39:10 PM
When I make my planetary (epicyclic) gearboxes, I use hardened steel for the (annulus) ring gear and for the sun and planet gears. All the gears and the gear centre distances for the planet carriers etc, need to be machined to an accuracy in the order 0.025 to 0.05mm (1 to 2 thou) for the gearbox to work successfully. That is why I use or modify commercially available gears such as the epicyclic gears from a Sturmey Archer bike hub, whenever possible.

Each of the planetary (epicyclic) stages must spin freely, without friction. If any of the gears bind or cause friction, it has the same effect as applying a gear selection brake. The Merritt-Wilson planetary (epicyclic) gearbox can only toreate ONE gear selection brake being applied otherwise the whole gearbox will lock up and damage itself.

Precision is therefor a fundamental necessity for planetary (epicyclic) gearboxes, Achieving the necessary precision is a lot to ask from a filament extruder printer. It will be a challenge.

Mike

Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 23, 2019, 11:41:06 PM
Dieselpilot, yes there are plenty of factors involved. When I took a look at the gcode file, there were numerous 'ratio' -commands here and there. Are they there for the extruder - possibly.
I have looked also for other's experiences with Finder, but mostly they just print out the sample boat, and judge the print quality by the looks of it.

There is one video on Youtube, where the user tests the accuracy by printing single planetary gearset in one go, to see, if they can be detached from each other after the printing.
That kind of tests seem to be very rare. Of course, the printer he had was of different brand, and maybe not so 'entry level', as he had updated the extruder, or some of that stuff, before taking it to test.

Mike, thanks for the explanation. To overcome the printer's lack of accuracy, considering the gears, hobbing is what comes to mind. Print the sun- and planet gears a bit oversize, and hobbing takes care of the rest.

For me, making the actual hob is a big question mark, though. Should it necessarily be a cutting tool, or could it be an abrasive one instead, as there shouldn't be that much material(PLA plastic) to be removed after all, in this scale? At a low speed, with some cutting fluid now and then, to allow the debris to flow away, and lessen the friction.

Something like an iron powder impregnated epoxy perhaps, which is then poured to printed mold. But enough of that plan 9 from outer space(http://emoticons4u.com/crazy/134.gif).

The project goes on. I can hardly wait to get it ready to go:
(http://www.elisanet.fi/kz1706/getting_there.JPG)





Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: ddmckee54 on April 25, 2019, 09:57:59 PM
When tuning my printer I cheat, I use gcode commands.

From my machine control panel in Simplify3D I send the M503 command, you can do the same from what ever you are using to run the printer.  That will return the current Steps/mm values for all axis.  That will return values that will look something like this;  X100 Y100 Z400 E100.  When I want to get info out of the printer is the only time I hook a PC up to it.  I normally print from the SD card and use my PC for other things.

If for instance, your X axis is printing oversized, and your Y axis was printing undersized, that would mean that mean that X needs to take less Steps/mm and Y needs to take more.  I'm not going to go through how to calculate the correct values, I'd just get it wrong and make myself look sillier than I already do.

The next thing we need to do is get that information into the printer's brains so it can be put to use.  If you have the correct version of your software and are comfortable with modifying it that way - have at it.  I've been a programmer for years and since I DON'T have the known correct version of the software, I'm too afraid I'll fix one thing and break 12 others if I try that route.

So what's that leave us?  Yup, BRUTE force, we're gonna use gcode.  In particular we are going to use the M92 command to set the Steps/mm.  I add a line similar to the one below into the start-up script that is run every time a gcode file is loaded to the printer:
M92 X90.01 Y110.95 Z400 E100;
I'll keep tuning those values until I get to a point where it's "Good 'nough for gubmint work".  Currently my 20mm cubes are measuring 20.02mmx20.02mmx19.98mm.  I could probably tune it more, but at this point it's "Crose enough".

It doesn't matter which slicer you use, somewhere they are going to give you the ability to send custom gcode to the printer.  I've also done the same thing to tweak the PID parameters, I just can't remember that M command right now.  By downloading these values to the printer every time a gcode file is loaded the default printer values are overwritten with the "tuned" values.  I'm ensured that if a part don't fit - it's because I screwed up somewhere not the printer.

Don
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 25, 2019, 10:27:35 PM
Today I took the transmission to the lathe to spin it for testing. Third and second gears weren't that bad, but first gear was a lot noisier. The reverse gear, where the input shaft's rotational force seems to go through all the other stages or gears, it got really crakling.
(http://www.elisanet.fi/kz1706/snap_crackle_pop.png)

As Mike mentioned earlier, tolerances are extremely important. Even smallest errors in gear's geometry (and noises)multiply at every single stage. I can fully understand, why he sticks to readily available gears.
I'd do the exact same.

What comes to 3d-printed gearsets, I think I'll increase the tooth size next, from mod 1 to mod 1,5:
(http://www.elisanet.fi/kz1706/comparison.png)

There is a caveat, when increasing the tooth size, when needed to fit to certain(small) dimensions, though. Gears with very few teeth start to lose their meshing ability. Somewhere I read, that 13 teeth is an absolute minimum.

As can be seen on the above picture, mod 1,5 planets- and sun gear have only 7 teeth, and look already too 'fat', when compared to mod 1 ones.

But anyways, I'm going to take liberties with that. No matter what form the teeth are going to have, the goal, or at least the aim, is to make a more 'forgiving', full gearset, to keep the noise level down,
while also allowing it to rotate more freely.

Lesser teeth seems to be an option at the moment. And no, I'm not a dentist.

Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 25, 2019, 10:51:38 PM
Don, thanks. I have tried Simplify3D also, but haven't had much luck with it. Somehow it just doesn't recognise my printer at all.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Vixen on April 25, 2019, 11:13:50 PM
Hello sorveltaja

Congratulations for getting this far. A noisy three speed and reverse epicyclic gearbox using printed gears is a real achievement. With any Wilson gearbox, all the epicyclic stages spin at different speeds, The speed of the output shaft is dependant on which gear band brake is selected. First and Reverse gears will the worst as the overall reduction is the highest and reverse has a direction change as well. Some of the epicyclic stages will be spinning really fast.

What's you reasoning for going from 1.0 Mod to 1.5 Mod?

My instinctive reaction would be to increase the tooth count to reduce the tooth meshing noise, unfortunately reducing the tooth size also increases the precision required.

It is normal practice to have three planet wheels, instead of just the two. This will have the effect of increasing tooth count as well as improving the load distribution and concentricity of the sun and  planets, as they spin inside annulus gears.

