Driver & Driven

Hi

I should know the answer to this, and i think i do, i just need reassuring.

I have a 3Nm, Nema 23 motor, i am going to use to power my Z axis on my milling machine, i intend to use a toothed belt & pulleys, my question is this, should the DRIVER pully (ie, attached to motor shaft) be LARGER or SMALLER the the pulley being DRIVEN (ie attached to Z axis Leadscrew)

Regards

Ray

Well really that depends on what your after.? If your wanting higher speeds then larger pulley on driver, this will come at the cost of torque.
If have a fast motor and are wanting slower speeds with more torque then smaller on the driver.

I think you'll be looking to increase torque so go small on driver.

It all depends what gear ratios you want to achieve. Generally speaking, a direct drive system would use either Oldham Couplings or drive pulleys of the same diameter. For increased torque and slower speed, you need to use a smaller pulley on the motor (or a larger pulley on the leadscrew).

Incidentally, notice I linked to HTD5 pulleys above? I bought T5 pulleys and then discovered the belts are pretty expensive. The HTD5 pulleys are (apparently) a better choice as they will have less backlash and are easier/cheaper to get hold of.

Hi again

My X & Y axis are direct drive, using Oldham Couplings, the Milling head, gearbox & motor are quiet heavy, i am not to bothered how fast the Z axis travels, i am more interested in relieving some work on the motor, thats why i thought of using timing belt instead of direct drive, should i use 2:1 or 3:1 Should this be Driver to Driven or Driven to Driver?

Regards

Ray

I'd go 3:1 with small pulley on stepper.

If you want to relieve some stress on the motor then use some form of counter balance, either weights or gas struts.

Hi All

Again many thanks, believe it or not, that's just what i was thinking of, honest, just had one of those age moments that lasted a couple of hours.

Ray

I have pulleys for 3:1 on my Z-axis as well!

However, this interesting response was a reply when I asked the very same question: http://www.mycncuk.com/forums/faqs-p...html#post47446

Thanks Birchy.

I had already decided on a key way driven pulley on the Z axis Leadscrew, has the existing shaft has one in, so i will utilise the existing keyway.

Regards

Ray