Y axis drifts only at a certain point

So i have been printing a few calibration boxes through thingiverse and all seemed to go well. This is my first print. I decided to try to print a gear from wades extruder and it was going great but it appeared to go south during the middle of the print. The print began drifting during the second half of the gear. I have a Hic Prusa i3 with Marlin. I have checked the belt and set screw on the gear (Y axis) but all seems fine. I have been slicing with Slic3r and printing with repetier server. Here is the url to the gear. http://www.thingiverse.com/thing:65939/#files

I am trying to print the biggearmod_fixed_1.stl. If you look at the gear, the first half prints fine, but at the start of the second half, all goes wrong.



Attachment 8638Attachment 8639

I have 2 3d printers and every thing works heating, melting, and the plate heats, but as it get's to the point to start printing it goes to the home corner and stops and starts making a loud noise, if I leave it the noise stops and the head tries to go to the start point but doesn't get there it starts to zig zag and just move around a little at which time I stop it. I have tried every thing I know to get it to work but even my other printer is doing the same thing????? Any help ????? Thanks Ron.

What speed are you prinint at? The Y-axis stepper needs to pull the weight of the build table to and fro. It may be that the Y-axis stepper motor is skipping steps when it (or the electronics) get warm.

You can check this by reducing the printing speed by at least half and trying to print again. If the print then goes well, you can try to increase the current to the stepper by adjusting the pot on the stepper board. Turn it a little clock-wise to increase tha max current. Also check all cables and the soldering of the connector on the main board.

It may also be that you have found the mechanical upper limit of what your Y-axis can handle.