Skewed print of gear wheel - other prints OK

Hi,

I'm trying to print a bevel gear, and it's coming out a bit distorted.

I do have some minor calibration issues with cubes, but it seems much worse on this print.

The gear has an internal hexagon shape to accept a bolt/nut, and it's here where you can really see the issue. Picture attached. Hopefully you can see that 2 sides of the hexagon are much longer than the others.

The faces of these longer sides are oriented diagonally with respect to x and y, so it is not a simple matter of x or y being out.

Using Repetier Host, when I tell the printer to move in X or Y in manual mode, the moves are accurate to below 1%, so it's just this gear that goes wrong.

My steps per mm are calibrated for all axes and extruder, my stepper drivers are trimmed correctly, my bed is nicely level. Other objects I've printed are near perfect.

Any clue where the calibration issue might lie?

I am using the latest versions of Repetier host and firmware under Ubuntu 12.04

Thanks

James

This is backlash on one (or both axis).

Check that your belts are adequately tight and there is no slop in them.

-Rob A>

Thanks very much. Makes sense.

I actually have a metal rack and pinion drive on both X and Y, and there is a bit of lash in the mechanism.

I have seen the backlash settings in the firmware I think, so I'll play with those.

Thanks again. I managed to reduce lash mechanically on the rack and pinion to less than 0.1 mm, and the problem has gone away.