Ticking noise somewhere on the Y axis

Hi everyone,
I’m hunting a short, sharp ticking (or clicking) noise without success in the last days. It sounds comparable to a hot exhaust system on a motorbike when it’s cooling down. Anybody has an idea which part could be responsible?
What I know about it:
.) Occours repeatable during all steady moves of the y-axis, but not on fast travel moves
.) Happens 1 per Y-stepper revolution
.) Source must be somewhere under the print bed, not from stepper itself or the bearing on the other end of the belt.
.) Doesn’t affect print quality

I can’t find anything, the belt runs free, no wires interacting with it. Rods and bushings are looking good as far as I can tell without disasembling the hole thing. No visible cracks in the parts…

Check the belt mount under the bed itself. There is often a short piece of unsecured left over belt sticking out that is usually out of the way, but it could be sticking out sideways and hitting the teeth of the other belt as it moves. Aside from that, it could be debris in the Igus bushings, a loose mount screw on the bushing holders or the belt mount, or potentially a loose rail mount on the frame?

So, now I did what I wanted to avoid: Removed the Y frame… Then I recognised that the sound has to come from the stepper, it seems to come from the bed because the belt transfered it to the aluminum plate.
I removed the pulley from the stepper, first because I thought it might have a crack (thinking on the thread with the cracked Z coupler). Couldn’t find anything, stepper turns just fine. Now everything is back in place, no ticking up to now… Let’s see if it comes back when printing tomorow.

You might have had a loose pulley setscrew, and when you put it back on, tightened it enough that the belt wasn’t hitting the protruding head anymore.