Hello,

in the last couple of weeks, I've spent quite some time assembling my RepRapPro Mendel, which appears to be going fine apart from one issue: I cannot get the X belt to run true. It just keeps moving towards the machine front side of the idler (moving the carriage by hand in either direction). I have tried playing with the belt tension and the position of the belt in the clamps, but to no avail. Since I cannot find any forum topics on this issue, it seems that nobody else is having this problem, so I'm guessing its solution is probably trivial. I would really appreciate some advise. Which factors are most important for making the belt run true?

Have you got the bracket that the idler is mounted on square to the X axis? You can alter it using the screws that bear on the ends of the x axis smooth rods.

When I was putting mine together I thought that keeping the belts on the idlers would be a problem but once it was lined up properly it's been fine.

I was a bit hesitant to touch the setting screws for the X bars after their careful positioning in an earlier phase of the assembly process. Following your suggestion, I tried it anyway and it does make a big difference.

Thanks a lot!