Shifting on Axis

My new Prusa I3 had been working pretty well. Was still a little calibration to be done but I was able to print some spare bits and also some larger pieces. Suddenly I am having it shift on the y-axis (in the positive direction) to the point where I can't print! Belt tension seems ok, I have worked on the trim pot's, and think they are tuned ok, but I am still suffering. What is the most likely problem?

Cheers,
Wisar

Check the pulley. Make sure it is not slipping. Also check the wiring, could be one of the connecters has slid out of the housing.

Connections look good (store bought and then wiring soldered) and I can not see the belt slipping though I am not sure exactly how to check! It looks and feels like the same tension as always has been.

Thanks for the tips......
Wisar

Sounds like the pully is spinning on the motor shaft. this will give a false movement. The motor steps will be correct, but the motion will be out.

I really thought we had the answer when one of the two set screws was quite loose and the other not as tight as the two on the x-axis. But alas, three or four layers in, and we started to drift again. Always to the positive direction...

Wisar

when this kinda issue happens with me, its normally something is loose...
try slowing down the speed see if it happens, try and isolate the issue, make sure the smooth rods have no grime on them and that every movement is smooth..

sometimes these things can be so obvious we forget to check the basics..

one time i changed the x carriage, put it back together and i was printing ovals instead of circles, Could not understand why..
30 minutes later i saw that the belt was on the knob of the pulley not on the teeth so the OD was much larger and hence why it was printing oval and not circles ..

Blush. Looking for the obvious payed off. It also helped to ask myself the question...did anything change between when it was working and when it was not? I had 'improved' my setup to try and keep the power and thermistor leads from the hot bed out of the way of things. This entailed an elastic 'spring' that must have been putting just enough force on the table to cause my issue. Getting rid of the 'improvement' and I am printing without slipping again.

Thanks to all for the advice,
Wisar