Layer shift: when a print jumps sideways mid-way

What it looks like and why it happens

On the print you see a sharp step, from which the whole part above it is shifted a millimetre or more to one side. With FDM the head position is derived from the number of steps of the stepper motors. If a motor skips a step, the printer does not know and carries on as if nothing had happened.

The most common causes are a loose belt, wrong tension, too high an acceleration, a snagging carriage, or the nozzle colliding with a part that has lifted, for example through warping.

Why the head sometimes snags

The reason for a collision is usually a layer that is slightly higher than the others, a raised edge or a loose bit of plastic in the way. The head hits it and the motor skips a step. It helps to lower the travel speed and to stick the first layer down well, see adhesion.

Mechanical causes, such as a worn belt, have to be fixed by maintaining the printer. We deal with those, not the customer.

What you can do in the model

• Avoid very tall thin pillars that wobble during printing and that the head may catch.
• Give the part a wide base on the plate so that it does not lift, see model orientation.
• For large models, consider splitting them into smaller pieces.

Where possible, split a tall thin part into two pieces that are then glued together, see gluing. A shorter part is more stable and less sensitive to collisions.

For your order

If a layer shift happens during printing, the part is spoiled and has to be printed again, which can push back the lead time. We photograph the batch before dispatch. With large slender parts it is better to adjust the model before uploading, or to send us a note.