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Using Y axis for a Rotary table ?
« on: October 24, 2019, 10:41:57 PM »

I have built a small prototype CNC engraving machine. It will be engraving the face of small brass and silver discs using cutters much like lathe cutting tools ( ie, non-rotating). It uses the X and Z axes in their normal fashion but not Y. My third axis is a rotary table configured as the A axis. Jogging the various axes around works just fine.

My CAM program is Sheetcam which does 2.5D G-code. (The engraving is 2.5D cutting so I really don't want to complicate things by using 3D CAD or CAM.) Sheetcam will not produce G-code for an A axis and you cannot configure Mach 3 with Y as a rotary axis - only A,B, or C. At least, not without some sort of work around.

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 ?
David Morrow

Offline BR549

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Re: Using Y axis for a Rotary table ?
« Reply #1 on: October 25, 2019, 10:41:30 AM »
Show us a picture of what you are doing. There is always a way . It could be as simple as just using the rotary as the Y axis. In sheet cam you would limit the size of the drawing in Y axis to the size of the circumference of the disc. Then simply cam it as XYZ and run it as XYZ.

(;-) TP

Re: Using Y axis for a Rotary table ?
« Reply #2 on: October 25, 2019, 12:57:52 PM »
I have tried making the rotary table the Y axis but my suspicion proved out that it would not work. For example, assume that you are cutting a circle and the cutter starts at the 9:00 o'clock position and runs clockwise around. The cutter move up the Y axis until it reaches 12:00. But then the Y axis reverses as it heads towards 3:00 o'clock. With a rotary table, the chuck needs to continue its rotation.
David Morrow

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Re: Using Y axis for a Rotary table ?
« Reply #3 on: October 25, 2019, 07:05:59 PM »
I don't follow you. I have done this many times over the years teh rotary can rotate 360 degs amd follow teh Y toolpathing as it is only as big of an area as teh circumference of teh part. The rotary can move both directions. I have even used sheetcam to makes xy cuts on a rotary with plasma cutting.

Unless there is something I am missing on your project. Do you have a picture of a part ?

(;-) TP
Re: Using Y axis for a Rotary table ?
« Reply #4 on: October 25, 2019, 07:09:03 PM »
Much of the issue is that I am cutting with a lathe type cutting tool and that only cuts on the one side. If the rotary table reverses, it will rub on the non-cutting side.
David Morrow
Re: Using Y axis for a Rotary table ?
« Reply #5 on: October 25, 2019, 11:03:31 PM »
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.






« Last Edit: October 25, 2019, 11:09:28 PM by David Morrow »
David Morrow

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Re: Using Y axis for a Rotary table ?
« Reply #6 on: October 26, 2019, 08:01:46 PM »
V shaped lathe tools cut both directions (;-) This looks more like a TURN application rather than a Mill function.

IF you are engraving have you thought of using drag type engraving bits ?

Do you have a picture of what the finished part looks like ?

Just a thought , (;-) TP
« Last Edit: October 26, 2019, 08:04:02 PM by BR549 »
Re: Using Y axis for a Rotary table ?
« Reply #7 on: October 26, 2019, 08:23:28 PM »
Here's an example that I found online :


« Last Edit: October 26, 2019, 08:26:55 PM by David Morrow »
David Morrow
Re: Using Y axis for a Rotary table ?
« Reply #8 on: October 26, 2019, 08:58:22 PM »
Here is a manually operated machine that does what I am trying to do with CNC :

https://www.youtube.com/watch?time_continue=39&v=ynHtaqsvODs
David Morrow

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Re: Using Y axis for a Rotary table ?
« Reply #9 on: October 26, 2019, 09:30:41 PM »
OK a ROSE ENGINE. Those are complicated hammer knockers.  It can be done several ways with CNC using XYZ and C as teh rotary for rotation of teh Cutter bit basically as drag engraving and doing it with tangent cutting with teh spindle itself rotating to follow teh bit travel direction. Mach3 can do it.

As rotary engraving it is a simple process for teh machine but not so easy CAM wise to genreate teh Gcode.

(;-) TP