Did you check that the grub screws on the pulley are tightened?
The pulley's not slipping on the motor shaft is it?
Maybe keep an eye on it while it's printing. You might find its slipping.
It might not be as apparent if the first layer is being printed slowly.
Edited 1 time(s). Last edit at 01/09/2017 03:58PM by FA-MAS.