Two Z Motors

[thefoxburrow 0]

Hi everyone!

I'm in the process of developing and sourcing my own 3D printer based on the UM2.

Since my design has a significantly bigger and heavier build platform, using two motors on the Z axis seems to be appropriate. I plan on wiring them up in parallel and connect them to the standard Z port on the UM2 mainboard, because they should basically do the exact same thing simultaneously.

My question here is whether there would be any problems for the mainboard delivering the required power to operate these motors.

I plan on using these motors: http://www.robotdigg.com/product/29/Nema17-60mm-1.5A-high-torque-stepper-motor

in combination with fairly tight threaded rods, to minimize the torque needed to move the build platform.

Thanks in advance

 

[aviphysics 9]

The nice thing about using separate ports would be th ability to auto level the platform. Mostly useful for when the motors are powered off and the two sides can slip somewhat indepently.

I think the biggest problem with two motors and seperate drivers would be the possibility for self destruction, if one driver burns out and the other keeps ticking. This could be avoided by driving both motors from a single driver, but that might have some other undesired effects, if the impedence of the two motors is not a very good match.

I think I would be inclined to use a single motor and connect the threaded rods with a gt2 belt and pulleys.

[thefoxburrow 0]

The only possibility i see to use two ports would be sacrificing the port for the second extruder. considering the loss of this option and the problems which come with it (e.g. destruction if one of the motors fails) this doesn't seem to be the way to go.

My idea of using two motors wired to the same port in parallel is one viable option (hence my question whether there would be any problems in the electronics), the other being the belt driven rods with one motor. The latter has some problems with the torque needed to move the relatively heavy build platform (I calculate around 9.5kg for this piece, due to aluminium as a heat distributor and glass as the actual surface), but the idea of using one geared motor just came to my mind, so this appears to be the current best solution to my problem.

Auto bed leveling using two motors wouldn't really be possible, because the two rods are solely used for moving the platform up and down, while the platform is guided by four 12mm smooth rods (one for each corner) using square flanged linear bearings, prohibiting any unleveling once the platform is leveled.

 

[aviphysics 9]

Andendum to my last post...

If you wired the motors in series, it would help ensure proper load balancing, (because both motors would get exactly the same current.) It would also mean that if a connection failed on one of the motors, the other wouldn't get double its rated current and wouldn't keep moving while the other motor stalled.