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In a discussion about motors with a friend who used to work in the robotics industry, he told me that he despised stepper motor systems, as every stepper based system he had worked on required a bunch of hacky software fixes to make the system perform to the required level.

He said that servo motor based systems had their own foibles, but at least they could generally be tuned out and you always knew that if the encoder said you were in a given place then you would be (to within the constraints of the backlash compensation).

Because of this, I was wondering if there were any options for using brushless DC motors + encoders + drive electronics instead of steppers + drive electronics.

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  • $\begingroup$ Given that there are robotic servo arms that are used for 3d printing. What you really want is a DC motor with an encoder. $\endgroup$ – StarWind0 Apr 12 '17 at 17:19
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You can get "stepper replacement" servo drives that supposedly put all the needed control in the drive, and accept ordinary stepper inputs. Those should make the servo-drive a "drop-in" option on anything that uses stepper drives.

That said, I've seen an affordable CNC router system based on steppers turned into a much more expensive system based on servos, and I still have the "obsolete" stepper version, as the servo based system is MUCH more expensive and I could not keep up with the "upgrades" and never would have bought it at the price it now goes for. I'm in fact considering changing that to a reprap control system (still as a router, not as a printer, as I currently think.)

Given some practical limits to printhead speed in additive 3D printing based on the material solidifying, there may not be a lot of benefit in the considerable added expense of servos. They can move faster, but how much of that will translate to actually printing faster? How fast can you melt and pump plastic and have it stay where you put it?

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I think using these technologies is possible, and may be better than stepper motors, but by using these you loose the main advantages of the steppers : the simplicity and the cost.

When you use steppers, you assume your motors are strong enough to don't loose any step, and you "just" command them. Steppers are not so expensive and are compacts, so your 3D printer is "simple".

If you use separated motors and encoders, you can do better job, but your 3D printer will be a lot more expensive, harder to tune, and harder to program.

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  • $\begingroup$ I wouldn't agree with "harder to program" -- you just need a different driver. $\endgroup$ – Carl Witthoft Apr 12 '17 at 13:04
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    $\begingroup$ Yeah, by "harder to program" I mean the control engineering part. With steppers, you don't even think about it, you just suppose the motors follow the command. $\endgroup$ – Fab-B Apr 12 '17 at 14:45
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    $\begingroup$ The question is "[are there] any options for using brushless DC motors + encoders + drive electronics instead of steppers + drive electronics?". You're giving your own opinion of why steppers are more commonly used rather than servos, but this does not answer the question of whether there exist any servo-based 3D printers (they might very well exist even if you think a stepper-based system is better). $\endgroup$ – Tom van der Zanden Apr 22 '17 at 7:33

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