Author Topic: Going over to the dark (CNC) side!  (Read 10376 times)

Online Jasonb

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Re: Going over to the dark (CNC) side!
« Reply #30 on: March 03, 2019, 01:40:46 PM »
Jo,

 I based my comment on this one of yours, my bold

Quote
I can see lots of uses for one but its like 3D printers if it takes hours and hours to do the printing/machining  :Doh:

Kvom,

 I actually cut from a larger piece of material and if you look at the simulation there are some tabs around the outside. I'm happy to leave tabs as the parts had all the corners knocked off after machining to make them look more like castings and less like cut from barstock.


I've not looked for nesting but will do so and can see it would be good if you had several parts, for now just moving the flat bar along in the vice is OK.

Mike (Vixen)

I ran a test in the UPVC and it cut in that time though could have been a lot faster. After doing that I thought I would play safe as it's early days and reduced DOC to 1mm but did up the speed to 3000rpm and added an extra tab. This added about 3mins to the job according to Cut2D.

I'd be interested to know what sort of time you would expect it to take from your machine or anybody else for that matter, let me know if you want the part file. I'm just using a 6mm FC-3 cutter for now and could go faster if I changed to an aluminium specific cutter, also don't have any chip clearance or lubrication sorted yet so need time to keep up with that manually.

Murray,

Good to see you chipping in here, would definately be interested in how long this would take you as having seen your machine in action it can shift metal at a fair old lick :o

Yes I remember the posts about the alternative driver over on ME but will stick with this setup for a while until I find out what I want out of the machine.



So this is the test piece done in the 8mins for the main side, you can see the tabs around the edge but it has not cut through as its thicker than the metal part.



Now when I loaded up the revised code for the metal version I noticed that there was an extra path showing on the screen. Should really have stopped there and sorted it out but decided to just keep the mouse over the stop button.



At least I have learn one thing today as with about 30secs left to run I got one of the unique features that Jo mentioned but stopped it soon enough so I need to trust whats on the screen



I did not video all the cutting but have stitched 3 clips together which show approx the first cut of each of the three paths, think I could also speed up the ramping which would reduce overall time a bit.






Online steamer

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Re: Going over to the dark (CNC) side!
« Reply #31 on: March 03, 2019, 02:05:32 PM »
Yup    cnc tends to be pricey..    Yup it takes a while to climb the learning curve hill.   What isnt being mentioned is the set up time saved.   The tooling saved.

Think about those curves.   On the manual, theyre a RT job and a break down and set up cycle.   Everytime you break it down and set back up is time and loss  of accuracy.   You need to spend money ona rotary table and the furniture it takes to use it.    You need to schelp it on and off the mill, and you need to store it.  With CNC...you need an endmill Nd one set up.    Used right, cnc rocks!
Dave
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Online b.lindsey

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Re: Going over to the dark (CNC) side!
« Reply #32 on: March 03, 2019, 03:49:53 PM »
Dave, remind me which tormach you have at work?

Bill

Online Jasonb

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Re: Going over to the dark (CNC) side!
« Reply #33 on: March 03, 2019, 04:26:49 PM »
Apart from the fact that I used a scrap bit of 6mm aluminium that had a hole just in the wrong place this is it with all the machining done from the front. Just under 12mins from pressing run to completion.



I'm sure it could be run faster, at least that is what Ketan is telling me but then again I don't think he knows machines can be run slower than 5000rpm  :ThumbsUp: Also he and the late JS used these these machines to make parts to sell so they don't want to be wasting time.

I'm sure JS has a chuckle in his grave when people say they prefer British Made tools, what would they say if they knew he was banging them out on a similar machine to mine along with all those extras for Myfords :LittleDevil:


Online crueby

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Re: Going over to the dark (CNC) side!
« Reply #34 on: March 03, 2019, 04:28:45 PM »
Much satisfaction to be had from cranking the mill with your own paws,  but there is!      Hmmmm!!

Online steamer

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Re: Going over to the dark (CNC) side!
« Reply #35 on: March 03, 2019, 04:29:42 PM »
Dave, remind me which tormach you have at work?

Bill
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Online b.lindsey

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Re: Going over to the dark (CNC) side!
« Reply #36 on: March 03, 2019, 05:02:20 PM »
Ok thanks.

Bill

Offline Woodguy

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Re: Going over to the dark (CNC) side!
« Reply #37 on: March 03, 2019, 05:10:58 PM »
I converted my SX-3 to CNC and have used it quite a lot. The problem with it though is that is has a maximum spindle speed of 1800 rpm. Since many of the parts I wanted to make were small, and needed small cutters, the machine required extremely slow feed rates. A good feeds and speeds calculator like GWizard is very helpful in keeping cutters in one piece.  Using the biggest cutter that would do the job was essential.


Fusion 360's cam really works well and the adaptive clearance toolpath is particularly useful.


I solved my spindle speed problem by shifting those parts to my CNC router with a 24K rpm spindle.

Online Jasonb

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Re: Going over to the dark (CNC) side!
« Reply #38 on: March 03, 2019, 05:19:37 PM »
Yup    cnc tends to be pricey..    Yup it takes a while to climb the learning curve hill.   What isnt being mentioned is the set up time saved.   The tooling saved.

............................................

Quite so Dave, I needed two plates machining to mount the parts onto with a different ctr point on each and each part needed to be mounted and removed six times. Not to mention the constant worry of winding a handle too far!

Offline jadge

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Re: Going over to the dark side!
« Reply #39 on: March 03, 2019, 08:17:16 PM »
I now run PathPilot;  here a card from Mesa generates the pulsing, and it's much smoother.  I've set rapids to 150, although I could have gone faster.  The screen layout is a lot better too.  The main disadvantage of PathPilot is that one can't jog the axes during a tool change, which is possible with Mach3.

Yes, that's a bit of a pain. I used to manually add a G00 Z move to the program just before each toolchange. But I kept forgetting, so I've now set a reference point on the machine and I've tweaked the post-processor to include a G30 command as part of the toolchange sequence.

Another issue with PathPilot is that being a US program the metric side is a bit cavalier. A maximum jog increment of 10mm is likely to require an underwear change if you're not expecting it! Although I design in both metric and imperial I run the CNC mill solely in metric, mostly with metric cutters.

Andrew

Offline jadge

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Re: Going over to the dark (CNC) side!
« Reply #40 on: March 03, 2019, 08:51:35 PM »
A few more random thoughts:

A CNC mill and 3D printer are not the same. One is a subtractive process and other is an additive process. The way parts are designed for each machine is different. Something that is easy on a CNC mill may be difficult on a 3D printer and vice versa. The 3D printer is certainly the slowest, as one is limited by the fixed nozzle diameter and limit range of height steps. Whereas for a CNC mill you can just use a bigger cutter, within the power limits of the machine. A useful feature of the more complex CAM programs is re-machining. As an example take the nameplate made by JasonB. To decrease cutting time you could rough out the shape using a large cutter. And then remachine with a smaller cutter to finish off the small internal radii. The CAM program knows where the larger cutter has been, so the smaller cutter only mills out the features it needs to.

My CNC machining times have ranged from less than a minute to over 6 hours. But of course you can go and do something else, like make tea or cut the lawn while it's running. Same for a 3D printer, I sometimes leave mine running overnight.

I'd have tackled the engine pillars in a slightly different way. I'd have done a helix all the way through in the centre and then incremented out, leaving about 0.5mm of stock. Then I'd have done a profile pass full depth to finish using a circular approach and retract. That way you avoid possible tool marks from multiple passes, and minimise tool deflection. I'd then take out the recess in one pass. For the outer profile I'd probably do it in two depth passes, again leaving about 0.5mm stock. Followed by a full depth profiling pass. I'd probably leave the tabs, but experience shows they're a PITA to remove without impairing the visual appearance of the part. At least I'd try and put them in places that mate with other parts so they're not seen.

Using a CNC mill has changed the way I design parts and assemblies, and has also changed the way I machine, some of which has fed it's way back to the way I use the Bridgeport mill.

There are several uses for the CNC mill in my workshop:

To make repetitive parts, like traction engine wheel spokes that would be a pain to do manually

To make parts that could be done manually but would be time consuming to set up - like radii and fancy profiles

To make parts that are impossible on my manual machines like special cutters and true bevel gears

To save time and avoid foul ups when making parts commercially

Andrew

Offline kvom

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Re: Going over to the dark (CNC) side!
« Reply #41 on: March 03, 2019, 11:55:16 PM »
My PathPilot screen has 1mm as the maximum jog.  I also set jog feed rate to 40% of rapid.

Online steamer

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Re: Going over to the dark (CNC) side!
« Reply #42 on: March 04, 2019, 12:54:29 AM »
My PathPilot screen has 1mm as the maximum jog.  I also set jog feed rate to 40% of rapid.

Ditto
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Online Jo

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Re: Going over to the dark (CNC) side!
« Reply #43 on: March 04, 2019, 07:31:36 AM »
Using a CNC mill has changed the way I design parts and assemblies, and has also changed the way I machine, some of which has fed it's way back to the way I use the Bridgeport mill. There are several uses for the CNC mill in my workshop:

To make repetitive parts, like traction engine wheel spokes that would be a pain to do manually

To make parts that could be done manually but would be time consuming to set up - like radii and fancy profiles

To make parts that are impossible on my manual machines like special cutters and true bevel gears

To save time and avoid foul ups when making parts commercially

Thanks Andrew, all of those confirm my thoughts of having CNC at home.

Short term I am delaying acquiring CNC as it is too much like what I used to do at work and I am trying to forget that horrible time of my life  :ShakeHead: Longer term with the likes of Honda pulling out of the UK I suspect there are going to be a number of machine tool acquisition opportunities to be had over the next two years and I can see CNC being in the mix of tools that become available so it could be something to spend some spare cash on invest in  :-X The far easterner tool manufacturers, once you get above their built down to a price DIY machines, do a reasonable compact CNC - the one Jason was given was one I was looking at but I couldn't justify the cost  :hellno: .

As for uses of a CNC ... I do have a number of engines with multiple items - there are a few traction engine spokes to make :) but the items that are really going to be multiples are my big rotary/radial builds - the Anzanis, the Bentley and the Gnomes. I am not sure if the straight 4 engines would benefit from CNC as much  :noidea:


One of the advantages of being retired is you have plenty of time  :headscratch:

Jo

 
 
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Offline jadge

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Re: Going over to the dark (CNC) side!
« Reply #44 on: March 04, 2019, 09:22:31 AM »
My PathPilot screen has 1mm as the maximum jog.  I also set jog feed rate to 40% of rapid.

That's useful to know. I contacted Tormach about the issue and they promised to change the values. I'm still using an early version of PathPilot, so it may be that Tormach did indeed update the values in a later release.

Andrew