extruder stepper stops working

I've got a newly built Prusa Mendel with a RAMPS 1.4 board running Marlin firmware being driven from Prontrface. I'm more or less calibrated and have printed a couple of calibration pieces. Hurrah.

Just the other day, the extruder stopped printing part way through a print. Bah.

I find that when every thing's just fired up from cold, and the hot end has reached temperature (240 deg) I can extrude and reverse, but after a short while the extruder doesn't respond to extrude or reverse commands. This is repeatable. Once it's stopped, I can turn the extruder gear by hand and it extrudes plastic OK. This suggest that the polulu stepper driver isn't sending anything to the motor (the command appears in the Prontrface console though). The motor is not hot and is clearly not energised, yet it starts off working properly. The other motors are all working fine.

I'd appreciate any suggestions as to how to tackle this.

Cheers, Chris.

Having same problem, did you have any luck?

Is the pololu overheating and shutting down?

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Waitaki 3D Printer

Have watched a print and it takes about 5 mins to stop. driver at that stage was only warm to touch. same as it normally is

I think I've fixed it. I moved the Polulu board to a different axis on the RAMPS board, and the problem followed the board, although in a different way: I moved out to the z axis, and it cut out after a period of working. Eventually decided to inspect the board under magnification, and saw one of the header pins had a dubious-looking joint. I re-soldered the joint, and it looks to working right - ran off a test print with no problem.

Mine is sorted. Driver was set very marginally too high.