Do you have an end use for your epicyclic gearbox or is it simply an exercise in design and 3D printing?

My Merritt-Wilson transmission system was designed for use in a 45Kg 1/6 scale, all metal, model tank (AFV) driven by a 2HP four stroke petrol engine. The Sturmey-Archer bike gear hubs provided the epicyclics for both the Wilson gearbox and for the Merritt double differential track steering. The S-A bike hubs selflessly donated their internal organs for scientific purposes. They proved to be a strong and very robust solution. They were also quite noisy, but then, so is any tank.

Mike
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Vixen on April 25, 2019, 11:58:18 PM
Hello sorveltaja

I found some photos of the Sturmey-Archer epicyclic gears.

These are the sun, planet and annulus (ring) gear as removed from the bike hub but before any modifications. You can clearly see that there are four planet gears inside the planet carrier housing. The extra planet wheels improve concentricity and load sharing.
(http://lister-engine.com/coppermine/albums/userpics/10013/S-A1.JPG)


Here I have installed the four plant wheels inside a new planet carrier housing and have cut the annulus (ring) gear free using an abrasive cut off disk in a Dremmel  The annulus is mounted on a new aluminium carrier containing a bearing and a toothed belt drive gear. These components are configured as a steering differential on a 1/6 scale all metal model tank.
(http://lister-engine.com/coppermine/albums/userpics/10013/S-A2.JPG)

This is the final assembly of the Sturmey Archer epicyclic stage used as a steering differential on a 1/6 scale all metal model tank.
(http://lister-engine.com/coppermine/albums/userpics/10013/S-A3.JPG)

Your illustrations only show two planet gears for simplicity, three or four planet gears are more normal.

Mike
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: ddmckee54 on April 26, 2019, 08:17:06 PM
I think you said that you're using Slic3r?  I always had trouble with Slic3r and outer dimension stability.  It's been a while since I used Slic3r, but if I remember correctly I had better luck with it when I fixed the filament width at the value of the nozzle width.

My theory at the time was that a nozzle is NOT going to extrude a filament that is less than the width of the nozzle opening.  I think that Slic3r is calculating the filament width based on a percentage of layer height as a default setting.  A filament width calculated on a layer height less than 0.4mm will give a filament width of less than 0.4mm.  If you're actually printing a 0.4mm wide ribbon and the software says the width of that ribbon is 0.2mm that extra material has to go someplace.  I don't know if that's correct or not, won't be the first time I was operating on an incorrect assumption.

Out of idle curiosity, what do you mean when you say Simplify3D doesn't recognize your machine?

Don
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 27, 2019, 12:05:37 AM
Don, my bad. I must have been mixing Simplify3D with some of the freeware ones that I've tried. I don't have Simplify3D. I have only read about it. Sorry for the confusion.
Information, that you have provided, is much appreciated, though.

Hello sorveltaja

Congratulations for getting this far. A noisy three speed and reverse epicyclic gearbox using printed gears is a real achievement. With any Wilson gearbox, all the epicyclic stages spin at different speeds, The speed of the output shaft is dependant on which gear band brake is selected. First and Reverse gears will the worst as the overall reduction is the highest and reverse has a direction change as well. Some of the epicyclic stages will be spinning really fast.

What's you reasoning for going from 1.0 Mod to 1.5 Mod?

My instinctive reaction would be to increase the tooth count to reduce the tooth meshing noise, unfortunately reducing the tooth size also increases the precision required.

It is normal practice to have three planet wheels, instead of just the two. This will have the effect of increasing tooth count as well as improving the load distribution and concentricity of the sun and  planets, as they spin inside annulus gears.

Do you have an end use for your epicyclic gearbox or is it simply an exercise in design and 3D printing?

My Merritt-Wilson transmission system was designed for use in a 45Kg 1/6 scale, all metal, model tank (AFV) driven by a 2HP four stroke petrol engine. The Sturmey-Archer bike gear hubs provided the epicyclics for both the Wilson gearbox and for the Merritt double differential track steering. The S-A bike hubs selflessly donated their internal organs for scientific purposes. They proved to be a strong and very robust solution. They were also quite noisy, but then, so is any tank.

Mike

Mike, the reason for going to 1.5 mod was simply to see, how much more there is room to play with offsets. When printing gears, they will not be as accurate as machined ones.

So all kinds of eccentric defects are always present. To overcome that, I increased the tooth size, so there is bit a better chance to avoid the collision of one gear's teeth's outer diameter(slightly eccentric), with other gear's root diameter(also slightly eccentric). I wish I could explain that better.

Instead of just two planet gears, I have added two more. With 21 teeth ring gear, and 7 teeth planet gears, to my surprise, four planet gears seem to fit, or mesh together with sun gear and ring gear.
But I'll have to confirm that, by printing them out first. I have even drawn 1.5 mod helical gearsets, but wouldn't hold my breath for them to be less noisier.

What comes to my take on epicyclic gearbox, It's more like an exercise to realise a model, that could hopefully end up as a usable project for others, that are interested of planetary gearbox, and its magical movements.

Of course, the gear changing mechanism is an open question so far. But I'll get back to that, after I get the gearset problems sorted out.

And Mike, that tank project seems quite interesting :praise2:. What could be better, than putting the four cycle engine, coupled with an automatic transmission to actual use??
Do you have a build blog of that tank?

And thanks for the additional pictures of the Sturmey-Archer gears.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Vixen on April 27, 2019, 04:45:47 PM

Mike, the reason for going to 1.5 mod was simply to see, how much more there is room to play with offsets. When printing gears, they will not be as accurate as machined ones.

So all kinds of eccentric defects are always present. To overcome that, I increased the tooth size, so there is bit a better chance to avoid the collision of one gear's teeth's outer diameter(slightly eccentric), with other gear's root diameter(also slightly eccentric). I wish I could explain that better.

Instead of just two planet gears, I have added two more. With 21 teeth ring gear, and 7 teeth planet gears, to my surprise, four planet gears seem to fit, or mesh together with sun gear and ring gear.
But I'll have to confirm that, by printing them out first. I have even drawn 1.5 mod helical gearsets, but wouldn't hold my breath for them to be less noisier.


What comes to my take on epicyclic gearbox, It's more like an exercise to realise a model, that could hopefully end up as a usable project for others, that are interested of planetary gearbox, and its magical movements.

Of course, the gear changing mechanism is an open question so far. But I'll get back to that, after I get the gearset problems sorted out.

