how to control shrinkage of rib belts

[daleammons]

Our reject rate is realy killing our abilty to fill orders we seem to be unable to control the center distance on our rib belts after curring and grinding. We throw away 5000 belt a month. Im looking for ways to control shrinkage of rubber belts.we already have a climate controlled room whereour belts are kep for 24 hours and a whole lot fail.WHY

 

[patprimmer]

The shrinkage will most likely be in the reinforcing yarn.

It could be down to several factors:-

1) Variations in curing temperature of the rubber.
2) Variations in tension when weaving.
3) Quality or grade of the yarn used. You can test the yarn by annealing it and seeing if you get the same shrinkage from batch to batch, or supplier to supplier or whatever else might be a variable. Some yarn manufacturers offer what they call high efficiency yarns and some offer low shrinkage yarns. The low shrinkage are stretched then annealed or relaxed to minimise shrinkage and the high efficiency are stretched and annealed to give the highest strength in the finished product rather than the highest test results for the yarn as a single thread before weaving or further processing.
4) Change of polymer in the yarn, like from nylon 6 to nylon 6.6 or to PET for instance.
5) Variations in tension when curing the rubber.



Regards

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