Author Topic: Advanced 3D CAM and 3D machining  (Read 3647 times)

Online Jasonb

  • Full Member
  • *****
  • Posts: 9467
  • Surrey, UK
Re: Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #15 on: May 12, 2021, 07:20:54 AM »
I'd say 2D is horizontal and vertical surfaces only. 2.5D is when you increment down and run another horizontal and if that downwards increment means the tool needs to move sideways compared to the previous cut then that is how it copes with slopes doing them like contours on a map. The down side of this is if the shape is curved rather than just a straight angle then the horizontal stepover is less on near vertical surfaces and increases as they become flatter.

3D will follow the slopes and curves better and can adjust each "level" so that the step or scallop between cuts is constant no matter what part of a curve is being cut. Also instead of the the tool doing a horizontal path each time it can be constantly ramping down in effect following a spiral around the shape of the part. When the tool really starts to move about is when you have compound curves such as fillets where one curved surface meets another and then you see all 3 axis moving all over the place at the same time. For all of these you just select the overall shape or surface and the CAM will work out a single path, no need to string them together. Though you would usually do a roughing adaptive cut and then a finish or two selecting the best approach for each aspect of the part.

This is a short video I did at the weekend for someone who had only been using 2 and 2.5D and wanted some curves on some steel parts. Their first attempts produced a program that took 56mins on the simulator. This is the part being done in 7mins. (they had 16 to make) You can see on the adaptive how the 1mm vertical stepdown results in wider stepover as the curves flatten out towards the bottom. I then did a scallop on one side and a parallel finish on the other. Though in the end orientating the work vertically would have given the better surface finish.

<a href="https://www.youtube.com/watch?v=cj7lD1hIJro" target="_blank">http://www.youtube.com/watch?v=cj7lD1hIJro</a>

Offline fumopuc

  • Full Member
  • *****
  • Posts: 3231
  • Munich, Germany, EU
Re: Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #16 on: May 12, 2021, 08:02:36 AM »
For a non-cnc guy, what is '2.5D'?   :headscratch:


Hi Chris. a lot of wise explanation is given already. I like this forum for that very much.
Your closest example for 2.5 D should be your new toy, the so called "3D" printer.
In reality it is working in 2.5 D only.
Creating the part in x and y by small layers.
What Jason has shown, the "parallel" machining, specially the finishing of the second side of the part, is something what the hobby "3D" printers are not able to do.
But that is what I do understand by 3D machining.
« Last Edit: May 12, 2021, 08:31:08 AM by fumopuc »
Kind Regards
Achim

Online Jasonb

  • Full Member
  • *****
  • Posts: 9467
  • Surrey, UK
Re: Advanced 3D CAM and 3D machining
« Reply #17 on: May 12, 2021, 10:21:34 AM »
I'd actually say the scallop on the front side is far more £d than the parallel on the back.

On the parallel the work "puts on a cut" in the X direction (the 0.5) and cuts using Y & Z (the 2.0D) giving the total 2.5D, if you watch the DRO readout at the end you can see X only moves in steps between cuts.

On the Scallop the tool is constantly moving in all three planes so true 3D.

J

PS Jo thanks for moving things I was actually thinking of PMing Mike and asking if he wanted me to move my earlier reply to a new thread rather than hijack the build.

Offline john mills

  • Full Member
  • ****
  • Posts: 417
Re: Advanced 3D CAM and 3D machining
« Reply #18 on: May 12, 2021, 10:23:44 AM »
when i was programming cnc machines i did not have cad cam programs and the computer programs worn't
powfull enough to do much.one of the machines i wrote programs for   ( a mazak v5 ) was only 2.5d
you could only put 2 axis on the one line and not y and z so it was limited to just x and y  but could do x and z so for one job to profile a curved groove the job had to be turned at 90 degrees so i could use and x  g 18 programming using g codes.programing the mazak v10 was able to do 3d as it would do 3 axis at once so i programmed 3d shapes but used subroutine and repeat lines a number of times to produce shapes .often with a
63mmdia facing cutter manually worked out the figures and tool radius compensation to produce the right shape.
mostly machining hot tool steals or some times   high tensile  steels .the cad cam  program that came latter
was not able to sort out the 2 axis on one line for the mazak v5 but i was no longer needed and was retrenched
they would have found out when i was gone.they did not want to know when i told them i had just continued until i left.they would have found out when some one else tried  .the people left  had done little programming and would have had a lot of learning to do  .the cad and the cam programs you have now seam to be able to do these ships on your machines.as i programmed the muzak v 10 the last row of cuts on jasonb video shapes could have been done with the lines to produce the shape an incremental shift  then repeat the number of times required 
John     
« Last Edit: May 12, 2021, 10:30:39 AM by john mills »

Online Vixen

  • Full Member
  • *****
  • Posts: 3076
  • Hampshire UK
Re: Advanced 3D CAM and 3D machining
« Reply #19 on: May 12, 2021, 10:26:21 AM »
This is getting a bit mixed up. Let me try to clarify things.

I do all my CAD work in 2D, plan view, side view, front view etc. I do not do 3D drawings

My two CAM programs DesCAM (no longer on sale) and EstleCAM are also 2D/2.5D, neither of these programs can do 3D CAM

I create a pseudo 3D surface from a large stack of 2D contours at different heights.(like the contours on a map or the steps on a 3D printer) Each layer (contour) is laboriously created in the 2D drawing package, then made into g-code by the 2D CAM software. This is crude stuff, very slow and time consuming but it does make an interesting intellectual challenge for me. The tool path I showed earlier took several days to prepare, but that was OK by me while I was isolating and confined to barracks. I was not going anywhere.

True 3D modeling and 3D CAM requires much more advanced software and processing power than I have available.  3D CADCAM is intended for the industrial setting. Solidworks, Dasault, AutoDesk are some of the big players and they all require thousands of dollers, pounds or euros each year for the privilege of using there products. All the processing is done their end over the net, the user only has a terminal. Everything is done of the internet, so you need a good reliable connection and bandwidth

However AutoDesk have taken the decision to release some of the Fusion 360 CAD CAM free for the use of students and hobbyists. They see this as an investment for the future, as they expect many of the students to eventually become paying users.

I do not know of anything useful between my crude 2.5D CAD CAM and the high end 3D CAD CAM. That would be a very useful area to explore.

If I were to buy a new hi-spec PC, If I were to go over to Win10 along with all the problems associated with Microsoft control of Win10; I could download Fusion 360 and eventually learn to become a Fusion 360 user like Jason. I cannot see that happening in the near future

Mike
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline tangler

  • Full Member
  • ****
  • Posts: 834
  • Christchurch, UK
Re: Advanced 3D CAM and 3D machining
« Reply #20 on: May 12, 2021, 10:40:52 AM »
Guys,

My take on 2.5D is slightly different.  The point being that the CAM program takes it's input from a 2D drawing which controls the X and Y movements but the Z movement is a single depth specified by the user.  This system still gives a fair amount of versatility.  Take the example of a simple circle.  The program has been told the diameter of the tool being used.  The options are then to cut around the outside of the circle or the inside of the circle or for the centre line of the cutter to follow the circle.  Additionaly, the program can be instructed to clear inside the circle or outside the circle and can do this with control over the depth of cut for each pass.  The program can follow any continuous single line according to the parameters mentioned above.  Anyhow, that's how the cam system that came with my Denford mill worked.

Cheers,
Rod

Online Jasonb

  • Full Member
  • *****
  • Posts: 9467
  • Surrey, UK
Re: Advanced 3D CAM and 3D machining
« Reply #21 on: May 12, 2021, 01:30:16 PM »
So Mike, coming back to the "peeling" that got us started do you produce a drawing for the pocket at 6mm deep and then let your CAM workout the path it will take to peel that away. Then do it again for 12mm deep and so on finally combining them all into one long g-code?

If so then that is as you say a long job and also leaves 6mm steps at the edge. With a more upmarket CAM such as F360 all the user has to do is click on the geometry which in this instance could be anywhere along the inner edge of the bolting flange and then just specify a max depth of cut, stepover, feedrate and also a minimum stepdown. The CAM will then work out where the boundry is for each 6mm layer if 6mm is set for max DOC and also once everything has been removed at that level go around the sides again stepping the edge to say 1mm increments leaving less to come off with the finishing passes. It will then do the same again for each multiple of 6mm until the bottom is reached. Note it's usual to specify an amount of stock to be left such as 0.5mm radial and 0.5mm axial which will be removed by the finish strategy.

So much less manual working out involved and it also knows what the roughing passes have left so only does the finish passes to remove the remaining material.

Offline kvom

  • Full Member
  • *****
  • Posts: 2649
Re: Advanced 3D CAM and 3D machining
« Reply #22 on: May 12, 2021, 01:57:43 PM »
While many 2.5D tool paths just repeat at increasing values of Z, there are some that have coordinated Z motion.  The most common of these are ramped profiles where each G1 command has 3 coordinate values.  There are also helical moves for machining holes and milling threads.

