Z Axis Grinding

I just got my Prusa i3 fully built and (mostly) functional, but I'm having an issue with the Z axis. If I set the DEFAULT_AXIS_STEPS_PER_UNIT to the defaults I've found online, 80,80,4000,915, the motors will both grind when stepping up, down, or going home, which you can see in this video:

[www.youtube.com]

Then, if I try changing the Z steps to 3657.1, which I've also found as a good rate, the up and down motions will work fine, but home still grinds: [www.youtube.com]

I've noticed if I try lowering it to something like 600, it won't grind going up, down, or home. But then everything is incredibly thrown off and print height will be completely wrong. I'm still new to this so maybe i'm missing something obvious. Here's that whole section of my Configuration.h:

// default settings

#define DEFAULT_AXIS_STEPS_PER_UNIT   {80,80,3000,915}  // default steps per unit for Ultimaker
#define DEFAULT_MAX_FEEDRATE          {500, 500, 5, 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

// Offset of the extruders (uncomment if using more than one and relying on firmware to position when changing).
// The offset has to be X=0, Y=0 for the extruder 0 hotend (default extruder).
// For the other hotends it is their distance from the extruder 0 hotend.
// #define EXTRUDER_OFFSET_X {0.0, 20.00} // (in mm) for each extruder, offset of the hotend on the X axis
// #define EXTRUDER_OFFSET_Y {0.0, 5.00}  // (in mm) for each extruder, offset of the hotend on the Y axis

// The speed change that does not require acceleration (i.e. the software might assume it can be done instantaneously)
#define DEFAULT_XYJERK                20.0    // (mm/sec)
#define DEFAULT_ZJERK                 0.4     // (mm/sec)
#define DEFAULT_EJERK                 5.0    // (mm/sec)

If it matters I'm using 3 mm abs filament with a .35mm nozzle.

when your having M5 for the z-axis with 1/16 microstepping and 1.8 degrees motors your steps/mm must be 4000 see: [prusaprinters.org]
Lower your max feedrate for the z-axis from 5 to 2.

Edited 1 time(s). Last edit at 01/25/2015 03:00PM by gforce1.

Quote
gforce1
when your having M5 for the z-axis with 1/16 microstepping and 1.8 degrees motors your steps/mm must be 4000 see: [prusaprinters.org]
Lower your max feedrate for the z-axis from 5 to 2.

Looks like that's what I needed. Thanks!