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Thread: What effect does microstepping have on torque?

  1. #85
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    Default Re: What effect does microstepping have on torque?

    Quote Originally Posted by UA_Iron View Post
    Your paper was compelling, I would have gathered the same facts from it had PCW_Mesa not come in and give his input.

    In industry I use Schneider M-drive stepper motors. We run them at 52000+ steps/rev or ~256 microstepping. The torque curves are not derated for higher microstepping values, but there are electrical limitations where the DSP capabilities fall off - I imagine greater than 256microstepping for most controllers is an issue in that sense. We load these motors to 70% of their rated load (over the ideal 50% or 2x safety factor) and they have never stalled out due to running torque. We are super repeatable; I took a 10um resultion (8um accuracy) linear encoder provided by balluff and did a series of studies, we were extremely repeatable on a C10 ballscrew actuator over 1000mm. I will have to pull that data out if I can find it.

    Ultimately, if your system is behaving the way you want it to at the settings that you have it at, then you've met your requirements (I just kind of repackaged what you said in this sentence here).

    I'm always up for a good discussion, good information here.
    Its funny you mentioned dsp. this is the first machine ive run with dsp drivers, It is two slaved drivers running my y and both do the same thing at 10x and above, Sorry you got me thinking that might have something to do with it. The fact they both do it the same and i have other axis same drivers running higher settings, i dont think it could be that.

    voltages all very stable, with surplus watts available with just the two 5a drivers set at 3.7a per 48v 800w psu so not there.

    Like i say they are on 20:1 reduction boxes, geared back up on the pinion but still a reduction good reduction and the errors im seeing are far too large to be magnetic backlash, at worst around 0.15mm.

    I have no other explanation than due to heavy load, the motors are at the top of there rated load range and are more susceptible to drops in torque, and that i am getting a drop. but then again motors stall at 8m/min, seeing issues at 5.5m/min. suppose this comes back to this holding vs stall torque and the drop is therefore just with holding torque?

    Going to have to stop thinking about this otherwise its going to drive me nuts

    Anyone got a torque wrench and and un unused motor they don't mind welding together?

    Last edited by Jon.N.CNC; 10-22-2015 at 06:55 PM.


  2. #86
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    Default Re: What effect does microstepping have on torque?

    Can anyone explain how motors/drivers compensate for inefficiency? I.e the heat the motors generate during Holding?

    Doesn't seem to be factored in to any of the papers I've read on torque and microstepping.

    Or is that because it's irrelevant?



  3. #87
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    Default Re: What effect does microstepping have on torque?

    Quote Originally Posted by Jon.N.CNC View Post
    Can anyone explain how motors/drivers compensate for inefficiency? I.e the heat the motors generate during Holding?

    Doesn't seem to be factored in to any of the papers I've read on torque and microstepping.

    Or is that because it's irrelevant?
    It's because they are operated exactly like a servo-mechanism and require the encoder as position feedback. When a position deviation is detected, then the compensator function applies current to the motor to go back to the intended position.

    Documentation, literature and theory of operation is kind of weak on the internet to be honest. This is because the use is typically commercial but is spreading into the consumer world. In the commercial and industrial applications these drivers are sold through distributors who are application experts.

    I had a copley controls stepnet driver setup with a stepper and encoder feedback. It requires software to tune your stepper motor, set some gains, set other parameters. It's cool to have a stepper powered up, and grab the shaft to rotate it and feel the driver compensate nearly on the fly to prevent that movement.

    I can never guarantee the operation of anything on ebay, but if you're interested in messing around with one of these drivers for a low price:
    Copley Controls Stepnet Digital Stepper Digital Drive Model STP 075 07 | eBay

    Then there's the chinese leadshine
    2PH 57mm Nema23 2 2nm 5A 1000LINE Encoder Closed Loop Stepper Motor Drive Kit | eBay
    DSP Closed Loop Step Motor Drive Kit 20 50VDC 3PH 4A 3nm Nema23 57mm Engraving | eBay

    not sure how tunable the above are, and I have no experience with them - the effort spending in making the above listings work might negate any benefit you get from them when all is said and done.



  4. #88
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    Quote Originally Posted by UA_Iron View Post
    It's because they are operated exactly like a servo-mechanism and require the encoder as position feedback. When a position deviation is detected, then the compensator function applies current to the motor to go back to the intended position.

    Documentation, literature and theory of operation is kind of weak on the internet to be honest. This is because the use is typically commercial but is spreading into the consumer world. In the commercial and industrial applications these drivers are sold through distributors who are application experts.

    I had a copley controls stepnet driver setup with a stepper and encoder feedback. It requires software to tune your stepper motor, set some gains, set other parameters. It's cool to have a stepper powered up, and grab the shaft to rotate it and feel the driver compensate nearly on the fly to prevent that movement.

    I can never guarantee the operation of anything on ebay, but if you're interested in messing around with one of these drivers for a low price:
    Copley Controls Stepnet Digital Stepper Digital Drive Model STP 075 07 | eBay

    Then there's the chinese leadshine
    2PH 57mm Nema23 2 2nm 5A 1000LINE Encoder Closed Loop Stepper Motor Drive Kit | eBay
    DSP Closed Loop Step Motor Drive Kit 20 50VDC 3PH 4A 3nm Nema23 57mm Engraving | eBay

    not sure how tunable the above are, and I have no experience with them - the effort spending in making the above listings work might negate any benefit you get from them when all is said and done.
    Thanks UA Iron, yes with a closed loop system it's almost an irelevant factor. It's more open loop systems where there is little feedback, In fact after writing that post I remembered how drivers, with dsp drivers doing this more often, measure motor inductance and trim output current acordingly to improve repeatability. I suppose this is how.



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What effect does microstepping have on torque?

What effect does microstepping have on torque?