Quote Originally Posted by JAZZCNC View Post
Just about every industrial Stone cutting machine uses Helical R&P.
That doesn't necessarily mean that R&P is 'the ideal solution'. Hate to say the obvious but if everyone jumped off a cliff would you join them? R&P is great for a number of things, I think primarily where you have a very long travel. Is it ideal for a machine where you primarily need smooth slow speed movement in a travel length acheivable by a screw? I don't think so but thats just my opinion.

Quote Originally Posted by JAZZCNC View Post
Your also Wrong about the Resolution and Micro steps because no one who runs steppers would run at FULL step 200ppr.
Yes sorry if it came across as me suggesting you use fullsteps. Of course you should use microstepping. What I should have mentioned is... referring to my link http://www.micromo.com/microstepping...-and-realities

"The real compromise is that as you increase the number of microsteps per full step the INCREMENTAL torque per microstep drops off drastically. Resolution increases but accuracy will actually suffer.

The consequence is that if the load torque plus the motor’s friction and detent torque is greater than the incremental torque of a microstep successive microsteps will have to be realized until the accumulated torque exceeds the load torque plus the motor’s friction and detent torque.

Simply stated, taking a microstep does not mean the motor will actually move!"

A microstep doesn't guarantee movement. For my point about wanting a high resolution for smooth slow speed to be valid and useful the resolution has to be real world accurate resolution.

So how many microsteps can you guarantee? Well ofcourse your motor could stall completely, but lets put that to a side for a moment. 1 microstep/full steps you can guarantee them. 2 yeah thats fine. 4 probably OK. 8 maybe I wouldn't be confident. More than that I would say you definitely couldn't call that guaranteed accurate movement.

From the point of view that over doing it is better than under doing it, using 200steps/rev for this calculation means you definitely will get that accuracy. However realistically 400/2microsteps or 800/4microsteps is probably the right thing to base the calculation on.

When the machine is built you can still run it at whatever microsteps you like, nothing stopping you doing that.

I'm suggesting something like 20mm pitch screw with 1/3 belt drive. 20mm/3 = 6.6mm / 400 = .016mm or / 800 = .0083. 0.016mm - 0.0083 real world accuracy. Or better yet a 10mm pitch screw with a belt drive.