When something breaks, it gets improved.
I was in the middle of a job when I hear a pop and see the chain on the far side of the table suddenly go slack.
Turns out the shaft of the motor on that side of the gantry had just sheared off (the pic shows it with the drive sprocket still attached).
This, boys and girls, is why you never leave a CNC machine unsupervised. I was able to stop the machine immediately before it messed up the job in progress. I could still jog the gantry around the table, since that motor is one of two that drive the x axis, but I would not be able to maintain any accuracy farther than a foot or so from the side that still had a motor.
Thankfully, that was enough to make new motor mounts. As you can see, they are a huge improvement over the old mounts, which were cobbled together back when I was figuring out how best to drive the x axis (I should really write a back-dated post about that). Other than being much cleaner and more solid, they also incorporate a feature that should prevent this from happening again: support for the motor shaft.
As you can see from the pic above, the drive sprocket was on the very end of the motor shaft, so when I applied tension to the chain it was actively pulling down on the shaft. No wonder it eventually broke. With the new mount, the end of the motor shaft is supported by a bearing, so the force from the chain is distributed.
I also finally got some cable track for all the cords! I haven’t quite finished setting it up, but I’ll post some pics when I do!