pulley bore tolerances, 5mm +/- 0.02mm is that ok? (added a video)

I bought the following item

[www.ebay.com]

I was expecting the pulley to be more tight fit, I can feel how the timing belt becomes tense and less tense when it spins due to the eccentricity of the pulley..

Is this normal? I'll try to post a video

Edit: here is the video: [youtu.be]

Thanks

Edited 1 time(s). Last edit at 02/19/2014 06:53PM by xchip.

if your pulley is held on with a grub screw, and the shaft hole is too big then it will run off-center.

for now, you can put some aluminium foil / pie tray around the shaft to make up the difference in size, for that price the pulleys are probably quite low quality.

the belt definitely shouldn't get tighter and looser as it moves

Adding a video to show the eccentricity

[youtu.be]

Is this normal?
Cheers

No that's not normal somebody sent something wrong or your shaft is different than what you thought did you measure it.

That's a lot worse than +/- 0.02 mm. The eccentricity of the pulley translates to error in positioning by the same amount. I wouldn't use that pulley without some way to center it.

The motors I am using are a Nema 17 and have a 5mm shaft, and are the ones used for the makerbot, they even have 'MakerBot' engraved on the back.

Quote
xchip
The motors I am using are a Nema 17 and have a 5mm shaft, and are the ones used for the makerbot, they even have 'MakerBot' engraved on the back.

you going to need something to measure with by a cheap set of dial calipers you can usually get some cheap ones less than 20 bucks maybe eBay. Anybody that has a printer should have at least a set of dial calipers so you can measure your parts to calibrate and check printed parts. You have to find out what's wrong at the moment I would assume the pulleys you bought were wrong but you need dial calipers to see what's wrong do you know anybody that has some. You can take pully and motor over to his house or invite him over with calipers

Edited 1 time(s). Last edit at 02/20/2014 11:55AM by cnc dick.