Rotary Table use with Sheetcam and Mach 3

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David Morrow
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Rotary Table use with Sheetcam and Mach 3

Post by David Morrow » Fri Oct 25, 2019 2:03 am

I've been using both Sheetcam and Mach 3 for 15 or more years so I'm reasonably familiar with them both but I have created a bit of a situation for myself. This may be a bit hard to describe.

I have built a small prototype CNC engraving machine. It will be engraving the face of small brass and silver sheet using cutters much like lathe cutting tools ( ie, non-rotating). It uses the X and Z axes but not Y. My third axis is a rotary table. My machine controller is Mach 3 and you cannot configure Y as a rotary axis - only A,B, or C.

So, now I have drawings that I import into Sheetcam and create my G code as usual but Sheetcam does not recognize the A axis.

This is a real puzzle and I'm not sure where to turn. I would prefer to stay with both Sheetcam and Mach 3 but I'm beginning to think that this will not work. Any thoughts ?

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Les Newell
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Re: Rotary Table use with Sheetcam and Mach 3

Post by Les Newell » Fri Oct 25, 2019 10:46 am

Is the rotary axis a rotating chuck or is it using rollers that drive the outside of the part?

David Morrow
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Re: Rotary Table use with Sheetcam and Mach 3

Post by David Morrow » Fri Oct 25, 2019 2:28 pm

It’s a rotating chuck.

David Morrow
Posts: 14
Joined: Sat Nov 21, 2015 7:53 pm
Location: Vancouver, BC

Re: Rotary Table use with Sheetcam and Mach 3

Post by David Morrow » Sat Oct 26, 2019 3:15 am

Here are a couple of photo's. Remember, this is just a mockup but a mockup that works well enough to test parts placement and, of course, software compatibility. Once I get it to work, I will re-make everything out of aluminum and brass along with some proper bearings and timing belts. Also, it is sitting on one of my CNC routers so some of what you see in the background is another machine.

It looks like I can't embed the photo's so here are links to a couple :

http://www.ldrider.ca/webphotos/rose-engine-3054.JPG

http://www.ldrider.ca/webphotos/rose-engine-3055.JPG

This is a manual, and much more complex version :
https://www.youtube.com/watch?time_cont ... nHtaqsvODs

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Les Newell
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Re: Rotary Table use with Sheetcam and Mach 3

Post by Les Newell » Mon Oct 28, 2019 2:32 pm

Sorry for the delay in getting back to you. The weekend got in the way.

First of all, don't worry too much about defining an axis as rotary in Mach3. In my experience that causes more problems that it solves. With rotary axes Mach 'wraps over' coordinates when it reaches a full rotation and this causes all sorts of issues if you aren't expecting them. For instance if you use G0 A350 then G0 A10, it will move +20 degrees rather than -340 as you may expect. I generally recommend that rotary axes are defined as linear. In your case you could use the Y axis as the rotary axis. Just set up the axis so 360 units is one full rotation.

Basically you need the post to convert X,Y cartesian coordinates to radius + angle polar coordinates. Feed rates get a bit weird when you do this and the math can fall over in ugly ways when you cross the centre of rotation. I don't have a polar post processor but I could have a go at writing one.

Vmax549
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Re: Rotary Table use with Sheetcam and Mach 3

Post by Vmax549 » Tue Oct 29, 2019 6:15 pm

Hi LES , If it helps it appears he is building a CNC ROSE ENGINE.

Just a thought, (;-) TP

David Morrow
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Re: Rotary Table use with Sheetcam and Mach 3

Post by David Morrow » Wed Oct 30, 2019 2:26 am

Yes it is a Rose Engine

Making the rotary table the Y axis doesn't work. As a test, I drew a simple 2.00" diameter circle and had SC start the cut at X= -1.00, Y = 0.00 As the routine started, the X axis gradually moved towards 0.00 and then over to +1.00. Exactly as it would if everything was linear. I can't have that because of the single sided lathe tool cutter. In my perfect world, the X axis would stay put at -1.00 as the rotary table Y axis turned one complete revolution. The Y axis also moved although I need to get the steps calculation corrected. That also means that I could not make the rotary table the X axis. One of them has to stay put in this test.

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Les Newell
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Re: Rotary Table use with Sheetcam and Mach 3

Post by Les Newell » Wed Oct 30, 2019 11:47 am

Hmm, I now understand what you want to do. I'm afraid SheetCam won't be able to help you for this. I don't know of any cam packages that will do it.

David Morrow
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Re: Rotary Table use with Sheetcam and Mach 3

Post by David Morrow » Wed Oct 30, 2019 5:54 pm

Thanks Les, I kind of figured that was the direction this was heading.

Vmax549
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Re: Rotary Table use with Sheetcam and Mach 3

Post by Vmax549 » Thu Oct 31, 2019 5:26 pm

David over on teh Mach website I gave a LINK to a site that offers free coding software to do CNC rose engine work.

Just a thought (;-) TP

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