And Mike, that tank project seems quite interesting :praise2:. What could be better, than putting the four cycle engine, coupled with an automatic transmission to actual use??
Do you have a build blog of that tank?

And thanks for the additional pictures of the Sturmey-Archer gears.

Ok, I understand your reasoning; bigger gear teeth will potentially have less percentage error. Let's hope the extra planet wheels do not make the clearances too tight again. You could always revert to two planets if necessary.

The Wilson gearbox was not an automatic gearbox. The next gear was preselected by the driver, when the clutch pedal was pressed, it engages the brake for the previously selected gear. My model uses a centrifugal clutch (automatic-ish) and for the Wilson gearbox, I intended to use a four lobe camshaft operated by a single servo. The cams would have been located 90* apart and each cam would operate one of the band brakes to select that gear ratio.

I have not posted a build log in the MEM website. I did not think a scratch built, model tank with a multi speed transmission and double differential steering system was appropriate for this forum dedicated to Model Engine Making; I did not expect there would be much interest in the subject matter. There would probably have been more interest if it had been powered by a boiler and steam engine built from castings.

Mike
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Kim on April 27, 2019, 05:43:02 PM
I would have been (am!) interested! Sounds like an engine powered vehicle to me!
Kim
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 27, 2019, 10:08:01 PM
Here are the first parts of the mod 1.5, helical gearset. Reverse brake spool with an 'orphan' sun gear, to see how they fit together:
(http://www.elisanet.fi/kz1706/helical_gearset.JPG)

Ring gear has 0,3mm offset, planet gears 0,1mm, and the sun gear was scaled down to x 0,95. When fitting them together, there were still some tight spots.

So I turned 0,2mm off of the planets- and the sun gear's outer diameters, and tight spots went away. There are relatively big gaps between the gears, but still enough meat in them to mesh together(although loosely).

Now the reverse brake spool and its gears rotate freely. No more crackling, only rattling. But as there is a play between the gears, which also have somewhat rough meshing surfaces, noise is to be expected.

With previous version of the transmission, which had plenty of friction, and some serious bindings and tight spots, I applied plenty of white vaseline to gearsets.

Messy stuff, but it seemed to dampen the noise to some extent.

Due to the printed parts being partly hollow, they act like acoustic amplifiers. I have printed the parts with 50% infill for some time now, in hopes to reduce the noise factor. 

But once I manage to make a low friction version of the transmission, I'll print all the parts once again with 100% infill.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: ddmckee54 on April 30, 2019, 05:56:07 PM
3D printers, at least the AFFORDABLE ones, will never give a smooth surface finish so that is going to contribute to your noise also.  Your statement that your printed gears bind in some spots make me think that not all of your axis are printing accurately.  If your X and Y axis are not printing the dimensions you tell them to print then you're not going to get circular gears.  They'll be elliptical, which will contribute to both binding and noise.  Z axis dimensional accuracy will always be a problem, unless you are so lucky or good that the top of your part always corresponds to the top of that layer.

I've found that even though both my X and Y axis were originally set to the same steps/mm, when I printed my 20mm test cube, the X and Y axis did not print a 20mm object.  On one printer they were within a couple of tenths of a mm, on the other it was more like 0.6mm.  That error will only increase as print size increases, that's why I "tuned" my printers.  Now when I print my 20mm test cube I consistently get values of around the 20.02mm for both the X and Y axis, Z is holding at about 19.98mm, that's good enough for me at this point.  In the future I may try to squeeze another decimal place out of it, but for now it's close enough.

Don
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on April 30, 2019, 11:32:42 PM
Don, how do you actually do the tuning of the printer(steps/mm)? I haven't found any information, of how to tune the one, that I have.

What comes to the 1.5 mod version of the transmission, I think I'm going to redraw the parts, that have bearings, to add some more, and maybe extra bushings, if needed.

Some of my ancient projects just might have practically unused 13 x 6(od x id) ball bearings to donor for the cause. I'll have to check that out, though.

So far my take on the original drawings has been rather clunky, as I wanted results as soon as possible(http://emoticons4u.com/crazy/1261.gif).

I know that (https://madmodder.net/Smileys/default/worthless.gif)

I'll be posting pics of the progress, as it proceeds.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: ddmckee54 on May 02, 2019, 10:52:59 PM
Like I said in Reply #39, I cheat.  I documented the steps in that reply.  A couple of things I didn't say was that I printed a 20mm test cube with X,Y, and Z on the appropriate faces so that I would know how the cube was oriented  when it was printed.  Also you need to use a micrometer for the actual measurements.  A digital caliper will get you sorta close, but you need more accuracy than that.

Don
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on May 03, 2019, 12:17:56 AM
Don, yes I had to look again, and there it was in the reply 39. I started to wonder, how to make the information, that moves between computer and the printer, visible.

As it is through usb, it was easy to find a software, that shows a 'raw data view', from https://freeusbanalyzer.com

The only way so far, that I've managed to send M503 -command to the printer, is to make a new .g-file(actually a text file), which consist only that command. Then opened it with Flashprint, and hit the print -button.

Extruder and the plate made some moves. After they stopped moving, I ended the capture.

That usb-analyzer was already running, and capturing the usb traffic only for selected device, which was the printer. It was possible to export both 'read' and 'write' -data to text files.

Here goes the 'read' data:
Code: [Select]
CMD M602 Received.
Control Release.
ok
CMD M601 Received.
Control Success.
ok
CMD M602 Received.
Control Release.
ok
CMD M601 Received.
Control Success.
ok
CMD M650 Received.
X: 1.0 Y: 0.5
ok
CMD M115 Received.
Machine Type: Flashforge Finder
Machine Name: Flashforge Finder
Firmware: v2.2.7.299 F2.12.2 20181203
SN: FFF215029
X: 140 Y: 140 Z: 140
Tool Count:1
ok
CMD M114 Received.
X:-64.9991 Y:-64.9991 Z:70 A:0 B:0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: READY
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M28 Received.
Writing to file: 0:/user/testi.g
ok
CMD M29 Received.
Done saving file.
ok
CMD M23 Received.
File opened: testi.g Size: 5
File selected
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:27 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:27 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:27 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:27 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:27 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:27 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:27 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:27 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:27 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:1 Y-max:0 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:1 Y-max:0 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:1 Y-max:0 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:1 Y-max:0 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:1 Y-max:0 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:27 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:1 Y-max:1 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:27 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:1
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:27 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:27 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: BUILDING_FROM_SD
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M26 Received.
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: READY
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:27 /0 B:0/0
ok
CMD M27 Received.
SD printing byte 0/1000
ok
CMD M119 Received.
Endstop: X-max:0 Y-max:0 Z-max:0
MachineStatus: READY
MoveMode: READY
Status: S:1 L:0 J:0 F:0
ok
CMD M105 Received.
T0:26 /0 B:0/0
ok

And the 'write' data:
Code: [Select]
~M601 S0
~M602
~M601 S0
~M650
~M115
~M114
~M27
~M119
~M105
~M28 5 0:/user/testi.g
~M503~M29
~M23 0:/user/testi.g
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M119
~M105
~M27
~M26
~M119
~M105
~M27
~M119
~M105

The printer seems to respond to M503 -command, but I can't figure out, what it does with it.

In Slic3r, there is an option to add a custom gcode to the start and to the end of the code. I haven't been able to connect it to the printer, though. The usb/serial connection box is always empty:
(http://www.elisanet.fi/kz1706/slic3r.png)


   


Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: ddmckee54 on May 03, 2019, 03:33:17 PM
From the files that you sent I have no clue either, I'm seeing what appear to be mcodes that I've never seen before.

I've got a feeling that our printers are using different communications protocols, so let's start with the basics:

1) What printer do you have? (Make & model)
2) How do you get the gcode file to the printer, sent from PC via USB, loaded from SD card, or something else?

I've got a feeling that I'm telling you to send Apples to your machine and it's reading it as Oranges.

Don
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on May 03, 2019, 07:49:52 PM
The printer is Flashforge Finder V2.0.

I send the gcodes, using the bundled Flashprint, through usb cable to the printer.



Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on May 05, 2019, 11:29:53 PM
A bit of a progress. The reverse spool got an extra cover, that also holds the brass bushing:
(http://www.elisanet.fi/kz1706/rev_spool.JPG)

While fitting reverse- and first spool together, all went well, until it was time to fasten the grub screw of the carrier inside reverse spool, to the output shaft.

After some head scratching, the solution was easier, than I thought. I Drilled 2,5mm hole through the rev. spool, so the hex wrench could be used through that hole, to fasten the carrier.
Needed only to dial in the position, and the job was done. The 2,5mm hole was then tapped for M3 grub screw, to keep the lubrication inside:
(http://www.elisanet.fi/kz1706/problem_solved.JPG)

And here was another puzzle, of how to connect the second spool's inner spool to first spool. Obviously, both ends of the carrier stubs couldn't be threaded ones.

Stubs have 4mm blank ends, while first spool's cover has 5mm holes in it, to allow less critical operation:
(http://www.elisanet.fi/kz1706/from_1st_spool_to_inner_2nd_spool.JPG)

Now the second spool's cover has a brass bushing:
(http://www.elisanet.fi/kz1706/2nd_spool_bushing.JPG)

First spool's cover will also have one. Not sure, if they are of any help, but hopefully they make the construction more rigid.

Last but not least, is the dirty trick, that I tested on one of the scratchy gearset. In fact, they are all scratchy straight out of the printer.

I have tested it only with PLA. But here it goes. When running a single gearset at a time in the lathe, or any other power source, holding the brake spool, instead of applying lubrication first,
squirt some acetone to rotating gears:
(http://www.elisanet.fi/kz1706/dirty_trick.JPG)

Not much is needed. When the gears are rotating, you can hear, after applying acetone, change of the sound(or noise) they make. At first, it smoothens, then, quickly after the acetone evaporates,
they get really sticky.

Just before that, apply some lubrication. Otherwise you'll end up prying the gears apart. If successful, gears should have less noise. Repeated treatments, that's something I'm still working on. 

The idea for that came from Youtube video, where a guy tested, if it's possible to glue PLA parts together without glue, using only acetone. He managed to get rather positive results.

There are also some videos, where acetone vapours are used to smoothen out printed PLA surfaces. Not very convincing, though.

As far as I understand, PLA is not soluble in acetone, but it seems to have some factor in it, that softens the surface of the printed PLA part, making it just slightly more 'malleable'.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on May 08, 2019, 10:53:33 PM
So the Wilson gearbox is mostly completed, although I haven't made the brakes for it. Brass bushings seem to reduce wobbling quite well, and add some rigidity, but otherwise making the whole construction stiffer to rotate.

If I had an extra machine, I would run it for days, or long enough to 'break in' the transmission, to smooth it out:
(http://www.elisanet.fi/kz1706/wilson_gearbox.JPG)

Especially the reverse gear needs more torque, when compared to other gears. But that was also the case on previous version, which didn't have any extra bushings.

I wonder, if the Wilson gearbox was originally intended for slow rotation only, as on some gears, the planets rotate at wildly high speed, when compared to input shaft speed.

Anyways, thanks goes to Mike, who provided the drawings for Wilson gearbox :ThumbsUp:. 

Journey continues, and I looked back to the original sources(or at least one of them), and found Pol Ravigneaux's patent 2,631,476, from 1953. It includes some variations of this:
(http://www.elisanet.fi/kz1706/Ravigneaux_patent_1.png)

I've done sketches to 3d-model the above transmission, to figure out different 'organs' better. To me, the text on the patent is plain, and understandable.

Just as if that wasn't enough of challenge, I found a very highly detailed 3d-model of "Mercedes Classe CLK kompressor 200" automatic transmission at: https://grabcad.com/library/mercedes-speed-automatic-transmission-by-solidworks

It is an absolute overkill, but what the heck. I'll crop out all the outer parts, to the bare bones, just to see if I can find any similarities with Ravigneaux transmission.

Of course there must be plenty of 'flavors' other than Ravigneaux. But one at a time, as it goes.

Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Vixen on May 09, 2019, 12:04:10 AM
Hi sorveltaja

I am pleased you managed to get my Wilson gearbox design to run with 3D printed components.  :ThumbsUp: :ThumbsUp: I had intended to build mine from hardened steel Sturmey Archer bike gear sets.

Have you measured, counted, or calculated the gear reduction ratios for the three forward gears and the reverse gear? I would be specially interested in the reverse gear ratio.

Mike
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on May 09, 2019, 10:59:59 PM
Mike, I put a on mark on both input and output shaft to count the ratios.

1st gear ratio is ~0,33. For one revolution of output shaft, input shaft rotates 3 times (1/3)
2nd gear ratio is ~0,25 (1/4)
3rd gear ratio is ~0,44 (1/2,25)
Reverse gear ratio is ~0,125 (1/8)

All the sun- and the planet gears have 7 tooth in them, and all the ring gears have 21 tooth in them.

