My X axis belt tension screw turns, gets harder to turn and then feels loose. Resulting in a slack belt again. I can only seem to tension it to a certain point before this happens and its just a shade off not tight enough. As its anti clockwise to tighten do you think this is the screw in the Belt tensioner reaching the end of the thread? is there even enough space for this to happen inside the X carriage?
Assuming this is a picture of your setup, partially assembled then you should be able to see what happens, and if you place a set screw identical to the one you have already in the assembly on top of what we see above in the picture then you can see when the set screw being turned anti-clockwise gets to the end of its thread, at which point it will just turn without any extra tension being applied. If it does get that far then the belt isn't tight enough in the first place/it was cut too long. The limit of the adjustment will be governed by.... A. When the set screw is fully unwound from the nut (seen in the "D" shaped piece above). and/or B. When the D shaped piece is moved as far left as it will go and hits the body. I suspect that "A" is the more likely. I'm sure the answer is in the original assembly instructions (WiKi) as I vaguely remember cutting the belt to the correct length etc. and the answer now is to adjust the set screw "clockwise" almost all the way in it will go and to tension the belt where it fits with the grub screw seen above in the slot to the left of the tensioner, this may mean cutting a few mm of the belt to get it to fit. Then use the tensioner again for the correct adjustment. A thought on the different tension you feel on the set screw is that fully anti-clockwise as it disengages from the nut the head may be pushing into the plastic to the right of the set screw i.e. where the Allen key is inserted. Either way the solution is the same, re-adjust the belt.
