cryoscum wrote:Hi PK
I understand that tooth belts are somewhat less tension sensitive than regular drive belts,
Yes, you can run them much tighter. Loose belts give errors and backlash.
I intend to get 2m of the 10mm tooth belt, join the correct length and see what tension it'll have with the current configuration.
Timing belts come in fixed lengths because they are manufactured as a tube with a continuous winding of steel or kevlar around the outside. The manufacturers then slice the tube (like cutting sausage) to give the correct belt width.. 5mm might be just enough.
Any suggestions for the pulleys? Both the same size, maybe about 25mm dia? No need for gear ratios here I would assume?
Get T5 (5mm pitch) belts and pulleys, 10mm width for the cross slide and 15mm for the long travel.
I'd go for 25mm on the cross slide and 30mm for the long travel, just to make sure you get enough wrap.
The belt manufacturers usually have calculators and tables for required width and wrap as a function of torque.
Re gearing. You might want to consider gearing the motors up, ie having the screws turn faster than the motors. This will give you more top end speed and won't make any significant difference to cutting force. Remember that Stepper motors are (by and large) constant power devices. So halving the speed of the motor doubles the available torque. If you gear that motor up by a factor of 2 then the axis will move twice as fast.
It's for this reason, most stepper motor driven machines run with very coarse pitch screws (like 10 or 20mm pitch)
here's a video of my little router showing the difference in speed as a result of replacing 5mm pitch drive screws with 20mm pitch screws. The motors and drives remained the same:
