Adding microstepping driver to FSL Retina Engrave?

Electronics related to CNC

Adding microstepping driver to FSL Retina Engrave?

Postby TLHarrell » Thu May 15, 2014 8:22 pm

I've got a question from a different forum. A guy is thinking over the concept of changing out the motor/stepper driver board for something that supports microstepping. There appears to be some sort of setting in the Retina Engrave software that hints at this being feasible regardless of FSL stating that the machine physically needs to be 1000 steps per inch to be supported. His theory is to try to reduce some of the "coining" on the laser cut edges of parts.

Does anybody have experience using the Retina Engrave controller board with a microstepping driver? If so, do you have any comparison for quality running at higher microsteps vs. the native 1000 step per inch?
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Re: Adding microstepping driver to FSL Retina Engrave?

Postby Cre8ivdsgn » Mon May 19, 2014 9:36 pm

Your post made me think about Copley Controls and their stepnet products. Stepnet can be configured for just about any step resolution, but it also takes encoder feedback. And the encoder feedback doesn't need to match the step size. You can go up to 4096 microsteps per step but at some point you limit max velocity.
Anyway, operating with an encoder on the stepper, you could effectively have any feedback resolution you wanted because the stepnet driver translates the received step/direction pulses to what is effectively a servo setup. For example, configure the driver to 1000 steps per inch of motion (or fraction of rotation). Now add a US Digital low cost (relatively!) encoder to the motor and you can suddenly get 10,000 ppr (E6 encoder) or what is effectively 50 microsteps per step.
The Copley drives are nice compared to some others because it handles the step/encoder relationship seamlessly. Other drivers I've played with need the encoder resolution to be an integer multiple of the stepper resolution.
So as far as FSE stuff is concerned, I think it could be done, but now add the cost of the stepnet drivers, encoders, and additional wiring and this route may be cost prohibitive. (Roughly, stepnet $240/axis, encoder E6 $109, wring ? and you are looking at $350 per axis at least.)
I think you could even go another route with the Copley drivers. There is a setting that allows configuration of input step equaling X microsteps. Normally this is 1=1, but you could set it so 1=50. So now 1 FSE step is 50 microsteps. No encoder required.
I don't work for or sell Copley. They are expensive in one sense, but there is a shocking amount of capability in the driver (CAN Bus communications, full blown motion profiles - a mini-motion plc of sorts, and more etc's than you can shake a stick at.)
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