Are 200 step/revolution steppers adequate w/belt drive?

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reflectivist
Posts: 1
Joined: Thu Apr 12, 2012 6:35 am

Are 200 step/revolution steppers adequate w/belt drive?

Post by reflectivist » Fri Apr 13, 2012 4:07 am

I notice that in your Shapeoko.com store there are 400 step/revolution 62 oz/in NEMA 17 motors and
200 step/revluation 60 oz/in NEMA 17 motors for sale, currently. The 400 step motors are slightly
more expensive. Since a belt drive CNC machine translates axle rotation to linear more directly than a
lead screw does (e.g. belt moves further per revolution), is there a significant benefit to using a 400 step
per revolution stepper vs. using 200 step per revolution motor? Do stepper motor controllers that offer
micro-stepping (1/2, ... 1/16 step) modes make the200/400 step tradeoff a non issue?

I have some 200 step/revolution NEMA 23 motors (280 oz/in), that I planned to use in a larger CNC
machine, roughly based on the Shapeoko design, using MakerSlides, (I also ordered the Shapeoko mechanical kit).
I'm wondering if I should to consider a lead screw instead of belt drive to get adequate stepper resolution
with 200 step/revolution motors. (I assume Shapeoko avoids the lead screw to avoid backlash?)

I haven't built CNC equipment before, so I don't have a lot of experience with the tradeoffs involved, and
would appreciate the input/insight of people with more background in this area.

Thanks,
Paul

pourcirm
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Joined: Mon Apr 09, 2012 6:25 pm
Location: Saint Louis, MO
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Re: Are 200 step/revolution steppers adequate w/belt drive?

Post by pourcirm » Fri Apr 13, 2012 4:38 am

This topic was actually discussed in the Google Group that was used before Edward started the forum. Here is what Edward had to say:
Regarding the steps/rev: 200 or 400 won't really matter in our case. The difference in resolution is obviously 1/2, but in reality you're not going to see that sort of performance and unless you're building an STM the difference is probably unnecessary.

I know we all like the idea that "more is better", and I'm guilty of that just as much (or maybe more!) than the next guy. But when sourcing your motors, remember that 200 steps per rev is just fine.

To prevent the "if that's the case why did you point to the Sparkfun motors?" question: Here's the answer: They're accessibly, and a great price. The fact is that I couldn't find a better price (for order qty of 3) than the Sparkfun motors, they just happen to be 400 steps/rev.. If someone can find a better price, for 200 or 400 steps/rev motors, let me know and I'll link to them on the BoM.

-Edward
Basically from what has been said the important thing about the motors is that he knows the Sparkfun motors are priced well and that they work. There are numerous options out there depending on what you can get your hands on. It sounds like the biggest things to keep in mind are trying to get motors of the right size (NEMA 17 or 23 for the X and Y axes, and a NEMA 17 for the Z axis) and with a holding torque at or even above the 60 oz in mark.

- Ryan

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