Prusa i3 Print Height Too High

Hi all, I've been searching and trying to figure this out for a while and haven't found anything so I apologize if this has been asked before. I have a Prusa i3 that I have been trying to calibrate the z-axis on and what currently happens is I finally get the axis moving 100mm when I command it to move 100mm but then I go to print something, like a test object that is 50mm high and it comes out at 56.22mm. I then try to turn down the steps per mm and it causes the nozzle to collide with the print or squishes the layers so they turn out sloppy and the top is pushed up over the perimeter. Here's what I have for my Marlin axis config and what my slic3r settings are for the layers (in case that's the true issue). It's a 1.75mm hot end with .4mm nozzle and a RAMPS 1.4 board. Any help or direction would be greatly appreciated, Thanks.

#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*60, 0} // set the homing speeds (mm/min)

#define DEFAULT_AXIS_STEPS_PER_UNIT {101.7051,99.6306,3995.02841,671.2610} // default steps per unit for Ultimaker
#define DEFAULT_MAX_FEEDRATE {200, 200, 2, 25} // (mm/sec)
#define DEFAULT_MAX_ACCELERATION {9000,9000,100,10000} // 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 retracts

#define DEFAULT_XYJERK 8 // (mm/sec)
#define DEFAULT_ZJERK 0 // (mm/sec)
#define DEFAULT_EJERK 5.0 // (mm/sec)

Here's an image of two separate prints side by side, the one on the left was printed with a default steps per mm of 4500. This was where the z axis would move 100 mm when told to more 100 mm but when printing the print would come out too tall (it is supposed to be 50 mm) and the one on the right was when the height difference was put into the axis calibration here [nathan7.eu] and the new steps per mm were calculated. As you can see the one on top had the nozzle collide with it and rip it off the print bed and just created a blob at the top and all the layers are really sloppy.

If you are using standard i3 m5 threaded rods with micro stepping, then your steps per unit should be 4000. If that's not working, then perhaps your z motors are skipping steps causing erratic behavior.

Edited 1 time(s). Last edit at 08/22/2014 01:38AM by brucehvn.