This fix applies to all Ultimaker 2 series machines, and Ultimaker 3 series machines. You will need your 2mm hex head screwdriver or 2mm allen key to apply this fix.
Keeping strong tension on the short belts that connect your X and Y motors to the pulley system that moves your printhead is key for accurate prints. If the belt tension isn't tight enough, you might end up with ovals where you wanted a circle.
One good way to check the tension of your belts is to feel them by hand. You can also print a minical and take a look at how it came out. If your print appears to be missing steps on one of the axes (giving you an oval instead of a circle), but your overall print isn't tilting to the side, one of your short belts is loose.
If your whole print seems to be slanting sideways, you probably have a loose pulley, and should check out this page for more information.
To resolve a loose belt problem, you will need to loosen the four screws holding the motor in place, and apply downward pressure to the motor while tightening the screws again. The holes that the motor screws are in are slotted to allow room for adjustment. The motor screws are identified by the washers between the screw head and the panel. Your Y-motor screws are visible on the left panel, and your X-motor screws are visible on the back panel. If you need help locating them, check out the screw diagram for your printer at the link below:
- Ultimaker 3/Ultimaker Extended Screw Diagram
- Ultimaker 2+/Ultimaker 2/Ultimaker 2 Extended+/Ultimaker 2 Extended
- Ultimaker 2 Go
For a demonstration of the process, take a look at the video below.