Quote Originally Posted by Robin Hewitt View Post
Is a 10 tooth pulley big enough to hold the belt on a quarter turn? That's 2 teeth.

Is it small enough to get any kind of resolution on a stepper?

A 15mm PCD pulley moves it 47mm per rev.

0.12 mm/step before you start springy microstepping, will that work for cutting alloy?

If you microstep can you rattle the PUL pin on the driver fast enough to get the top speed?

If you gear it down, do you move beyond the top speed of the motor?

Beginners don't usually play with the numbers, they just look for massive torque motors and hope that will make it right. That's why steppers are usually sold by the Newton meter rather than by the torque to speed graph.

130kg belt tension may exceed the permitted side loading on the motor shaft.

Can you actually get a big enough shaft inside a 15mm aluminium pulley without severely under cutting the teeth? I think you will need a bearing either side of it.

A little maths and understanding to find the best compromise before you build can save a lot of disappointment later. (Please assume a big grin smiley, the new editor restricts my smiley selection, sometimes it shows, sometimes it doesn't).
hi robin
looks like i will need to go back to school,maths was never my strongest subject
i was thinking more along the lines of a 40mm pulley!!!.and driving the stepper with a reduction to the shaft.would this work or would the stepper be running to fast when the ganty is moving at high speed
as you have said i am just a beginner and speed,torque,force applied etc are all new to me.
i was thinking of making a prototype using chains and sprockets (my works got plenty)just to try out the theory,measuring pull needed to turn drive shaft with spring scales!!
thanks for your input
Tom