But on the other hand, I got an idea of how to measure the ratios bit more precisely, without math calculations. If one had a 360 degree protractors attached on both input- and output shafts, the result could then be more easily read.

There is some slack between the 3d-printed gears though, so it might make the result again less precise, after all.

But then again, to get the exact results, one has to use the underlying mathematics, which makes me feel dizzy.

Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on May 14, 2019, 11:44:03 PM
It's been quiet for a while, but in the meantime I have looked at some different types of transmissions.

As mentioned earlier, the Mercedes transmission was one of them. But it is way too advanced for me to make sense, although I can distinguish sun-, planet, and the ring gears, and their carriers.
Even when most of the outer parts are stripped out, it looks like this:
(http://www.elisanet.fi/kz1706/mersu_gearbox.png)

Then it was time to take a deep breath, and go back for simpler models. I reread this thread from the beginning, and thanks for Ade, who posted(reply #3) link for the page, which also has a video of an animated operation of a gearset.

I simply looked the video many more times again, and counted all the teeth of the involved gears, and modelled them. Result:
(http://www.elisanet.fi/kz1706/gearbox.png)(http://www.elisanet.fi/kz1706/gearbox_inside.png)

I took screen captures from the video to compile a single picture, of how the different elements work together. To me, it explains more than thousand words:
(http://www.elisanet.fi/kz1706/gearbox_.png)
 

As explained in the video, the gears are engaged by using corresponding clutches. There is probably a very good reason for that.

But then I started to wonder, if there was a way to use brakes, instead of (complex?)clutches.

Adding a single planetary gearset for each gear just to engage them by using brakes - not sure at all, if it's any simpler. I might try it, anyways.

I've also revisited the transmission, that was in my first post in this thread. Had to re-draw most of the parts, mostly to add 3 or 4 planet gears, instead of just two.

Other modifications, so far, include something as obvious like this, where the ring gear Z isn't supported in any way:
(http://www.elisanet.fi/kz1706/ring_gear_without_support.png)

Here the ring gear Z has an additional supporting part(highlighted):
(http://www.elisanet.fi/kz1706/ring_gear_Z_support.png)





Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: ddmckee54 on May 20, 2019, 06:00:31 PM
sorveltaja:

If you are still interested tuning your printer, here's something you might think about trying.  When I got my Utilimaker and wanted to tweak the steps/mm settings I couldn't find them listed in any of the available menus on the machine.  I downloaded Mattercontrol from Matterhackers to be able to directly control the printer from my PC.  It's a free 3D printer interface, I checked and it's compatible with Flashforge 3D printers.  Using Mattercontrol I was able to connect to my printer through the USB, send the M503 command, and the printer replied to Mattercontrol with the results.  It's kind of silly but the only purpose that Mattercontrol has been used for by me was to get the settings out of the printer using the M503 command.

Don   
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on May 21, 2019, 08:22:59 PM
Thanks, Don. But I couldn't get the Mattercontrol to install correctly. Problem is the newer version of the .net framework, that it requires to run. It just doesn't want to install. There is always errors.

I spent most of the day trying different ways to get it to install. I don't seem to be the only one with problems of installation of .net framework version newer than 4, though.

I ended up removing older versions of it, and managed to make a mess. Programs that required those older versions, didn't run anymore. So I tried to install them back again, but that didn't work either.

As much as I'd like to test Mattercontrol, I had to give up. I had some older system image, which I used to replace the screwed windows partition.
   
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: ddmckee54 on May 22, 2019, 03:20:10 PM
I feel your pain.  Don't you just love software upgrades that fix some things and yet break others?

At work, we've got a software package that collects utilities usage - gas, steam, electric, etc.  This software requires a version of Java that is well...  let's just say several versions out of date.  Replacing this software would be a massive project since the new version is not compatible with all the hardware that we have installed, and there's a LOT of hardware installed.

There are several key players in the company that require this software for the monthly financial statements.  Whenever those people get a new computer we have to be sure and install that old version of Java.  The computer doesn't even have to be using the older version of Java, it just has to be installed.

Yup, I know what you just went through, been there - done that!

Don
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on May 23, 2019, 01:23:56 AM
Yes it can be quite frustrating, when those things happen. Something like 15 years ago, things were a lot simpler, what comes to windows. As the technology gets more and more advanced, so does the problems involved also, unfortunately.

What comes to Mattercontrol, it seems to have a Linux version also. In the past I used to fiddle with linux just to see, how far I can get with it.

Mostly to see, if I can get all the devices to work, that work in windows. And to test different 'windows only' -programs with wine(emulator).
Luckily there are plenty of documentation, but it sure needs a serious dedication to dive in to that deep subject.

After all these years, I might give it a shot, and try something like Linux mint.

But anyways, back to the original subject. I have scaled the transmission down to half the size, which makes the gears to about mod 0.5. To compensate the printer's tendency to exaggerate the outer dimensions, I've scaled the planet gears down also, so far, that they just fit in. With scale factor 0.97, there is still some tightness.

Scaling the planet gears down seems to work a bit better than using offset, for some reason.

Here is the comparison:
(http://www.elisanet.fi/kz1706/smaller_gears.JPG)

Maybe I finally get my head around the idea of using smaller tooth size instead of bulky one. If the gears are ideally seen as plain rollers, what can be closer to that, than the smaller tooth size?

Basically, I guess, that the tooth size could be as small as possible, as long as the gears mesh together, and therefore provide required ratios.

The original version of the printed transmission uses mod 1 gears(picture above), but should be a breeze to redraw it with mod 0.5 gears.



Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: ddmckee54 on May 23, 2019, 07:43:19 PM
What's the actual size of the 1/2 scale transmission?  Past a certain point it doesn't matter what it looks like on the screen, our FDM 3D printers aren't physically capable of printing the object.  I've got a feeling that your small gears may be approaching that limit.

Our glorified hot glue guns can only do so much.

Don
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on May 24, 2019, 01:12:54 AM
Here are the smallest gears and the largest spool:
(http://www.elisanet.fi/kz1706/small_parts.png)
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: ddmckee54 on May 24, 2019, 10:01:55 PM
How thick are the gear teeth at the minor diameter for the 6.54mm gears?  When objects get small enough your slicing software will start taking liberties with how the part is actually printed.  The software will simplify the perimeter it thinks the perimeter's too small, sometimes it simplifies it a lot.

