# Not quite a CNC question



## JPigg55 (Nov 21, 2014)

Okay, I’ve been wanting to put power feeds on my Clausing 8520 mill. In a vain attempt to save a few $’s, I ordered the PF from CDCO, but was unable to make it work. From others, I know a Servo type 140 PF will work. However, with a prive tag between $600 and $1000 each plus mounting kits turns into a bit of sticker shock.
Eventually I’d like to get into CNC, but think I’d rather go with something like a Tormach or Precision Matthews when I do. So what I’m contemplating is getting a 3 axis CNC conversion kit to use stepper motors instead of PF’s and set it up to control them manually. Looking at going with an Arduino control system mostly due to wanting to use Arduino for other applications.
Unless it becomes necessary to add ball screws, I’m planning on sticking with the original acme screws. According to Jim Dawson (http://www.hobby-machinist.com/showthread.php/28282-Servo-Motor-sizing), NEMA 34 steppers in the 1200 oz-in range should work though he stated I’d need to gear them if sticking to the acme screws. I’d rather just direct drive instead of messing around trying to gear or belt drive them.
I haven’t completely ruled out the possibility of doing a full CNC conversion, another reason I’m considering stepper motor drives over power feeds.
I’ve been looking at Automation Technologies (http://www.automationtechnologiesinc.com/) though I haven’t shopped around too much yet. Most of theirs seem to be closed loop hybrid steppers. For my purposes, I don’t think I need that style, but I could see the advantage in a full blown CNC conversion. From my very limited knowledge of CNC, closed loop would mean no missed/partial steps.
So beyond the Arduino control portion, what else would I need besides the stepper motors, power supply, and drivers ?
Would 1200 oz-in steppers work with a direct drive set-up using the acme screws or would I be better off changing over to ball screws or bigger motors ?


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## DMS (Nov 21, 2014)

It should be fairly doable. The motor sizing is going to depend on how much force it takes to turn those motors. Those seems like decent sized steppers, but steppers loose torque rapidly as their RPM increases. Most documents I have read about using steppers recommend against gearing down, because you end up having to spin the motor faster, and end up losing torque. It all gets very complicated though, and it will depend on the specific motor, and the specific load. If you arrange the motors to run off of a belt, then you can start with a 1:1 ration, and change if you like. If you go with a helical coupling or other similar coupler, you are going to be stuck with a fixed ratio. Given that you are not planning to go CNC right away, a belt drive system would make it easier to keep your handles.

As far as other stuff, you will need some switches for forward/reverse and stops, as well as a potentiometer to control speed. You will also need some way to couple the motor, and some hardware to mount the motor.


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## bloomingtonmike (Nov 22, 2014)

You may be limited on amperage for your steppers with an arduino based shield. How will you interface the higher amperage stepper drivers?


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## bladehunter (Nov 22, 2014)

As long as the drivers have an opto coupler amperage wouldn't be a problem.

Just for a bit of info, Linux CNC runs on the beagle bone black, could be a simpler way of running the steppers, upgrade to cnc should be somewhat easier.


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## JimDawson (Nov 23, 2014)

I guess I should jump in here.  The 1200 In-oz motors should work OK as power feeds with an Acme screw in direct drive.  I would not trust them to be accurate in a CNC configuration, too much chance of missed steps.  If you later convert to CNC with ball screws, then they will be fine.

EDIT:  I should note here that in order to get 1200 in-oz out of the motors, you need to run them with 70 volt drivers and power supply.  They will run on 24 or 48 Volts, but not at full torque


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## JPigg55 (Nov 23, 2014)

bloomingtonmike said:


> You may be limited on amperage for your steppers with an arduino based shield. How will you interface the higher amperage stepper drivers?



The Arduino is just the controller outputting through the drivers to power the stepper motors. At least that's what I get from the Youtube videos. Search Youtube for "Use Arduino to control large stepper motor".


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## JimDawson (Nov 23, 2014)

JPigg55 said:


> The Arduino is just the controller outputting through the drivers to power the stepper motors. At least that's what I get from the Youtube videos. Search Youtube for "Use Arduino to control large stepper motor".



Normally the drivers take a 5 Volt input for the step and direction, at about 20 mA.

I should note here that in order to get 1200 in-oz out of the NEMA 34 motors, you need to run them with 70 volt drivers and power supply. They will run on 24 or 48 Volts, but not at full torque


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