Prusa i3 z axis motors

Having a problem with my stepper motors on my new prusa.

When the threaded rods are not connected the motors work great!

When I hook up the threaded rods, the motors don't work. I get humming.

I'm guessing not enough power some how.

......any suggestions?

what speed are you trying to run them at? If I run my z at more than 6-7mm/s they fail to turn at all.

I have no idea what speed.

I am using Marlin.

I'm asssuming I can program at Marlin?

You need to set it in the marlin configuration file.

I'll assume its one of these lines of code.......

//// MOVEMENT SETTINGS
#define NUM_AXIS 4 // The axis order in all axis related arrays is X, Y, Z, E
#define HOMING_FEEDRATE {50*60, 50*60, 4*50, 0} // set the homing speeds (mm/min)

#define DEFAULT_AXIS_STEPS_PER_UNIT {79.46,80.2,4042.8,744.54}// default steps per unit for 12 tooth T5 Belt
#define DEFAULT_MAX_FEEDRATE {500, 500, 5, 45} // (mm/sec)
#define DEFAULT_MAX_ACCELERATION {9000,9000,100,3333} // X, Y, Z, E maximum start speed for accelerated moves. E default values are good for skeinforge 40+, for older versions raise them a lot.

#define DEFAULT_ACCELERATION 3000 // X, Y, Z and E max acceleration in mm/s^2 for printing moves
#define DEFAULT_RETRACT_ACCELERATION 3000 // X, Y, Z and E max acceleration in mm/s^2 for r retracts

//
#define DEFAULT_XYJERK 20.0 // (mm/sec)
#define DEFAULT_ZJERK 0.4 // (mm/sec)
#define DEFAULT_EJERK 5.0 // (mm/sec)

If you have a ramps board, see here http://reprap.org/wiki/Pololu_stepper_driver_board

It is possible that your motor current is too low, or, indeed the speed or acceleration too high.

Check the maximum current spec for your z motors. Then set the Vref on the stepper controllers to the voltage corresponding to no more than the current rating of the motor. If you're motors are wired in parallel, then you should be able to set for twice the maximum current rating.

Edited 1 time(s). Last edit at 01/21/2014 12:20PM by brnrd.

Thanks all, it ended up being not enough power.

Adjusted the power at the stepper motor driver and is working fine.

Sjerguy, can you please tell me how did you adjust the power at the stepper motor drives? I am having a similar issue on my Prusa i3. Z-axis motors work fine alone, but they do not work, when both are connected.

Are there any special power settings to be adjusted? If there, how can I do that?

Very tiny screws at the very bottom of the stepper cards. Make sure you use the correct card.

Put one meter lead on the negative power terminal and the other touching the potentiometer centre. Adjust to about 0.4 volts initially.

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Waitaki 3D Printer

Alternatively... run a copy of RampsTestCode which will try to excercise all servos. Adjust the set screw on each stepper until the appropriate axis (or extruder) just moves and then go another 1/4 turn.

Wisar