Random Large Shifts (10-20 mm)

Hi I am new here and new to RepRap. Not sure where to post this so trying here. If i should put it some where else please let me now.

I just finished my Meldel build and working on getting it calibrated. I have got it printing the thin wall box just great. When i try to print the solid or hollow or anything else I have tried it will print great untill about +-1/2 way though where it will shift +- 10 mm on x axis. After shift it either keeps printing correctly at the shifted point or at next layer it will shift another 10 mm and keep shifting at every new layer.

I have no clue how to fix or trouble shoot this.

I am running RAMPS 1.4, using printrun with slic3r.

any help would be fantastic

Printing problems are better suited for the general section and get faster/more responses.

I had this issue with my two printers as my motors are not quite powerful enough and I had the pololu maxed out. I put the little heatsinks on them and added a computer fan and the drivers stopped overheating and skipping steps.

If you feel/measure the temp of your drivers that will let you know if your running to hot.

Sounds like skipped steps. Heat sinks and a fan on the board would be the first thing I'd do. While you're at it make sure your pulleys are tight as well. The power for the board fan can be tapped off the input to the RAMPS or if you are using an ATX PSU you can use one of the circuits that aren't being used.

change the accelration from 3000 to 1000 in slic3r

One should be able to use the stock Slic3r acceration profile on a basic buld with no issues but like everything else there may be exceptions. I mentioned to check the pulleys and belts because if they aren't configured optimally the acceleration (or other movement) may cause them to jump which results in skipped steps as the motor steps don't transfer to the drive mechanism. In that case it's a mechanical issue and using software to compensate for it may not be the best solution compared to addressing the actual issue.

Change the accerlation helped for me,
Also dont set the print speeds to fast, Average 50-60 mm/s is enough.

Also i have a 120mm fan blowing on it always, i did print a cover for it so if it ever falls from my desk, it wont hurt the cables that are at the side from it
I also have heatsinks, but i aint sure if those were enough

hay guys thanks so much for the help. It turns out it was the motor drivers over heating. i put a fan on and it seemed to do the trick.

thanks again.

Tim