pulley spins belt slips

[mcmental]

evening all, just setting up my small plasma table and when i am jogging the axis it will go so far then the motor and pulley spin but the toothed belt seems to not grip. this happens when it is halfway (approx 450mm) down the Y/A axis, is this down to the belt not being tight enough causing some flex? the belts are fastened down on either end via a 5mm tee nut and grub screw.

thanks in advance

chris

[beefy]

No idea what you mean when you say "the belts are fastened down on either end via a 5mm tee nut and grub screw". Do you mean the pulley.

Even so you say the issue is the belt seems not to grip. So do you mean the belt is slipping around the pulley, i.e. the teeth are disengaging.
Synchronous belts should have just about zero stretch, so the only way I can see them disengaging from the pulley is if there is not enough tension, or the mechanical system has some flex somewhere, and the pulley shaft is not held rigidly in place.

Also, seeing as it seems to happen at a certain position on the axis, I would remove the belts and push the gantry and Z axis by hand to see if there are tight spots somewhere.

[djreiswig]

I'm guessing the belt is a single strand that runs the length of the table and the motor is mounted on the gantry.

[mcmental]

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[adbuch]

It looks like you have a cogged belt (with teeth) so as long as the belt is tight it shouldn't slip. I would follow Keith's advise and test by manually moving your gantry (with power off) to see if you have a particular spot that is causing binding as you move it along the path. Also I see the cogged belt/pulley, but don't understand what the belt is driving. Does your table use rack and pinion, or is it simply relying on gravity to keep the drive wheels on the tracks?
David

[mcmental]

There are 4 bearings on the top as you can see and 4 underneath the rail too, maybe the bearings need more friction, I will strip it and try pushing my hand later today.

[robertspark]

belt tension required. when I used belts I had some tension springs made similar to these (I used HTD 5M belts. 20mm wide and the cheap tension springs were not available in my size required.

https://openbuildspartstore.com/timing- ... on-spring/

they are available from many outlets

[adbuch]

There are 4 bearings on the top as you can see and 4 underneath the rail too, maybe the bearings need more friction, I will strip it and try pushing my hand later today.

Yes - if you are only using bearings for wheels and have no rack and pinion, then your setup would be more prone to slipping.
David