Upgrading stepper motors from 76oz/in to 92oz/in, worth it?

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This topic contains 10 replies, has 6 voices, and was last updated by Profile photo of Jeffeb3 Jeffeb3 3 months, 1 week ago.

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  • #27164
    Profile photo of Saaif
    Saaif
    Participant

    I don’t know if this has been asked before, but would it be worthwhile to upgrade the stepper motors in the MPCNC from the 76oz/in ones in the kit to 92oz/in, which are the highest NEMA 17 torque I can find?

    http://www.omc-stepperonline.com/nema-17-bipolar-stepper-motor-65ncm92ozin-21a-17hs242104s-p-21.html

    What advantage would I gain? Right now I can easily cause the steppers to slip with a good yank on the gantry, but I haven’t seen it slip while cutting so far.

    Just wondering if anyone has any ideas…

    #27179
    Profile photo of Barry
    Barry
    Participant

    Don’t see a reason to do this. The current steppers can bend the tubes on some of our larger builds.

    #27183

    That’s the ones I use. They work great. The more torque the better, but as Barry just said, it is useless if you don’t have a very stiff structure, so either reinforced tubes or small CNC size.

    In my opinion, the biggest advantage to have torquey motors here is that it will give you a bit more freedom of mind, since you will better trust your CNC to work fine even if you are not constantly around. Wood is an inconsistent material, you have some soft and some hard spots even in the same plank, so the amount of torque needed is not constant and not previsible at any point. Having more torque means that you are a bit safer regarding the risk of missing steps on some hard spots.

    Don’t forget to take into account that these motors will be heavier and longer than the other ones.

    #27186
    Profile photo of Jeffeb3
    Jeffeb3
    Participant

    Meh, I’m not even maxing the current I could be using with the steppers I have. If I needed more torque, I would start with that. But on my 3’x4′ build, the steppers aren’t the limiting factor.

    #27203
    Profile photo of Ryan
    Ryan
    Keymaster

    How are your steppers currently wired?

    #27227
    Profile photo of Saaif
    Saaif
    Participant

    My steppers are currently wired directly to one driver each. No parallel or series, I’m using all 6 slots on the Ramps board with Estlcam set up to use all 6.

    I find it hard to believe that these steppers can bend the tubes, especially when I can cause then to slip with a good yank. That’s mostly what I’m worried about as well, because I was recently cutting bamboo and my workpiece slipped and even though the dewalt stalled, before it did that, the stepper slipped and lost a whole lot of steps.

    16oz/in of extra holding torque might make it more rigid, but that’s why I’m asking, because I’m not sure.

    In my 2.5′ x 2.5′ machine, the place it flexes the most is where the belts attach to the zip ties, but apart from that it’s been great. I’m just trying to find ways to improve this machine, haha.

    #27233
    Profile photo of Ryan
    Ryan
    Keymaster

    So let me back this up a little bit.

    You can’t just brute force drag a sharp object through wood and expect good results.

    A proper cut should have very little force exerted on the machine at all. Proper feeds speeds should cut like a hot knife through butter. I would work on your setting before you do anything else.

    Try using a full sized router by hand on wood and mess with your amount of force, if you push hard enough to stall it all sorts of things are wrong about that. There is a proper amount of force for every material, and for wood it is very very little.

    Everyone is so quick to jump at a bigger router and bigger steppers and more voltage. CAM is a science and it is peoples full time very well paying jobs. There are a million things to learn.

    If you drive a Lamborghini to the grocery store doesn’t mean you will get there any faster than a driving a Volkswagen bug, you can only drive as fast as the conditions permit.

    #27260
    Profile photo of Saaif
    Saaif
    Participant

    Fair enough, I’m aware that there are better ways to approach things, all I’m asking is if there will be an improvement to using more powerful steppers, and if there are improvements, where would they be?

    I’m cutting bamboo, and it’s nothing like what I’ve worked with in the past. To be honest it’s more like aluminum more than it is like wood, as strange as that sounds. I’m just trying to find ways to improve my MPCNC, and I just happened to come across these steppers and I was wondering if they would make a difference.

    #27271
    Profile photo of Ryan
    Ryan
    Keymaster

    I would spend the time testing gcode and different cam techniques, rather than spending the money, but that’s me. I built a budget cnc…

    I have a few videos milling IPE, that is some of the worlds most dense wood, bamboo should be easier (I assume). Have a look at my videos and my settings to get you going down that path.

    #27300
    Profile photo of Bill
    Bill
    Participant

    I would imagine bamboo is so fibrous that it’d be really easy to get the bit to tear instead of cut. Proper speed and RPMs should allow a bit to deal with it as well as normal wood. Maybe too many flutes or too fast? You want the cutting surface to have time to get a bite.

    #27307
    Profile photo of Jeffeb3
    Jeffeb3
    Participant

    If you are skipping steps, and you don’t think you should be then increasing the driver output should also help, but you run into heat issues. I don’t have mine set at near the theoretical max, and I feel that they are strong enough already.

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