A CNC Milling Project using the LinuxCNC software and Nema 34 Stepper Motors
After a while of testing speeds with both software stepping and hardware stepping, I have come to the conclusion that hardware stepping is way faster than software.
I now realize that software stepping just won't cut it in regards to speed. I go into further detail here, but basically, the kernel cannot generate enough steps to move the motor any faster.
Using software stepping, my stepper motor moves at 674.9 ipm. To put it in perspective, 674.9 ipm -- in terms of rate -- translates into 285.7 mm/s. If I were to have a 1000 x 1000 mm bed (which is what I am going for) and use this speed, it would take my machine about 3 seconds to go from one side to the other, at its FASTEST.
The jobs would take way too long to complete at this rate. Hardware stepping, however, is different.
Using hardware stepping, my stepper motor (theoretically) moves at 7086.6 ipm . This here is a serious improvement and will ensure that my jobs get finished quicker.
There are more details here at my blogpost.
That's all for now.
So I was doing some calculations regarding my mill's speed, and I figured I needed to calculate the "theoretical speed limit" of my motors.
First, I needed to figure out the maximum rpm of my motor. For this, I needed to figure out the amount of hertz my stepper driver gave off and the pulses per rotation for my motor.
Hertz are pulses per second (pps) , so dividing the pulses per rotation (ppr) by the pulses per second (pps) should give us the rotations per second (rps).
Max Speed = (pps) / (ppr) * (micro-steps)
= 300,000 pps / 200 ppr * 1
= 1,500 rps
1,500 rps is the maximum speed of my motor. However, motor speeds are usually measured in inches per minute (ipm).
Here's how I converted it:
1,500 rps * 60 secs = 90,000 rpm (Converting seconds to minutes)
90,000 rpm * 5mm = 450,00 mm/min (Converting rpm to millimeter per minute)
450,000 mm/min / 25.4 mm = 17,716.5 ipm (Converting millimeters per minute to inches per minute)
Theoretically, that would give me about 17,716.5 ipm on my CNC machine.