timing pulleys

I solved my problem with timing pulleys with the help of Gates Canada and
the local Gates warehouse. One of the interesting things I found out was
that Gates is getting out of many of their aluminum pulleys due to the new
belts being so strong and hard, they are causing wear on the aluminum
pulleys. This is a double edged sword for CNC, positive cause you can use
smaller pulleys, but negative because steel pulleys are much heavier.

So, my question would be... how would a person calculate the momentum of
steel pulleys in order to appropriately size your servos? Is there an
article which deals with this? Seems to me the increased weight would be a
lot of rotational momentum added to the servos for acceleration and
deceleration.

By the way - locally the smallest GT2 belts available are 8mm. The smaller
ones aren't carried in our area because of the heavy oilfield
industry. They have to be ordered in from Kentucky... a 3 week
wait. Since I have friends and acquaintances planning on building CNC
machines, it seems advisable to use what we can get locally, hence my
questions.

Another option would be to lighten the pulleys by drilling holes or
machining some material out of them. The problem then is balance. How
critical is balance on an NC with say 2000rpm max servo speed? Is there an
easy way to balance the pulleys?

Rod


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