motor speed

[thestruuus]

I just completed my cnc machine and I have a motor stalling problem. When I run at 30IPM all the motors are fine, but if I increase the speed to greater than 35 the motor accellerates up and stalls until it slows down. At 3600 steps/in 30 IPM comes out to 540 RPM. I am told that 30IPM is a very slow speed. Is that a slow IPM also do you know what a typical stepper can rotate in RPM?

[ger21]

Originally Posted by thestruuus I am told that 30IPM is a very slow speed. Is that a slow IPM also do you know what a typical stepper can rotate in RPM?

Yes, 30ipm is quite slow. However, 540rpm is not too bad. There really is no typical stepper speed. Speed is basically proportional to the supplied voltage. Double the voltage, you double the top speed. Up to a point. Over 20x the motors rated voltage and the motor will get too hot. Most hobby priced drives are limited in rpm by their lower max voltages. To compensate for lack of rpm, you want to use a leadscrew with fewer turns per inch to get more speed at lower motor rpm, where the motor has much more torque.

What type of screws, motors and drives are you using? And at what voltage are you running them at? Looks like 20 turn per inch screws?

[thestruuus]

They are 5/16-18 threaded rod. so 18TPI. They are 24v steppers. The driver has fractional step sizes avalible, right now they are set to full step. If I run at a fractional step I have to increase the SPI, so I assume that step size = 1 would give me the least control but max speed... I'm at a loss.

[ger21]

I'm assuming your steppers are not 24V, but you're using a 24V power supply. What kind of drives are you using?

Microstepping should make the motors run smoother, and you may get a little more speed, but unless you can increase the voltage, you probably won't get much more speed. You're best bet would be to change to acme screws, something around 4-5 turns per inch.

[.xXACEXx.]

if every thing would run the same,even moving to 1/2 x 13 screw would give you an increase of about 11.5 inches a minute (41.5 ipm) but yeah acme would greatly increase the top speed if motors and drives can handle the load ill admit i dont know alot about the drives...but mechanically..consider if you could put a 1 turn per foot lead screw on the same machine with no added stress..(and belive me there would be added stress )if your running 540 rpm and getting 30 ipm..at one turn per foot you would be getting 6480 ipm!!! now that (altho impossable) would be fast...