# Something better than timing belts



## mullikinb (Aug 4, 2014)

Hello, I have a Shoptask Eldorado that I have converted to CNC.  I'm trying to remove all the back lash.  I have ball screws and spring loaded ball nuts, but now I find there is slight movement between the timing belt and the toothed pulley it rides on that drives the feed screws.  Has anyone else fixed this problem?  I'm curious to hear your solutions or recommendations for other belt systems.  Thanks in advance, Bob.


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## JimDawson (Aug 4, 2014)

mullikinb said:


> Hello, I have a Shoptask Eldorado that I have converted to CNC.  I'm trying to remove all the back lash.  I have ball screws and spring loaded ball nuts, but now I find there is slight movement between the timing belt and the toothed pulley it rides on that drives the feed screws.  Has anyone else fixed this problem?  I'm curious to hear your solutions or recommendations for other belt systems.  Thanks in advance, Bob.




Normally this a caused by pulley and/or belt wear.  About the only fix is new belts and pulleys.  The only other possibility is that there is a type mismatch between the belt and pulley.  There are a few different tooth forms.

Gates Poly Chain Belt has a rounded tooth form that is pretty positive.


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## astjp2 (Aug 4, 2014)

we hold .00001 tolerance on million dollar mills with timing belts, check for tension and any mismatch of parts.  tim


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## countryguy (Aug 5, 2014)

I have the Shopmaster 2010 Eldorado Gen 1 Patriot.   I can send you some Pics of what I have when I get back home later in the week.   How much play or slop would you say there is?     I have contacted JT the Shoptask owner and primary email support lead so often that he knows me by name.   He's never complained about my q's no matter how odd.   and I bought a used unit w/ aftermarket stuff as well.  Really a great guy.      Anyway -   On my unit, the belts are tight, but not overly tight.   I cannot feel any slop and the precision of my table is as good as can be expected imo.


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## Ebel440 (Aug 10, 2014)

Check that the belts fit the teeth correctly and that the pulleys are not loose on the shafts. If the pulleys are just attached with a set screw make sure they are not slipping or able to move. I have seen timing belt pulleys on cnc mills where almost half the tooth was missing.  I have no idea how so much of the metal was worn off as it was on the spindle encoder the only idea I had was metal chips getting in between the belt.  And the pulleys were made of zinc I believe so it wore the tooth down.  No one believed me until I showed them the old pulley and a new old stock pulley I had to compare with.


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