Random Movement

Hi,

I'm new to the forum, new to 3D printers, and new to Python.

I have a self-assembled Prusa Mendel with Wade's Extruder. I installed Arduino 0023, Arduino 1.0.3, Python 2.7.3, PYSerial 2.6, wxPython 2.8, PYReadline 1.7.1, Pyglet 1.1.4, Pronterface, Skeinforge, and Sprinter - all Win32 on Windows 7 x64.

I'm trying to print the test file '20mm-box.stl'. It starts off by printing a rounded square, then a rectangle (20mm x 17mm) inside that. Then it tries to print the fill, but looks nothing like a square, kinda random. Then when it tries to print the second layer it just goes in totally random directions, all over the bed.

Anybody know what I might be doing wrong?

Thanks.

Are there little pauses between the random moves? That would suggest too much current in the stepper drivers. If they overheat, they shut down until they cool again. That can happen in less than a second, causing several moves to be skipped.

No pauses.

Does the gcode look correct in Pronterface? Does the machine always move correctly when moved manually from Pronterface? Everything is calibrated and homes correctly?

For the first 10 seconds, the printer moves fine - after that, the motors will randomly make partial movements and clicking sounds. I'll try to adjust the stepper driver current.

Thanks Dale.

Yes, I agree that it sounds like the symptoms of stepper skipping. It could also be a mechanical cause of stepper skipping, as in binding or too much friction. I had to rework my bed several times to get the friction and binding out.