[Jim Dawson]

Makes sense, should work nicely since you have that encoder feedback directly on spindle. I guess it does make sense for you to stay 1 to 1 so you have plenty of pulley grip. Here's another interesting thing I just found out about the dmm drive, the 500khz frequency limit was apparently just a "conservative" spec. The engineer informed me that the dyn4 can actually handle 1mhz. I tested it myself and was able to lower my electronic gearing from 8:1 to 4:1. Runs fine at nearly 3k rpm and was able to double my step resolution for indexing. Probably irrelevant in your case since you don't need to index your c axis at insane speed. I'm sure you'll be nowhere near 1mhz even with no electronic gearing. I would give it the full 16 bit to work with. Still be able to run your C as fast as 750rpm or so if you wanted.

I'm running in analog torque mode so the DMM gear ratio does not apply. The only DMM parameter that is even active in that mode is the Torque Filter Constant, which when set to 127 is effectively turned off. All of the control and PID is done at the controller level, the DMM drive just becomes a simple servo amplifier.

We do keep learning more and more about the DMM servos, their documentation is somewhat lacking in the fine details. But like you I have been in communication with DMM support. They are very responsive.

[QuinnSjoblom]

I'm running in analog torque mode so the DMM gear ratio does not apply. The only DMM parameter that is even active in that mode is the Torque Filter Constant, which when set to 127 is effectively turned off. All of the control and PID is done at the controller level, the DMM drive just becomes a simple servo amplifier.

We do keep learning more and more about the DMM servos, their documentation is somewhat lacking in the fine details. But like you I have been in communication with DMM support. They are very responsive.

Ah ok, yeah right after I typed that I realized you probably aren't running step mode. So your controller reads error between commanded position and encoder position, then applies torque proportional to the amount of error in the correct direction. I wish mach3 was capable of closed loop control like that. Would make this so much more simple for me. In my case, I could probably even use a ring encoder directly on the spindle and get really excellent precision. Not sure there's even software out there designed for diy machines that could handle that. Maybe I should do some research. Been thinking about going mach4 which would solve a few other puzzles, butbi don't think it has closed loop either

[Jim Dawson]

Ah ok, yeah right after I typed that I realized you probably aren't running step mode. So your controller reads error between commanded position and encoder position, then applies torque proportional to the amount of error in the correct direction. I wish mach3 was capable of closed loop control like that. Would make this so much more simple for me. In my case, I could probably even use a ring encoder directly on the spindle and get really excellent precision. Not sure there's even software out there designed for diy machines that could handle that. Maybe I should do some research. Been thinking about going mach4 which would solve a few other puzzles, butbi don't think it has closed loop either

Dynomotion Kflop/Kanalog will handle that, and is closed loop at the controller, inexpensive and works well. Very well supported. I believe will also work with Mach3, and they also have their own CNC software.

I use Galil products and my own software, more expensive but I have been working with Galil products for over 20 years and I'm too old to change now. I am thinking about a ring encoder, Renishaw does sell one that is not too expensive. I'll see how the existing encoder system works out first.

[QuinnSjoblom]

Dynomotion Kflop/Kanalog will handle that, and is closed loop at the controller, inexpensive and works well. Very well supported. I believe will also work with Mach3, and they also have their own CNC software.

I use Galil products and my own software, more expensive but I have been working with Galil products for over 20 years and I'm too old to change now. I am thinking about a ring encoder, Renishaw does sell one that is not too expensive. I'll see how the existing encoder system works out first.

I'll have to check out those controllers. I'm not sure how much work I'm gonna put into this machine. I'm already working on plans for a new, much more capable machine. Very similar to the layout of a doosan puma mx mill turn. Pretty much layed out like a sub spindle lathe with y axis, but instead of a turret with static and live tools, it will just have a bt30 milling spindle with 180 degrees of b axis articulation. All milling tools and static turning tools go In bt30 holders, gives radial and axial live tool access to both turning spindles. Bt30 locks stationary for turning. Would be an extremely capable and versatile machine. Bt30 holders are cheap, so just collect like 50 of them and have most tooling setup permanently. Swap what's needed into tool changer for different jobs. Aside from the usual chuck and collet holding in the lathe spindles, I want to build larger fixture plates, maybe 5x5 max to attach to spindles for 3+2 milling, possibly clamps built in that are actuated by drawbar. Parts can transfer from one spindle to the other, possibly even a modified bt30 holder with a gripper built into it for loading and unloading bigger stock into the spindles which is grabbed out of a stock magazine. Full automation possible with larger peices, and of course bar feeding. Pretty much no limit to what type of parts it can do within a certain size (Not designed for big parts), along with full automation. That will be an expensive machine to build though. Epoxy granite main casting, 3 big servos for the 3 spindles, as well as 6 more servos for x,y,z,b,sub, and tool changer. Maybe steppers on tool changer and b axis, but at least closed loop for reliability. Also it will be getting some higher quality linear rails and at least c5 ground screws. Probably 20k to build this, but massive capability compared to what you can buy for 20k.

[Jim Dawson]

........ I'm already working on plans for a new, much more capable machine. Very similar to the layout of a doosan puma mx mill turn. Pretty much layed out like a sub spindle lathe with y axis, but instead of a turret with static and live tools, it will just have a bt30 milling spindle with 180 degrees of b axis articulation. .........

An ambitious project, I'll be watching for the build thread.

[QuinnSjoblom]

An ambitious project, I'll be watching for the build thread.

That one will be quite a ways down the road for many reasons. First of all funds, also need a real shop space, also have a lot to learn in programming to make this work the way I want. Mach3 isn't gonna cut it. mach4 will do it, but I know nothing about lua scripting and that's gonna be a steep learning curve.