[SwampDonkey]

Hello to all!
If I put this in the wrong place then I apologize in advance.

I bought a used Tormach several months ago. The thing randomly misses steps for reasons I havent been able to deduce. Ive cleaned, oiled, greased, and adjusted gibs to no avail. It's time for some new motors. I really want to go to something with feedback (servos) as opposed to the open loop stuff. After the Tormach destroyed a few critical parts, I just dont trust steppers to do what they're told. Im fully aware that a properly working stepper setup can be virtually as capable as one with servos, but I need to know that the machine will at least fault out instead of mangling stuff.

I still cant afford the high end AC servos or slick "servo-steppers" from Leadshine, so Im thinking some big DC servos with maybe Viper drives. I hope to control the machine with the K-flop, or at the very least the Smooth-Stepper.

My power supply on the machine puts out 72V to the drives, with a "healthy" amperage of unknown quantity.

So, what do you guys think my best option is?

Thanks!

[mactec54]

SwampDonkey

The Dmm servo system/package would be the best way to go for your machine, price as well is most likely better than what you were thinking of using

DMM Technology Corp.

[109jb]

I haven't implemented it on my machine yet (G0704 converted to CNC), but I have experimented on the bench with adding rotary encoders to stepper motors. This is not a closed loop feedback setup, but rather a way to detect missed steps. The way it works is that the stepper runs just like an open loop stepper with the encoder sending the actual position back to the control software. If the actual position (from encoder) differs from the commanded position by a preset amount the machine will stop. It won't restore the position to where it should be like a true closed loop system, but if steps are missed the machine will stop and probably save the part. I have experimented with it on the bench with the setting set to stop the machine if the actual differs from commanded by more than 0.003" and it seems to work well, but it may be a while before I get it on my machine since it is in storage while we build a new house and barn/workshop. I am hopeful that it could work down to 0.001" so that if the stepper loses even one full step it will fault out. I did this on linuxCNC, but I have heard that you can do it in Mach 3 as well with a macro of some kind. Might be something to think about.

[samco]

I would think that the tormach is direct driving the ball screw with the stepping motors. So - I think you are going to need some hefty servos to replace the steppers. The next option would be a timing belt reduction.. (this is just my 'feeling' - you would have to do the math)


(that being said - linuxcnc would be my choice with mesa hardware (they even have servo drives - but almost any +/-10v servo drive would work) Closed loop back to the control

sam

[SwampDonkey]

I would think that the tormach is direct driving the ball screw with the stepping motors. So - I think you are going to need some hefty servos to replace the steppers. The next option would be a timing belt reduction.. (this is just my 'feeling' - you would have to do the math)


(that being said - linuxcnc would be my choice with mesa hardware (they even have servo drives - but almost any +/-10v servo drive would work) Closed loop back to the control

sam

Yes, its direct-drive, which means I would likely have to have a belt reduction for anything under 500W. Linux CNC would be awesome, but Im under the impression that its not very user friendly, which I need as an amateur who cant program at all.

[SwampDonkey]

SwampDonkey

The Dmm servo system/package would be the best way to go for your machine, price as well is most likely better than what you were thinking of using

DMM Technology Corp.

I would LOVE to have a DMM setup (400-500W would be perfect) but I cant afford to pour over a grand into the machine at this point. Ive never used servos for anything, and would like to see what DC servos/ drives would be capable of matching/ exceeding the steppers in performance. The fact that Mach3 uses step/dir output somewhat limits what I can use as well.

[samco]

I know it sounds scary. Linuxcnc is running on ubuntu which is one of the more user friendly operating systems. Having to 'program' has not been true with linuxcnc for ages. You can if you want to but between what linuxcnc calls HAL (hardware abstraction layer - a way to hook componants togather virtually) and its integraded ladder - you can do pretty much anything without a lick of code. Also - I think there is already tormach configs.

git.linuxcnc.org Git - linuxcnc.git/tree - configs/tormach/

so - you could try it out as is with your steppers just to play around with linuxcnc. (although you might want to email tormach and see if they have anything more current)

the docs are pretty extensive and are constantly being updated

LinuxCNC Documentation - HTML version

Yes, its direct-drive, which means I would likely have to have a belt reduction for anything under 500W. Linux CNC would be awesome, but Im under the impression that its not very user friendly, which I need as an amateur who cant program at all.