I've printed 12 sided shells that held M3 nuts at about the dimension of your gear and they came out OK.  Then again I've tried printing features smaller than that and they just came out looking like a mostly unrecognizable blob.

Good luck on your gears.

Don
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on May 25, 2019, 03:01:07 AM
Here is the thickness of the teeth at the root diameter, which of course isn't that precise, when the gear is printed out:
(http://www.elisanet.fi/kz1706/small_gear_2.png)

Reason for me going to that half size transmission is simple - testing. Printing all the parts with 100% infill takes a lot less time.

Why 100% infill then? To lessen the noise of the gear box. No matter how well you 'post process' the printed parts by machining, or by other means, there seems to be always hint of eccentricity involved.

To minimise that, I've played with scaling and offsets, for the gears to have a smoother meshing, and less friction.

All that matters less, if you are aiming for a hand-cranked model of the transmission.

But that's not, what I'm after. I'm in for a model, which could hopefully be operated by something more constant power source, like an electric motor, and perhaps some load on the output side.

I'm looking forward to get to the gear changing mechanism, once I get the other parts of the transmission finished.
 

 
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: AOG on May 25, 2019, 06:12:53 AM
I just noticed this thread and I had some of the same issues as you are having. First of all I have a flashforge creator pro. It uses something called x3g which is not G code. I suspect your printer does to. The other thing I found out is that the line width is set by the diameter of your nozzle. .4 mm seems the be the standard size for most nozzles. As I understand it, with the extruder set to the normal rate you will get a line at nozzle width with the height that you selected. Supposedly you can vary the width somewhat by increasing or decreasing your flow rate.  With the size of your teeth and a .4 nozzle, you are going to have problems approximating the shape. You might to consider changing from involute to cycloidal gears. They may be easier to reproduce at that size.

Tony
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on May 26, 2019, 12:15:45 AM
Thanks for the tips, Tony. I found an online 'Cycloidal Gear Builder' http://hessmer.org/gears/CycloidalGearBuilder.html

So I generated a 0.5 mod pinion with 12 teeth, and printed it out. Its size is quite close to that 'normal' 12 teeth gear. But the printed pinion had some of the spaces between teeth filled, and also had some blobs on the outer surfaces.

Then I took a look of flashprint's settings on the 'expert mode', and found the extrusion ratio, which is 109% by default. Maybe that's the flow rate adjustment ?
(http://www.elisanet.fi/kz1706/flashprint.png)

I changed the extrusion ratio from 109% to 100%, and printed the pinion once again, But still the same results. Reason for that might be, that the pinion has a lot thinner teeth at the root diameter:
(http://www.elisanet.fi/kz1706/pinion_vs_involute_gear.png) 

I have just reached the limit of my printer, I guess.

Nevertheless, the idea of using cycloidal gears is interesting, as there seems to be way more tolerance between the gears(pinions and wheels), than with involute gears.

It could, or should be more forgiving, what comes to slight eccentricity, which the printed parts always have, thus eliminating some of the cumulated friction(and noise), which definitely occurs in every printed, multi-stage geared devices.

To verify all those fancy claims, there is only one way for me to go - print and test. But not with mod 0.5, no. More like 0.75, or better yet, mod 1.0 to make sure, that the printed gears have valid shapes.

The original gearbox has already mod 1 involute gears, so there is no need to start drawing from the scratch.







Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on May 28, 2019, 12:57:32 AM
Before going more into the cycloidal gears, there is still the small transmission, which doesn't rotate smoothly enough to make it a good working model:
(http://www.elisanet.fi/kz1706/05_mod_parts.png)

It is almost impossible to iron out all the eccentricity, that the gears have. But there is one more thing, that I haven't tried yet - hobbing(sort of).

They are mod 0.5 gears, and at least the planet- and sun gears could be hobbed. I just rediscovered the set of cheapo mod 0.5 gear cutters, that I have. I picked the one, that is for 12-13 teeth gears:
(http://www.elisanet.fi/kz1706/05_mod_gear_cutter.png)

Then it was attached to the lathe tool post, so that it can cut a teeth shaped grooves like this:
(http://www.elisanet.fi/kz1706/nylon_hob_test.png)

They are just straight grooves on a 40mm nylon bar. The grooves measure like this:
(http://www.elisanet.fi/kz1706/hob_testi.png)

It was just a test to see how the gears meshed with the 'hob'. So far so good. But I prefer metal, so I'll make another hob out of 25mm round aluminum bar to make sure, that it retains its shape.

But what is a hob without cutting teeth? Maybe not a hob at all, but the one that uses friction to push the material away from the PLA-plastic gears, hopefully

Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: ddmckee54 on May 28, 2019, 09:00:16 PM
You're going to have a hard enough time trying to machine the gear teeth by cutting them, I believe that trying to use friction to push the plastic around is just asking for delamination problems. 

The extrusion ratio is the variable that the slicing software uses to modify the calculated extruder feed rate.  Not knowing how Flashforge handles the extruder feedrate calculation we don't know the exact mechanics of this calculation.  We do know that the feed rate will be based on the volume of material required for each printer move taking the length of filament required for the move, the printer speed, the filament width, and the layer height into account.  With the ratio setting at 109% you were telling the printer to constantly extrude 9% more filament than it thinks it needs.  Over-extruding is handy on the 1st and last layers to get a smoother finish on the surface.  For all the rest of the layers, that extra filament had to go somewhere which might account for some of your dimensional variation.

Your minimum feature size is going to be determined by the width of the filament being extruded, I'm guessing that would be your Path Width setting.  It looks like this is a "fixed width" setting.  No matter what the layer thickness the filament width will always be this value.  For comparison, Slic3r defaults to a filament width that varies with the layer thickness, but it can be set to a fixed width.  With your current 0.4mm Path Width setting, I'm guessing that what you would actually get when you try printing these 0.7mm wide gear teeth will be a single 0.4mm wide straight sided feature.  At a 0.4mm path width, the slicing software cannot fit a continuous perimeter around the object, that would require minimum width of at least 0.8mm, so the teeth would be printed as a single 0.4mm wide line.

I have YET to find a slicing software that fully explains what modifying the individual settings will actually do.  Sometimes you just have to play with the settings to find out what they will do.

