Re: [CAD_CAM_EDM_DRO] Timing Belt Sizing

Hugh Currin wrote:

> I'm retrofitting a Bridgeport copy for X & Y CNC. I'm using
> 785 oz-in steppers with 5A stepper drivers from Camtronics.
> I plan to connect the steppers to the ballscrews with timing
> belts of 2:1 reduction.
>
> When I run the numbers for a timing belt I find I need a
> 1.0" wide L belt with pulleys of at least 28 teeth and 56
> teeth. This is a driver pulley of 3.3" diam and a driven
> (leadscrew) pulley of 6.6" diam. OR, a 1.0" wide H belt
> of 14 or 16 teeth/28 or 32 teeth. These have diameters of
> about 2.5" and 5.0". The H could be smaller but you run
> into number of teeth in contact problems.

I am using 3/8" wide belts with relatively small sprockets.
I am using about a 10 tooth on the motor, and I guess that would
mean a 25 on the leadscrew. I broke one belt when I had the
acceleration turned up too high, but I have used it for 2 years
with no trouble whatsoever. This is with 1/8 Hp continuous-duty
servo motors, and the servo amps set to deliver about 1000 Lbs
of linear force to the table, maximum. There is something wrong
with your calculations, or you are planning on delivering 10 G
accelerations to 1000 IPM, which I don't recommend on a
Bridgeport.

Jon