I have been a CamBam user for over a decade, but have done only a couple of 3D toolpaths.  In the past I would take paper plans and draw them in CAD to produce DXF files.  Since I now get SolidWorks free as a veteran, I'll model parts there in 3D, and then export to DXF.  My last two builds I received the "plans" as SW models for all the parts, thus saving a lot of work.

Once I load a DXF file into CamBam, I can manipulate it as needed before applying various operations to selected lines within the drawing.

For the type of pocketing Mike used, CB has an operation called Trochoidal Pocket.  Trochoidal is just a technical term that means the tool's angle of contact with the work is kept constant.  Constant angle means feedrate can be constant as well.  The toolpath for a pocket starts with a straight plunge to target depth followed by an outward spiral.  The position of the spiral is calculated to maximize the size of the spiral within the pocket shape.  The rest of the pocket is completed by successive arcs.  There is an option to machine each alternate arc in reverse direction, but I prefer to just have the tool return rapidly to the next arc allowing any chips to clear the tool.

After this operation, the sides of the pocket will have some scalloping that I remove with a subsequent profile operation.  I specify a roughing clearance of a few thou on the pocketing.

CamBam has a trochoidal profile op as well, and I have used this to machine slots using a tool whose diameter is smaller than the slot.  The advantage in aluminum is that chip welding is eliminated.  I can also cut the slot at full depth.


Offline Hugh Currin

  • Full Member
  • ****
  • Posts: 720
  • Box Elder, SD, USA
    • www.currin.us
Re: Advanced 3D CAM and 3D machining
« Reply #23 on: May 12, 2021, 06:04:16 PM »
Mike: My hat is off to you for the skill and patience to generate tool paths as you do. You're results speak for themselves. If I tried this I'd be tracking down errors for the foreseeable future. Nice job.

kvom: I think I'm about where you are. I use VariCAD to generate 2D *.DXF files and import these to CamBam. I've poked at the 3D features in CamBam but not cut parts with them. I've found I can import 3D *.STL files into CamBam. My older version of CamBam doesn't have the trochoidal generator you mention, but I see it's available as a plug-in. I'll have to get that or upgrade.

I'm trying to get Fusion 360 going for their milling and lathe CAM. Also, the parametric modeling would be helpful in design (once it's learned). I need to pick a project with some 3D (far simpler than Mike's) that would force me to do some 3D milling. But way to many projects already.

Thanks.
Hugh

Online Vixen

  • Full Member
  • *****
  • Posts: 3076
  • Hampshire UK
Re: Advanced 3D CAM and 3D machining
« Reply #24 on: May 12, 2021, 06:43:30 PM »
Hello Hugh

Thanks you for that comment. It is always nicer when people appreciate how much effort you have taken, much nicer than receiving flak for not using the latest and greatest.

Incidentally, the 'peel' pocketing of EstleCAM is trochoidal milling. 'Peel' was a shorter word to put on the function select button. You can trochoidal mill a pocket or trochoidal mill an inside or outside profile. There are also options to rectangular milling or to raster mill out pockets. I actually like the term 'Peel' to me it conjures up images of a pencil sharpener peeling off a thin shave of wood.

Mike
« Last Edit: May 12, 2021, 06:47:11 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline fumopuc

  • Full Member
  • *****
  • Posts: 3231
  • Munich, Germany, EU
Re: Advanced 3D CAM and 3D machining
« Reply #25 on: May 12, 2021, 06:50:32 PM »
I'd actually say the scallop on the front side is far more £d than the parallel on the back.

On the parallel the work "puts on a cut" in the X direction (the 0.5) and cuts using Y & Z (the 2.0D) giving the total 2.5D, if you watch the DRO readout at the end you can see X only moves in steps between cuts.

On the Scallop the tool is constantly moving in all three planes so true 3D.

J

PS Jo thanks for moving things I was actually thinking of PMing Mike and asking if he wanted me to move my earlier reply to a new thread rather than hijack the build.


Hi Jason, you are right. I have been focused so much to the continuous up and down movement of the Z axis that I missed the only step by step movement of the x axis here.
As you mentioned already, the scallop movement at the other side is a much better example for 3D machining/movement. 
« Last Edit: May 12, 2021, 08:14:15 PM by fumopuc »
Kind Regards
Achim

Online Jasonb

  • Full Member
  • *****
  • Posts: 9467
  • Surrey, UK
Re: Advanced 3D CAM and 3D machining
« Reply #26 on: May 12, 2021, 07:33:01 PM »
Maybe I was confused by the title of "Advanced 3D CAM..............." and thought that it was a place to discuss 3D CAM :headscratch:

Hugh it would certainly be worth trying to get F360 to work on your machine, as you say it's not just it's CAM capabilities but the whole design aspect and having all these integrated into one place so you can easily jump back and forth from one thing to another. It's one feature I miss by using Alibre for my drawings and F360 for the CAM as if there is a major change I want to make to a part I Have to do it in alibre and import a new STL file and start the CAM again, with it all under one Make you can alter a feature and when you click back on Manufacture ( the CAM part) the cutting paths will update with a click of the mouse. I do use Fusion to make small changes and infact there are some things it handles better than Alibre.

It's also possible to use Alibre offline so you can do your CAM when you are traveling about with poor or expensive connection options. Not sure what the system requirements would be on a Linux machine but I don't use anything particularly advances on my Windows PC and only get the odd time it slows F360 down a bit.

Achim happy to clear things up and good to know some take my comments constructively in the way they are meant.

Online Vixen

  • Full Member
  • *****
  • Posts: 3076
  • Hampshire UK
Re: Advanced 3D CAM and 3D machining
« Reply #27 on: May 12, 2021, 08:09:24 PM »
Maybe I was confused by the title of "Advanced 3D CAM..............." and thought that it was a place to discuss 3D CAM :headscratch:

Jason, your considered contributions will always be welcome. You have more experience with Fusion 360 than any of us. Hopefully the new topic will enable all of us to advance our knowledge of whats available and what it can or cannot do.

Mike
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Online Vixen

  • Full Member
  • *****
  • Posts: 3076
  • Hampshire UK
Re: Advanced 3D CAM and 3D machining
« Reply #28 on: May 14, 2021, 10:35:08 PM »
Quote
Mike:
Back in Post #338 you showed a screen shot of the dry sump that showed the depth of cut for each layer.  How did you generate those lines?  I've got my suspicions, but "Enquiring minds want to know".
Don

Don, Jason,

It's funny the way things change with time. I have been building engines, tanks and a lot more in my CNC workshop for nearly 25 years. During that time, I have often taken flack from other model engineers, who say what I am doing is not 'real' model engineering. That's because I am not using the traditional Myford lathe or whatever. Besides CNC is realy cheating; it's too easy, there's no skill, there's nothing to it. You press the button and out pops a completed engine.

Now suddenly, I'm receiving incoming from a totally different direction. I'm now being  told:  "Holy Moly" your doing it all wrong. That's definitely a long winded way to do it and how much BS you're willing to put up with? What you should be doing is pressing a button in Fusion 360. The 3D CAD/CAM will work it all out for you and do in minutes what can take you several days to do. The same model engineers, I mentioned earlier, may now rightly say "it's too easy, there's nothing to it. You press the button on Fusion and out pops a completed engine." Where is the skill in pressing that button?

As I have said before: I have 2D CAD and some 2D/2.5D CAM. I have no 3D stuff. I come from an old school which tought me "use what I have available and make what I dont have."  I am happy to apply that philosophy to my engine building. It may be slow, it may be long winded but it gives me immense pleasure and the results speak for themselves.

As to how I generate those lines? I use 2D CAD. You know: plan view, side view, end view. and the occasional cross section. For my pseudo 3D work I simple create (by old fashioned drafting) a number of cross sections at about 0.25 mm (10 thou) spacing and even closer spacing where rate of curvature is greater. These cross section contours are transferred as individual DFX files to my 2.5 D CAM which does the tool path G-code conversion.  I combine all the G-code(s) into one big file. OK it's slow, it's long winded, it's old fashioned, it's probably the way Noah built his Arc. But it works well enough for me. I'm in no rush,  I'm not going anywhere for a while yet.

Dont get me wrong, I have nothing against 3D CAD CAM. I would dearly like to use it if I get the opportunity. Maybe someone would sponsor me and provide a nice new computer, Maybe someone will assure me that MS will not mess about with Win 10 while I am using it. And most importantly; Maybe someone will assure me that Autodesk will not suddenly change 'free' Fusion 360 into FEE Fusion, when they think they have hooked enough users.


Now lets cool thing down and enjoy our Model Engine Making

Cheers   :cheers:

Mike

« Last Edit: May 16, 2021, 12:39:05 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Admiral_dk

  • Full Member
  • *****
  • Posts: 3752
  • Søften - Denmark
Re: Advanced 3D CAM and 3D machining
« Reply #29 on: May 14, 2021, 10:41:26 PM »
I'm sorry if it sounded as I has anything against your methods Mike - I just know how many errors that usually creeps in the .nc (G-Code) files when I edit them manually -> I'm very impressed with your results.

Per

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal