Y axis variable resistance
I am assembling a MK4S kit. I have the Y axis together and I noticed something unusual. When you move the bed back and forth you get varying resistance. sometimes it will move easier and sometimes harder. In the hard spots it is resistant enough that you can get it to stay in place when the printer is rotated 90 degrees. I do have kit experience. I have assembled a MK4S before. I checked that printer and the Y axis moves smoothly and evenly along it's length.
I checked everything I can think of. The motor shaft is straight and rotating smoothly. The pulley rotates cleanly. The belt is straight. There are no obstructions in the Y axis path. Has anyone ever had a similar experience? Is it safe to try running it this way? I'm not sure what to do on this one and would appreciate anyone's insights.
Disconnect the Y belt. Is it smooth now?
Cheerio,
RE: Y axis variable resistance
yes, it is very smooth with the belt disconnected.
OK. While the belt is disconnected turn the Y motor by hand; you should feel the steps but otherwise it should be smooth, no grating, no variation in resistance.
Check the idler pulley is not clogged, out of line, or damaged (with the belt loose try turning it with your fingertip, is it smooth?)
Make sure you have fitted the drive pulley the correct way up, make sure the grub screws are correctly positioned against the flat.
Check the smooth rods are not damaged/scratched.
Retighten the belt until it just begins to make a low musical note when plucked... Then follow Prusa's tightening procedure.
Is it still smooth?
If not, contact Prusa Support via chat; you will need your serial number.
Cheerio,
RE: Y axis variable resistance
I did end up working with Prusa support. After going over everything the support tech said that this was not unusual and that it was safe to proceed with the build. I will post here again once I have it completed and describe the outcome.