Custom 6 head CNC router "Help Needed"

G'day Guys, joined a few years back but have mainly lurked in the back ground. I am 3/4 the way through building a specialized 6 head CNC router to manufacture timber fishing lure bodies, the Machine has Y & Z but X is rotational (A) and revolves 6 chucks that hold the wood. This is my first dealings with rotational cnc so forgive my naivety (I do have a small normal cnc though). What I am trying to calculate is how to make the chucks (A) rotate 1:1 with the tool path created in Vectric Aspire wrapping. Currently the chucks do many many full revolutions while the tool path in Mach3 turns through one 360 cycle. I am guessing this isn't possible to achieve in setup and that a reduction gearbox of sort is needed? Is there a way without to much trial and error that I can calculate the reduction needed? My reduction from the pulley on the stepper motor to the chuck is 2.6:1, any help would be greatly appreciated, Regards Paul.

Never tried but would assume Mach3 auto tune feature could configure steps per degree as it does on a lateral axis, sounds to me as if configuration of mach3 is your problem not a gearbox, also is negative rotation enabled or does it only rotate one way in which case it must do what you say.

Your steps/unit are set wrong.

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Originally Posted by ger21

Your steps/unit are set wrong.

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Thanks for your replys. Yep! Managed to get G code and A axis (chucks) in step this arvo turning through 360 degrees, only problem is "Steps Per" is set at about 16.35, and I am maxing out speed wise at about 4-5 rpm (to slow) I think I am going to have to put a reduction gear box on it so I can up the rate of "steps per", unless there is something I am missing? Cheers Paul

A reduction would make it move slower. I think your issues are in the settings. What is the velocity set to?

What is your gearing now on the rotary axis?

Just 2.66:1 45mm pulley to a 120mm pulley on the chucks. I know most of the rotary tables I see seem to be about 60:1

Then you should easily be seeing a few hundred rpm.

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Originally Posted by ger21

Then you should easily be seeing a few hundred rpm.

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Do you mean in it's current format I should be able to achieve a few hundred RPM without the need of a gearbox? Cheers Paul.

You should what are your velocity and acceleration settings.

Shake & Bake,

Are you leaving out pertinent details such as motor size? The weight of six 5" or 6" inch chucks? How you are driving all six chucks (with one motor and a long belt or chain? A dedicated stepper driver for each motor? Please post a few images and more details.

Jeff...

Ok I see where I was going wrong, I was setting Vel and Acc for A similar to Y and Z, now I have set them way higher I am getting A to jog at a much faster rate and rotating the correct amount that I input (ie 360 = 1 revolution) steps per are set @ 15.54. When I run my G code my revolutions are too slow so I guess it needs further refining. Also on my normal flatbed CNC if I hold down the shift, the speed doubles, I am not getting that here, is there something in the settings I am missing? Thanks for your help too guys, cheers Paul.

You need to set the maximum feedrate in your g-code "F300" etc....
six (6) is the default feedrate for Mach3.

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Originally Posted by Shake & Bake

Ok I see where I was going wrong, I was setting Vel and Acc for A similar to Y and Z, now I have set them way higher I am getting A to jog at a much faster rate and rotating the correct amount that I input (ie 360 = 1 revolution) steps per are set @ 15.54. When I run my G code my revolutions are too slow so I guess it needs further refining. Also on my normal flatbed CNC if I hold down the shift, the speed doubles, I am not getting that here, is there something in the settings I am missing? Thanks for your help too guys, cheers Paul.

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I think the main thing your missing is the reading of the Mach3 documentation which would give you a better overall idea of how the whole thing should work, like any software there is a learning curve involved and by reading the manual you can often shorten this curve dramatically.

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Originally Posted by Louis_Cannell

I think the main thing your missing is the reading of the Mach3 documentation which would give you a better overall idea of how the whole thing should work, like any software there is a learning curve involved and by reading the manual you can often shorten this curve dramatically.

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Ah yes it a long held Aussie tradition to never use a manual, you are right of course, and I have down loaded a version now. Jalessi, Chucks are light weight Aluminium with Delrin jaws, very light I can turn the lot easily with one hand, driven by 1 Nema 34 1200oz stepper, the cuts are also very light, cutting with a thin small saw blade. Now to find a program that can generate continuous rotation, I can make a 360 G code with Vectric Aspire which will get me under way, but continuous rotation in one direction is my ultimate goal, my machine will work in a similar vein to this, to mass produce timber lure bodies cheers Paul.
"'''TURN YOUR SOUND DOWN"''' https://www.youtube.com/watch?v=6GkSPl2s_To

For producing toolpaths with continuous A axis rotation, you might look at DeskProto; it works off 3D meshes directly without having to roll a surface into a cylinder the way Aspire does. You can try it out for free for a month, and if you decide you like it, I sell it at a discount.

Cheers for that Andrew, I have downloaded a trial version, see how I go, will it work with stl.files? cheers Paul.

Yes, STL files are the preferred format, although it will also work with DXF and WRL meshes.

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Originally Posted by awerby

Yes, STL files are the preferred format, although it will also work with DXF and WRL meshes.

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I have downloaded the trial version and I have managed to create a continuous rotation, couple of small issues though? I have a slight jerky movement halfway through every revolution of A? It's not there when I jog, nor is it there in Vectric. Have you come across this? Also I have 1mm step over on the cutter, every revolution it stops and the carriage jogs forward 1mm is it possible to make it slowly spiral forward in a smooth movement? cheers Paul

This sounds like a Mach3 issue, probably due to your "roll-over" settings. From the Deskproto FAQ:


"7.4 - My part is damaged when rotation axis machining on a Mach3 driven machine.
It seems like some of the rotation axis toolpaths are incorrect, though on the DeskProto screen all looks fine. This problem may be caused by an optimization setting in Mach3.
Please check dialog "General Logic Configuration" of the Mach 3 Software. On this (huge) page you can find a section "Rotational" with two checkboxes, called "Rot 360 rollover" and "Ang Short Rot on G0".
If one of these options is checked this may be the cause of the error.
Here is what the Mach3 manual says about these two options:
Rot 360 rollover: if checked, it will measure a rotary axis modulo 360 (0 to 360 then restart at 0). Otherwise, it will keep counting up (for example, two revolutions would be 720).
Ang Short Rot on G0: if checked, it makes any rotary axis treat the position given as an angle modulo 360 degrees. Moves will be by the shortest route to that position. For example, if the axis were at 0 degrees and a request was made to rotate to 359 degrees, it would rotate -1 instead of +359.
The Rollover option introduces an extra movement to A=0 for every A-movement, which may destroy your part (and will take very long).
The Ang Short option needs to be unchecked as well: rotating via the shorter route may destroy your part, as DeskProto checked only the route that was prescribed."