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Thread: help: stepper motor recommendations

  1. #1
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    Default help: stepper motor recommendations

    I added a post to this thread (third page) asking for recommendations for steppers, but I thought that subject might warrant its own thread for others to read too.

    So disregarding my specific machine, what stepper motors work well with Mach3 and a Gecko driver. I think those of you with experience in this sort of thing (John, Evan, Weston, etc.) would have good advice to offer. OF course there are other good drivers and softwares out there and the same motors ought to work as well with any of them, I just mention Gecko and Mach3 because they are very common/popular and it's what I have too. I figured maybe some recommendations could be made for a range of machines from small like mine to larger ones so others could read this and apply the advice to their own project.

    So I guess the question is, for CNC motion control, are there recommended stepper motors to use in terms of brand, specs. etc.? Are they all really about the same and should work if you have the right stuff driving them? Seems like the ones I see on eBay are about the same as the ones Kelling sells but I don't know - maybe they are different and it's just hard to tell. They appear to be generic "no-name" steppers but have similar specs to the name brands for less money, etc.

    The reason I ask is my little CNC machine has pretty awful performance from the little steppers I'm using. Maybe they are just too small? They are Nema23 and a little less then 40mm long. They have the standard 200SPR and are 4-wire bipolar motors. With Mach3 and Gecko drive, they have very rough and noisy motion at slow speeds which doesn't seem like it ought to do at all. My Y-axis was working OK at first when tuning motors via Mach3, but after setting a few things differently, that axis got to where it doesn't even turn, though it makes the noises as if it's receiving the driven signal from Mach3. Just not turning. And I can't make it go at all now for some reason. Just thinking maybe I need to upgrade my motors a notch or two and want to get something decent this time so I can get past it and move on. Seems like every move I've made so far has netted zero or backwards progress and I'm getting frustrated.

    Well thanks for any help.

  2. #2
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    Default

    NEMA 23 Stepper Motor: KL23H276-28-4B

    4th up from the bottom.

    http://www.kelinginc.com/NEMA23Motor.html

    Good all round motor as regards performance and price, you could even drop down to this one if price is an issue.

    4: NEMA 23 BIPOLAR STEPPER MOTOR 185 oz-in KL23H256-21-8B

    This is the motor we fit on the rotary table conversions.
    .

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.




  3. #3
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    Another choice is the motors sold by Mariss at Geckodrive. They are matched to the drive you purchased.

  4. #4
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    Thanks for the recommendations. Short & sweet is good I guess.

    I wonder if I'm way under on my power supply. According to the formulas I've seen, it seems that the max voltage always ends up between 60V and 120V. I am using a 24V 6.5A supply and so far just tuning one motor at a time so I'm sure the amps are plenty adequate. But is 24V going to cause a stepper to perform this badly?

    I have hooked it up to a desktop and it is pretty much identical bad performance, if not a little worse. One motor seems to work OK, one just sits and makes noises and the third is noisy at slow RPM and doesn't like to know which direction it's supposed to go at any speed. Maybe I just have really crappy or even broken motors. The two that don't work performed OK on the cheap chinese driver and the one that works OK now didn't work very well at all on that driver. Aarrgh!

    So maybe I'm even looking at a higher voltage power supply. But the G540 is only rated to a max of 50V so I'm not sure if I should push it with a 48V supply or if that would be OK. The normal one in between is 36V so that's just one notch up. Would that likely help anything or do you think 24V would be low enough to cause the problems I'm having?

    I'll look around here and see if I can find a different stepper in the boneyard. I don't think I'll have any luck there, but I might get lucky and find something to hook up and test the drive.

  5. #5
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    At work we only use 24v on small motors like nema 17 and 11. Nema 23 motors we tend to run at 36v, 34s at 36 to 60. The 42s have dedicated drives at run at something like 170v.

    Almost all of the drives we have are Geckos with a few centents and MSI drives mixed in. When the centents or MSI drive dies we replace them with geckos. About the only time a gecko dies is when someone runs over a cable and shorts them to ground or something like that. Then I can usually fix them by replacing the burnt out mosfets.

  6. #6
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    There is a formula for voltage , something like 32*SQRT(Inductnce). The higher the inductance of the motor the more voltage needed for a chopper drive to cram the current through the coils in the time it has to do it. Yes, driving steppers at 24V can be quite miserable if you want them to move rapidly and yes at low voltage and high acceleration they can stall stitting on the bench doing nothing.

    In general you want bipolar motors for this application. They will usually have 4 wires, two for each coil. It's real easy to hook the coils up wrong and get motors that do nothing but make weird noises. I assume the motors you have are known and you have a data sheet for each that gives the coil colors and polarity?

    The Gecko will handle it's rated voltage. The Chinese drives often use driver ICs that will pop thier tops, litterally, when the motor generates back EMF that well exceeds the ABSOLUTE MAXIMUM rating of the IC. This spike EMF is generated even when you run the voltage inside their stated maximum. The IC has to be able to absorb that spike and usually the spec for the power it can absorb is the real limiting factor. They cut and paste the maximum operating voltage as the drive spec but in reality you should be leaving a good bit of headroom. Geckos are not based on a driver IC and they are designed to be run at the rated voltage, no problems. The headroom is designed into them.

    A favorite of folks running the G540 is the KL23H2100-35-4B. 381oz in and 2.8mh of inductance. Max voltage would run about 53V. Its a perfect match for that driver. Grab a 48V power supply and you should be golden.
    Last edited by photomankc; 05-28-2012 at 02:09 AM.

  7. #7
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    OK Thanks. I will keep my ear to the ground for a 48V supply just to get better torque out of them (I guess that's what it does doesn't it? I wish I wasn't so green).

    But good news !!! I can slap my forehead mightily now because I DID dig up a spare stepper to try, then while diving in to hook them it to the terminal strip I installed in to connect the motors to the connectors, I discovered that the two bad-running motors had one loose wire on each of them. I am surprised that they worked at all or that the Gecko didn't fault out.

    So I fixed that bonehead move and I now get smooth motion with what seems like plenty enough torque for this little thing (we'll know that for sure a little later). Slow feed of 1/2 IPM is smooth on all three axes. I think these motors might be working on 24V OK because they are almost as small as a NEMA23 comes. They are 4-wire bipolar.

    No wonder I was confused and frustrated. So the emergency is over and I guess I'll be able to keep a little money in my pocket. Plus I learned something about the KISS principle - not that I won't have to learn it over and over again, but it will probably keep me thinking that way for a few days anyway.

    Thanks guys.
    Last edited by tyrone shewlaces; 05-28-2012 at 02:18 AM.

  8. #8
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    Quote Originally Posted by tyrone shewlaces
    But good news !!! I can slap my forehead mightily now because I DID dig up a spare stepper to try, then while diving in to hook them it to the terminal strip I installed in to connect the motors to the connectors, I discovered that the two bad-running motors had one loose wire on each of them. I am surprised that they worked at all or that the Gecko didn't fault out.
    I have a mobile robot I made with steppers and it did the same exact thing for the same exact same reason. If they start acting wonky it's time to check the wiring.

    For steppers... volts = speed, while amps = torque. More to it than that but that's the story more or less. More voltage means higher rapid speeds more amps means better torque. You can get the rated torque from a motor at 6V, you just can't keep the shaft spinning at high step rates. All the voltage does is make it possible for the driver to actually get all those amps moving through the coil they are supposed to be moving through in the time that it has to do it before your asking for the next step.

    Inductance is the resistance of the coil to changing current flow..... electrical inertia so to speak. More voltage helps overcome that resistance faster.

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