Ramps running multiple steppers - how??

Working on a larger scale printer, Using RAMPS 1.4, and since the z axis already can handle 2 motors, I figured why couldnt the x & y?
So I built a simple rail system using 2 x motors driving belts. it does seem to work, however, at higher speeds it tends to "grind" on direction changes. Not a belt skipping, but its almost like the motors are magnetically becoming uncoupled. the funny thing is I can run it with 1 motor and its "better". So im thinking theres some backfeeding going on between the motors - kinda like when you turn the reprap z axis and the other side turns.
Is there any way to isolate these motors? Id really like to use 2 because of the carriage weight.
Or - at very least a diffrent type of controller with isolated steppers that can be "programmed" to both be x?
Thanks!
Jeff

If you have connected both motors in parallel, then they share the current. So each one only produces around half the torque of a single motor. That may not be enough, bearing in mind the extra friction and inertia that the second motor + any associated drive mechanism brings. Increasing the current setting on the driver boards should help, if the driver boards can take it.

If you connect the motors in series, then at low speeds both motors work at full current and full torque. However, at high speeds there may not be sufficient voltage to drive both motors at full current. The solution is to increase the voltage to the stepper drivers. But with RAMPS, this will also increase the voltage to the hot end heater, even if you use a separate power supply for the heated bed..

Edited 1 time(s). Last edit at 01/03/2015 08:02PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

The Steppers were connected in Parallel just like the Z axis is wired on the board.
I did not connect them in series as I wasnt sure how to. which colors connect to complete the series circuit?
I did upgrade the drivers to the Purple board - 32x stepping, but made little difference.

See [reprappro.com] for how to connect 2 stepper motors in series.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Ok, looked at it and understand - however, I need the motors to turn opposite each other.
Also, Ive never heard anyone wiring these up this way until that link you showed - anyone have their motors wired this way? Does it work ok?
Thanks!

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I need the motors to turn opposite each other.

Simply swap the wires of one(!) winding of the motor you need to reverse.

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anyone have their motors wired this way?

Sure, I use serial Z-motor wiring for all my printers - works perfectly as long as steppers have a low impedance.