Stepper Robot

Has anybody ever heard of an industrial-grade 6-Axis robot designed around stepper drives instead of servos? Seems like it would be lower cost.

Just curious...

TM

At a company where I use to work, the owner insisted that I look into creating such a beast for exactly that. It was never built for three main reasons:

First, for stepper motors to be as powerful as their nearest counterpart servos, they end up being much larger. This increases their relative cost and creates a number of other cost increases elsewhere.

Second, by its nature, the stepper motor has no feedback of its own. Rather, it attempts to go where it's told but if it doesn't get there, oh well. It's still satisfied. Now, of course, you could add your own encoders or other feedback device, but there go some of those cost savings again. If you don't add them then you never know when the system will get out of sync - and on a multi-axis machine that can never be good.

Third, your servo controllers have a whole bunch of capabilities and control-ability already built in. Those aren't too available otherwise.

Anyway, that's my 2-cents. Steppers have their uses, but not on a multi-axis machine where coordinated moves are typically needed. Servos all the way.

Steve