Re: [CAD_CAM_EDM_DRO] Belts & Pulleys

Hi Jason,

Yes, there will always be a small amount of backlash in a belt drive
system. Visualise a very loose belt, as it changes direction, there
will be some rotation of the motor pulley with no rotation of the
following pulley until the belt slack is taken up in the opposite
direction. Now visualise the belt with very high tension. Backlash is
dramatically reduced, but belt wear and probably efficiency will suffer.

The best belt design guide I have found is the SDI guide at
http://www.sdp-si.com/D260/D260cat.htm It talks about the different
profiles etc. In the given application on page T9, the amount of
backlash for two 20 groove pulleys with 6.6lb belt tension is about
.012" for a 3mm GT belt and .029" for a 3mm HTD belt. Sounds like a
lot! Backlash is worst at the maximum torque load so typical backlash
numbers should be typically much lower.

In any event, I'm still planning to use a 5mm tooth pitch belt
preferably with a GT tooth profile as this will minimise backlash in my
design.

Cheers, Peter

Jason Cox wrote:

> Hello,
>
> Do belt & pulley drives introduce backlach into a cnc setup? After

looking at many belt/pulley sites I have noticed they quote their
products to be low backlash, how low is low?

>
> Thankyou.
>
> Jason Cox
>
>
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