My OMTech 60 W laser cutter has a stepper motor Z axis drive that has worked flawlessly since it arrived. However, it recently developed a periodic klonk during autofocusing and manual jogging, loud enough to shake the platform and rattle the cabinet’s bottom plate.
A few minutes of poking around revealed the klonk happened on each turn of the Z axis leadscrews, which quickly led to finding the cause:
It’s a rectangular wood chip, perfectly sized to jam into the Z axis motor pulley driving the belt: a belt tooth lifts up on the chip as the pulley turns, then klonks as it slips off the other side. The motor pulley and all four leadscrew pinons have the same number of teeth, so they’re all at the same point in their rotation when the belt slams down onto the pulley.
Where might such a thing come from? Well, I recently finished a batch of plant markers and hadn’t yet cleaned out the “chip tray” which is also just the bottom plate of the cabinet:
I briefly considered building a guard for the motor pulley, but the belt most likely carried it from elsewhere. The leadscrews have an ample coating of grease that was also smeared elsewhere on the cabinet, making the belt sticky enough to catch such things.
The chip tray is once again pretty clean and the platform behaves normally again.
That was easy …
The Smell of Molten Projects in the Morning 
I am forever incredulous at people who aren’t sensitive to mysterious “clonks” and other such anomalous noises. I guess they’ve never made the correlation between them and the trouble that they frequently signal. It’s like they can’t even hear them.
My unpowered hearing is bad enough that I must depend on Mary for anything in the treble, but our rule of thumb is “no noise is good noise”.
I make exceptions for squeaks in the back door and basement door, because knowing when those move is a Good Idea. :grin: