I've just been testing a timing belt drive that connects a Lichuan servo motor to the cross slide ballscrew of my lathe. The parts I used are:

150-3M-15 Timing Belt (150 long belt)
32-3M-15 Metric Pilot Bore Timing Pulley (32t driven)
16-3M-15 Metric Pilot Bore Timing Pulley (16t driver)

I have the belt nicely adjusted but when I turn the motor against the locked ballscrew using my fingers, I can clearly see the best part of a mm or so of movement between the pulley and the belt at each pulley before the teeth of the belt and pulley actually make contact. This is crap, as it equates to something like 100um of backlash and sort of negates the cost and ballache of bothering with a half decent ballscrew and bearings. I'm fairly certain this isn't to be expected.

The belt is a Transflex brand and the pulleys are fairly generic looking items, all from Bearingboys in the UK.

Has anyone seen similar issues and if so, what would you suggest? I could buy (hopefully pukka) pulleys from somewhere like RS in the hope the pulleys are the issue.

I may have to get out the calipers and make some measurements but I don't have a standard or drawing to compare against, only the belt and the pulleys themselves. It feels to me that the pulley teeth aren't deep enough, causing the belt not to seat fully. Not something I was expecting to have to deal with....