Why do 3D printers use stepper motors as opposed to servo motors

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Why do 3D printers use stepper motors as opposed to servo motors

 

People have been making attempts to introduce servo motors into 3D printing for a long while. They’ve tried little boards that modify your stepper motors to give servo control and more sophisticated methods. Mainly as they can see a potential market, which if they can convince people this upgrade is worth it, they can make a little coin.

3d printer stepper motor

The truth is these things cost more than steppers. The power increase that servos offer is unnecessary as 3D printers need very little thrust. They might occasionally have to push through a slightly raised overhang from a previous layer, with a nozzle at 200–275 deg C, so literally a hot knife through butter. The position recovery a servo system will perform you might think would be useful but, 3D printers only run out of position if the motors, their current or the mechanics of the printer are not correct. The right motors, with the right current and good mechanical components and there is never a problem with being out of position, even during multi-day prints with multiple millions of lines of gcode involved. If the nozzle goes out of position the chances are your print is ruined, even if it can recover.

As someone on RepRap forum said once, position recovery is only useful if you want to be able to continue printing after someone has knocked the printer off the desk, or grabbed the x-axis and given it a yank. Neither are really likely scenarios.

Yes, the idea of being able to turn a stepper into a servo, is a good one - but more for robotics or CNCs or other similar applications.

The use of encoders in say paper printers was more about being able to use cheap (and quiet) DC motors with an encoder for very accurate position control. If you could come up with something like this for 3D printers you might be on to something, but at $10 per motor for reasonable nema 17 steppers, how much money do you think you can save?

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