Don
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on June 01, 2019, 02:07:32 AM
Don, you are right. Result of the friction hobbing:
(http://www.elisanet.fi/kz1706/hobbing_result.png)

There is one thing, that I noticed, when printing smaller mod 0.5 gears. All of them are ok on the right side, but the left side has constantly a lot of defects, no matter if they are printed one at a time, or three or four at a time.
(http://www.elisanet.fi/kz1706/gear_defects.png)

I'm tempted to go different route, and machine all the planet- and sun gears from the blanks of pla, or other kind of plastic. But that's not the way to make a working model of the transmission, which should be easily reproduced, as many, who are interested, don't have access to all the machines and the tools, that it requires.

I have machined only few gears in the past out of metal, and the amount of the work needed was/is daunting. My humble greetings to all those, who machine their gears out of metal.

That's why I'm going to move to mod 1.0 cycloid gears. I Did some test prints, and the resulting gears had correct shapes, without visible defects.


 
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on June 01, 2019, 10:44:49 PM
Instead of going straight to mod 1.0 teeth size, I started to wonder, what is the actual smallest teeth size, that my printer can print cleanly. So I printed some mod 0.6 cycloidal gears, and to my surprise, this was the result:
(http://www.elisanet.fi/kz1706/mod_06_cycloidal_gears.png) 

The ring gear spool has some pitting on the uppermost layer, but the teeth are just fine. No blobs or other defects on the smallest gears. Of course they have small 'skirts' on the lowermost part, that are easily trimmed away in the lathe. But then again, all the parts, even though they are printed without brim, have skirt in them.

Easier workaround could be to print the gears something like 1mm taller, and then simply sanding them to desired length, thus removing the skirt also.

Little about the shapes of the cycloidal gears - especially ring gears. As mentioned before, I use "Cycloidal Gear Builder" at http://hessmer.org/gears/CycloidalGearBuilder.html

There isn't an option to build ring gears, but I simply built a 'wheel' -gear, which had the same amount of teeth, that the desired ring gear has. It had to be modified a bit, though. I took one tooth apart, and mirrored it to replace inwards pointing teeth:
(http://www.elisanet.fi/kz1706/cycloidal_ish_ring_gear.png)

On the left is the original shape, and on the right side is modified one. The original shape seems to have already some tight spots with pinion gears.

Just another scetch, where the tips of the inwards pointing teeth are replaced with round shapes. But that one could have tight spots as well:
(http://www.elisanet.fi/kz1706/cycloidal_ish_ring_gear_2.png)

One more thing, that I tested. Does the quality of the prints increase, if you make the objects surface 'finer', by dividing it to more smaller surfaces, like this:
(http://www.elisanet.fi/kz1706/finer_surface.png)

Answer is simple - yes to a certain point. The simpler gear on the left is about 40kb in size, when exported to stl-file. The gx-file is about 310kb.

Then I went overboard with the gear on the right side. I started to divide its surface, resulting larger and larger stl- and gx-files(megabytes). At the end I had a 52Mb stl-file.

But no matter how big and detailed the stl-file was, the slicer(at least on flashprint) created a gx-file, that was never over 7-something megabytes. Again one mighty limit, but it could be about the resolution of the hardware of the printer itself.

"Printer's got to know its limitations", as Clint Eastwood would have said it.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: ddmckee54 on June 10, 2019, 06:12:53 PM
sorveltaja:

The small skirt that you mentioned is sometimes referred to as an "elephant's foot".  This is caused by your print head being slightly closer to the print bed than was intended - "smooshing" the 1st layer filament wider than it should be.  You might for instance be intending to print a 0.3mm 1st layer, but the print head could actually be at 0.25mm.  I'll bet you're getting really great bed adhesion though aren't you.  The simplest thing to do is tweak the position of your Z axis limit, raising the print head a fraction of a mm.  You'll need to find the Z axis sweet spot where you're getting good 1st layer bed adhesion, and yet not getting any "elephant's feet"

As far as the top layer "pitting" is concerned, the fix for that might be as simple as increasing the number of top layers that are printed in you slicing setup.  In order to get a good solid top layer, I usually print a minimum of 3 top layers.  It sometimes takes a couple of layers just to close up the gaps before you'll get a solid infill.

Don
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on June 11, 2019, 12:34:47 AM
Don, yes I tend to calibrate the build plate rather close to the nozzle(under 0.10mm). I do it manually, as I've found that the automatic calibration in Finder is useless.

As you mentioned the bed adhesion, it is indeed quite good, even though the Finder doesn't have warmed build plate. I might do some testing about the top layer and 'elefant feet'. Thanks for the tips.

What comes to the transmission, it is still far from perfect, but here is the mock-up of it with middle support:   
(http://www.elisanet.fi/kz1706/middle_support.JPG)

There is something strange between 3rd and 4th gears though, which I haven't been able to trace so far. It feels like they are missing. Maybe it is too obvious for me to see:
(http://www.elisanet.fi/kz1706/gearbox_3.jpg)

At the lower left corner there is a diagram of 'kraftfluss'(power flow?), but I'm not sure, how to interpret it.

Anyways, here is the drawing of current version of the transmission:
(http://www.elisanet.fi/kz1706/gearbox__.png)
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: jtrain on June 11, 2019, 05:16:25 AM
This is not a transmission but someone that made planetary gears for a different purpose.

e1uR8Cr22rA
John
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on June 11, 2019, 09:09:41 PM
John, that's a wonderful video. Too bad he doesn't show details of that broaching device. Not that I have a mill or lathe sturdy enough to attach broaching machinery, but it would be interesting to see his take on it.

 
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on June 13, 2019, 12:19:54 AM
Here is the test setup for the transmission so far. Even if there are missing gears (third or fourth), I'll give it a shot, and continue testing:
(http://www.elisanet.fi/kz1706/test_for_test_setup.png)

The steel rod axle on the front will have cams for each brake. When turning the axle, there should then be a sequence, where one brake is locked at a time.

I have no idea, does that concept work, but as always, there is only one way to find out.

The brakes are to be held in position with screws, that are attached to the front 'post', or that's the plan anyway:
(http://www.elisanet.fi/kz1706/test_setup_drawing.png)

There are six brakes(one being 'neutral', as I found out) to fit in, and i'm sure the idle friction between the brakes makes it already quite tricky challenge. But then again, there are plenty of possible alternative options to test. 
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on June 16, 2019, 01:07:31 AM
Testing of the 0.6 mod transmission proved again at least one thing: multiple stages of gearsets multiply any, and all possible, even minor defects, which the printed parts have.

The result was (yet again) a grinding machine, with lots of friction and wobbling.

So far, what I have experienced with my entry level printer, it is highy unlikely to make such complex contraption just by printing the parts out and assemble them, and expect it to work smoothly.

The printed gears must be machined after printing, or formed by other means, to ensure better meshing.

One last thing, that came to my mind, is to 'roll' the printed gears, using the same module metal gear with some heat.

I don't have any 0.6 mod metal gears, so I'll have to skip the current version, and go back to the 1.0 mod one.

I have some mod 1.0 steel gears, that came with lathe. This one has 40 teeth, which I used to form the 12 teeth planet gear:
(http://www.elisanet.fi/kz1706/forming_with_mod_1_steel_gear.png)

The heat source:
(http://www.elisanet.fi/kz1706/heater.png)

Result after 'forming'. Left one is straight out from the printer, while one on the right is also printed, but post-formed:
(http://www.elisanet.fi/kz1706/printed_and_post_formed_gear.png)






Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on June 19, 2019, 11:45:06 PM
I'll have to give up with the current transmission, as there was similar problems with both the smaller and bigger version. Simply too many stages, and too many gear sets.

Next version will be Ravigneaux-based one, as it has far less parts, and uses only one ring gear.

At first I will be looking for the very basic version of it, to see, if I can figure out, how to attach required clutches and brakes to change the gears.

So far, the printed one is straight from the Youtube video: Y1zbE21Pzl0  
(http://www.elisanet.fi/kz1706/Ravigneaux_gearset.png)

It has gears, that have 45 degree helix angle. There is not any specific reason for doing that, other than to see, how they grind against each other, when compared to plain spur gears. There is some minor friction between the gears, but the main source for the friction is the tube, that is a part of small sun gear, which goes through the planet gear carrier's body. It took me a while to find that out.

Again an example, of how poorly the PLA-plastic parts slide against each other. So for the lubrication, I tried WD-40 and silicone spray. Neither worked. With graphite powder applied, the friction decreased, but only temporarily. Also, if the parts are tested with higher speeds, the surfaces, that face more friction, tend to swell. The planet gears on the above picture have 4mm holes in them, which I had to re-ream couple times, as they got sticky.       

Besides that, there is an extension for the Ravigneaux gear set, called Lepelletier planetary gear set. I find it even more interesting, than the Ravigneaux gear set itself, as it allows the gearbox to have more gears, by addind a single planetary gear set in front of it.

There are plenty of fancy logic charts and diagrams online about it, but how the actual working model of that could be accomplished, I'm not so sure about, as I'm not the brightest one, what comes to logic.

Instead, I'll go ahead and proceed with 'hands on' -procedure.

Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Admiral_dk on June 20, 2019, 09:26:46 PM
Your last picture looks like nice parts - so it is a shame that you still have trouble with too much friction  :-\

I hope that you will end up with a successful gear train before long ....

Best wishes

Per
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: ddmckee54 on June 20, 2019, 10:08:46 PM
I don't know how compatible it is with the PLA, but have you tried a lithium grease for lubrication?  The corrugations that you naturally get from printing the layers with an FDM 3D printer should work to your advantage as they'd tend to hold onto the grease.

It'll be interesting to see how the helical cut gears are going to hold up over time.  I would think that those same FDM layer corrugations will grind against each other as the gears rotate.  Maybe the gears will wear in or maybe they'll just wear out, only time and testing will give you that answer.

Don
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on June 22, 2019, 12:16:22 AM
Thanks for checking in, guys. The friction between certain printed parts is really a major issue. Perhaps not so much, if you plan on using the parts at very low speeds, like hand-cranked devices.

I like to machine all the mating surfaces(except gears, for now), so that there is a bit better chance to get them centered, or aligned with each other.

Although the mating machined surface(s) may seem smooth, they develop friction between each other, and therefore heat.

Not much heat is needed to make them gall, and the reaction, if allowed to continue, makes even more heat, to the point, where mating rotating parts, being of the same material, start to fuse together.

Then comes the question about lubrication. As mentioned before, I tried WD-40 and silicon spray, plus vegetable oil, vegetable glycerin, graphite powder, and even water and soap.

As far as I have tested, graphite powder, for some reason, gives the best results so far. That leads to conclusion, that perhaps the machined, smooth surfaces are actually porous. 

And if the machined surfaces are porous, the lubrications in fluid form would fill the pores, and stay there, allowing the mating surfaces to gall after all, without forming any constant film between surfaces.

But enough of that babbling. Here is the part with most friction(red through the orange part):
(http://www.elisanet.fi/kz1706/red_part.png)

At first, I smoothened the surface more with fine sandpaper. Then I used a glass rod to rub the graphite powder to it:
(http://www.elisanet.fi/kz1706/graphite_powder.png)

Result:
(http://www.elisanet.fi/kz1706/graphite_powder_applied.png)

Finally, here is the 'run-in' -setup. While motor is running, I hold the green part, which is the planet gear(s) carrier. 
(http://www.elisanet.fi/kz1706/run_in_setup.JPG)

By using the graphite powder as a lubrication between the red and orange parts, motor speed is up to 2000 rpm with no problem.

As Don mentioned, lithium grease could be a good one, as well as something like ptfe lube. I don't have those at the moment, but might consider buying them for testing.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: sorveltaja on July 24, 2019, 09:20:44 PM
An update: It's been quiet over a month now, but the project isn't forgotten. But still, unfortunately there comes time, when you have done a lot to make the 3D-printed thing(a model of an automatic transmission) to work smoothly, and finally, ran out of ideas.

Good thing is, that I have (hopefully) demonstrated most of the challenges, that one faces on project like this.

Bad thing is... no, there isn't anything bad in learning, after all.
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: Vixen on July 24, 2019, 10:11:18 PM
I have enjoyed making this journey with you, trying to help and encouraging you when I could.

Well done, You sure gave it a good run for it's money.

Cheers

Mike
Title: Re: Planetary gearbox - an attempt to make sense of how it works
Post by: ddmckee54 on July 24, 2019, 10:22:17 PM
sorveltaja:

Don't worry too much about "running out of ideas".  I've had projects sitting on the back burner for months before I got new inspiration of how to solve the problem.

When I built my wooden excavator models I worked on track link prototypes for over a year and went through I don't remember how many different designs before I got one that was buildable, reliable, and that I was mostly happy with.  I was only mostly happy with it because each track link had 7 individual parts and each model required 90 track links.

One of the models was a proof of concept model, much like your transmission is a proof of concept model.  I built 4 of the models for others and for various reasons 3 of the models were returned to me.  With 2 of the models the owners passed so the models were returned to me, and the 3rd owner downsized into a small condo and didn't have the room for a 1/16 sized excavator anymore.

Don