Timing belts for x and y axes (what pitch?)

[dowling177]

I am building a CNC router table to cut 3/4" plywood. I am looking into getting a belt that is an 1" wide and has a pitch of 3/8" (is this pitch too big)?

also what are normal prices for these belts I might be paying approx $85 CAN for a 10ft length

Thanks for the input

[Moondog]

Hey Dowling...

Plywood... for boats?.. from the lenght of the belt.. I assume it's for the X Axis.... how are you driving it?...

Pitch... you wouldn't want anything less than 10mm. $85.00 sounds reasonable. Maybe a T10 or a T5.

3/8 pitch?... suitable?.. depends on the size of your pulleys... on a large pulley... 300mm +.. that would be fine... you need to ensure that there are sufficient teeth on the pulley when mounted... there is a formulae.. can't remeber... something like 40% of the teeth engaged?.... if your pulley is too small for the belt then the teeth won't engae properly.. when you use smaller pulleys like on the Z axis a good pitch is 5mm...

hope that helps

cheers

[MrBean]

I used a 1 inch wide belt, 5mm pitch, for my X axis. The belt rides on 26T pulleys. It is geared down 3.6:1 at the motor.

This gives a resolution of:

5mm*26t = 130
1mm/130 = 0.0077

motor is 200 step and gearing 3.6:1 so:

0.0077*200steps = 1.54
1.54*3.6 = 5.544 motor steps to move 1mm

1/5.544 = 0.18mm is the minimum movement. Or .007"

When I build my all belt drive machine I'll use smaller pulleys on the movement belt to give more resolution. And aim for a 4:1 reduction also for more resolution.

Speed is no problem. My 110 OZ motors are running at 65% of rated current and I'm getting rapids of 800 IPM. So can afford to trade off some speed for extra resolution.


I hope that helps you make your choice of what pitch and pulleys to go with.

Regards Terry.....
http://www.terry-is.f2s.com/