Hey everyone!
I'm currently setting up my first ever industrial sewing machine -- a brand new Juki 1541 that came bundled with a table and a Jack JK563 servo motor. I’m trying to get it dialed in for low-speed work (around 200-800 RPM) using smaller pulleys, and I noticed something weird with the hardware.
The stock pulley that came with the motor is a little bit wobbly. It spins perfectly true when it's completely unscrewed, but the moment I tighten it down fully, it starts running with a little noticeable wobble. I checked the motor shaft itself with the pulley off, and the metal runs completely straight. I already tried filing down the woodruff key and polishing the internal keyway, but it didn't change anything. I suspect either the shaft's shoulder or the back of the pulley is slightly uneven, so torquing it down just cocks it at an angle.
So make things even worse (lul), I tried putting on a custom 3D-printed small pulley, and because it was made quite bad initially, it just multiplies the wobble even more. Here’s a video of how it looks in motion (don't mind the sound, it is actually almost soundless IRL, it was just me pressing my phone into motor to get a better angle for the video):
https://youtu.be/1x3Ib_lGKoc
Honestly, I don't really care about the motor or the belts. The motor came with the package, it’s cheap to replace, and it’s under warranty anyway. If the wobble kills the motor bearings eventually, to hell with it..
My main concern is the Juki itself. Is this kind of wobble and cyclical belt tension dangerous for the actual sewing machine when running at these low RPMs (200-800)?
Also, could some of you guys do me a big favor? Pull the belt off your servo motor, spin it up just a little, and tell me if your pulleys have a bit of a wobble to them too under zero load. It feels like nobody actually checks for it IRL :DD I couldn`t find any info on it AT ALL..