[Pinhead]

Any one know/using a set of drivers and motors that can get 150ipm with a .1 pitch lead screw?

I need help finding the right combo for a smallish gantry router.

I cut mostly way and model board on a rotary 4th axis but have been having a hard time finding a stepper combo that will put out 1500rpm while cutting wax or similar light materials.

I have been told that there are some "tricks" in Mach 3 to get this done but I'm not sure what they would be or what the best combo of power/steppers/controller would be to get me there.

Simply looking at the stepper motor specs is not helping, most have a usable power band at up to 40-60% this gets me about 700rpm with most steppers and translates to 70ipm.... So unless I'm overlooking something or have it completely wrong I'm not sure how to get there.

Thanks for your help!

[ger21]

Mariss from Gecko posted yesterday that you should be able to get close to that with a Gecko G540, at 50V, and a ~200oz stepper rated at 3-3.5amps. Not sure what thread it was in, though.

[Pinhead]

Thanks Ger21 I'll start searching....

[jeffs555]

What diameter and length of lead screw are you using? Depending on length, diameter, and bearings you may not be able to do 1500rpm without whipping.

[Harley2003]

I was wondering if you could add a gearbox or a belt and pully system to increase your leadscrew rpm. If you added a 2:1 system you could keep the motor rpm where you want it to be and double the rpm of the screw.

Not sure if the motor you have will drive the machine at 2:1 but just a thought.

Good luck with the unit.

[irving2008]

How long is the leadscrew? You say smallish...assuming a 2' long screw of 1/2-10tpi it will need to be supported both ends in a simple bearing, that gives a critical speed of 2700rpm which is above the 1500rpm you need (to avoid whipping).

To overcome the inertia of that screw which is the primary load and achieve a reasonable acceleration to maintain accurate cuts you'll need 32W of motor power, which is roughly 0.2Nm or 28oz-in of torque at that speed (which equates to 5000 full-steps a second)

looking at a typical 3Nm motor, eg SY60STH88-3008BF, you can easily achieve this torque at 5000pps using 4.3A and 40V, so 3,5A and 40V drivers should do the trick. For this very high pulse rate you want the lowest inductance motor you can find (the one suggested is 3.2mH which is good, 2.5mH would be better).

The problem with gearing down as suggested is increased inertia... gearing down is fine for rapids but you need the acceleration at that speed for accurate cutting. Really you want to look at a higher pitch screw, say 4tpi, but that will need a bigger diameter screw (therefore more inertia, bigger motor), or a much better option is a multi-start leadscrew. A 4 start screw would improve things by a factor of 4.