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  1. #1
    Muzzer's Avatar
    Lives in Lytham St. Annes, United Kingdom. Last Activity: 14 Hours Ago Has been a member for 3-4 years. Has a total post count of 294. Received thanks 39 times, giving thanks to others 5 times.
    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....

  2. #2
    Muzzer's Avatar
    Lives in Lytham St. Annes, United Kingdom. Last Activity: 14 Hours Ago Has been a member for 3-4 years. Has a total post count of 294. Received thanks 39 times, giving thanks to others 5 times.
    Duplicate
    Last edited by Muzzer; 23-02-2021 at 09:28 PM.

  3. #3
    Muzzer's Avatar
    Lives in Lytham St. Annes, United Kingdom. Last Activity: 14 Hours Ago Has been a member for 3-4 years. Has a total post count of 294. Received thanks 39 times, giving thanks to others 5 times.
    Nobody seems to be able to reply to this post - I must have annoyed the timing belt gods!

    I hope you don't mind me pasting the guts of your PMs as a sort of manual reply method:

    From Voicecoil:
    I used AT5 belts (Syncroflex) and pulleys from Beltingonline and got good results - approx +/-10...15um final accuracy. There are different tooth profiles available for belts, the main ones being trapezoidal (lowest backlash) and trapezoidal (best power transmission), I'm wondering from what you said about the teeth not seeming to reach the bottom that maybe your belt is a different profile from the pulleys? Hope this is of some help, Trevor

    From m_c:
    Have you tried knocking a flange of a pulley, so you can see how well/poorly the teeth mesh?
    They should be a pretty tight fit without any movement.


    I'll have another look for alternative versions but after a first look I couldn't find an equivalent small pulley of a similar diameter to the 16t one. However, I have a flangeless pulley on the motor, so may be able to look more closely at how the belt and pulley mesh. I'll look at beltingonline as an alternative supplier, as I can't help thinking this is a quality issue.

    Thanks for the replies!

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