Advice: Timing Pulleys and Belts

[Robin Hewitt]

Hmmm...

1:1 on to a 5mm pitch gives you a mechanical advantage of 1256:1

So 3Nm gives a driving force of 3 x 1256 = 3768 N

Question is, do you really need 0.37 tons to drive your Z? Using a 16mm screw suggests you are not lifting the bed.

Is it too late to change motors? I suspect you are severely limiting your top speed.

If you geared it 5:4 then it would half step .01 mm and quarter step at 5 microns which is my favourite, being the resolution of my digi calipers.

[Jonathan]

Hmmm...

1:1 on to a 5mm pitch gives you a mechanical advantage of 1256:1

So 3Nm gives a driving force of 3 x 1256 = 3768 N

Except when the motor is actually spinning, and below the corner speed the torque is about 2Nm, so it's more like F=2*2*pi*0.9/0.005=2262N
Still doesn't change your conclusion - he's not short of force.

On my Z-axis I ended up using 42:22 pulleys since at the time I got a box of pulleys cheap on eBay so thought I'd experiment to see which was fastest...That means my Z-axis can do about 8-10m/min, which given that I'm almost exclusively cutting parts that are <25mm thick, isn't necessary.
I reckon it's more important to maintain resolution and high acceleration.

Is it too late to change motors? I suspect you are severely limiting your top speed.

Pretty sure he's already got it as this is an upgrade to the existing machine.

[Robin Hewitt]

the torque is about 2Nm, so it's more like F=2*2*pi*0.9/0.005=2262N

Where did that 0.9 come from? Is it a fiddle factor?

[Jonathan]

Where did that 0.9 come from? Is it a fiddle factor?

Approximate efficiency of the ballscrew, when Mad Prof. gets one...