knocking noise during and after print

I get this knocking noise during and after prints. The noise doesn’t start immediately when I start a print.

Does anyone know what’s going on? How can I fix it?


When do you first notice the sound on the Z-axis stepper motor(s)? Is it just one? When was the firmware last updated?

I think it’s just one of the steppers making noise (left Z-axis I think). It’s not in the first few layers, but definitely 10 minutes into a print.

I’m running

Send: M115
Recv: FIRMWARE_NAME:Marlin  (Aleph Objects Inc.'s Phabricator) SOURCE_CODE_URL: PROTOCOL_VERSION:1.0 MACHINE_TYPE:LulzBot Mini EXTRUDER_COUNT:1 UUID:351487b6-ca9a-4c1a-8765-d668b1da6585


I discovered that my case fan wasn’t spinning. It seems I forgot to plug it back in when I installed the USB protector (

I will try some prints and write back.

I had what I believe to be the same issue. Your latest comment got me to pull the cover off of my mini and check the wiring. Sure enough, the controller fan plug had worked its way off of the Fan2 header. I plugged it back in and performed a test print and all is right again.