XY axis shifts, more commonly referred to as layer shifts, are when an extruder or bed shifts during a print and continues in a different area of the build plate. Parts may look perfectly fine other than everything being shifted on one particular layer.
There are quite a few causes for layer shifts in the X or Y axis. One easy to diagnose cause is when the extruder is prevented from moving by an obstruction.
The most common way this occurs is when there is a tangle in the filament or it is not feeding correctly. We have experienced brand new filament spools that are tangled straight from the factory, which cause a layer shift hours into a print. It is important to store your filament properly and keep the spool tight with either tape or putting the end through a hole on the side to prevent this.
Other problems can arise from unlubricated rods and stepper motor malfunctions. If the bed or carriage has a stepper motor that is stiff or is has a pulley that is harnessed loosely, skipped steps will occur. Skipped steps in the motor will almost always cause a layer shift. When a print has multiple layer shifts but continues the entire print, it is likely not due to a filament tangle, but rather stepper malfunction or roughness on the rods.
As mentioned in the Jogging and Homing section, lubricating the rods is extremely helpful in preventing layer shifts. The likely best prevention method that can be implemented is having proper storage of your filament. Once you are done using a spool, you should always keep everything as tight as possible and make sure it cannot unravel or become tangled.
As mentioned in the Filament Options section, 1.75mm filament is more flexible while on the spool, making feeding much easier. While we prefer 3.00mm filament for its better tolerances in diameter, we have experienced layer shifts when a spool is near the end and it just doesn’t feed properly.
Since stepper motors are mechanical parts, they will eventually wear down. Periodically check your belts to make sure they are tight and that the stepper pulleys are moving smoothly