[Surfie]

Hi All,

This is probably a really obvious question but I am after a summary of some general principles to improve the maximum (non cutting) rapid movement of my machine. I.E bigger motors increase the speed. My explorations on the forums haven't really provided a nice summary for me (please correct me if there is already something like this out there).

I am also after specific advice to my machine, the specifications of which are below:

Motors: Nema 23 3Nm
Stepper Drivers: four M542T drivers microstepped at 6400 pulse/rev, set to operate at a peak current of 4.5A and set to half current mode (this seemed to give me the smoothest results)
Power source: four stepper drivers operating off a single S-400-36 (36V, 11A) power supply
Drive: 1605 ballscrews (16mm diameter, 5 mm pitch)
Current max rapid movements: 1320 mm/min (this just seems very slow for rapids, especially if I have to sit there for a minute or more to get it from one end of the table to the other)

Any advice on how to make the max feedrate faster?

Let me know if any other information is required.

Many Thanks

[extent]

Do you really need 0.8 micron per step? That's the first thing I would change to a more sane value just as a mater of course. Reducing your microstepping can help you get more speed if you're running out of steprate between the motion controller and the motor drive, but with a decent motion controller and wiring I wouldn't expect only 28khz step rate to be a big problem for you even at your current settings. Lowering your acceleration can also help you reach higher top speeds as you start running out of torque at higher RPM, if you're losing steps on the motors.

[QuinnSjoblom]

I assume you tried increasing the velocity until losing steps? With 300oz nema 23s and same ballscrews, I'm getting 9000mm/m without ever losing steps. Like mentioned, I would drop down your micro step to like 2000 per rev. That's 2.5 micron per step which is still plenty of resolution. Same as what a tormach runs at.

[ger21]

This is probably a really obvious question but I am after a summary of some general principles to improve the maximum (non cutting) rapid movement of my machine. I.E bigger motors increase the speed.

Bigger motors are often slower, due to higher inductance.

With stepper motors, the faster they spin, the less torque they have. Motors with lower inductance will have more torque at higher speeds. To overcome high inductance, you usually want to run at higher voltages.

If you want to go faster, there are a couple things you can do.
1) Use 10mm (or higher) pitch screws. This lets the motors spin lower, where they have more torque.

2) Increase the voltage. Higher voltage gives more torque at higher speeds.
A general rule is that usable speed is proportional to voltage. Double the voltage, double the speed.

3). Depending on the inductance rating of your motors, switching to a lower inductance motor may give a large increase in speed.

Unfortunately, all of these methods involve replacing components.

[Surfie]

I tried several different microsteps but this one seemed to be the smoothest. I will try decreasing the microsteps. Interesting about the acceleration. I hadn't thought of that...

[Surfie]

Interesting what your saying about higher voltage implying higher speeds.... from memory a higher voltage implies a lower current which implies less force to turn the motor.

[QuinnSjoblom]

Interesting what your saying about higher voltage implying higher speeds.... from memory a higher voltage implies a lower current which implies less force to turn the motor.

Higher voltage will definitely increase your speed capability, as with any motor.

As for the acceleration, it just depends at what point you're losing steps. If your acceleration is set too high, the stepper has to work harder to get the mass moving in less time, which can make it more likely to lose steps.

Can you explain in a little more detail what happens when you increase the velocity? Do you just lose a single step every once in a while? Or does the stepper suddenly start losing massive amounts of steps on every move? And you are losing steps right? You made no mention of it in your original post. You just said you couldn't get higher than a specific rapid speed. Just want to make sure you understand that your rapid speed is determined by the max velocity set in the software. You can set it as high as you want up until the point of losing steps.

[dharmic]

Interesting what your saying about higher voltage implying higher speeds.... from memory a higher voltage implies a lower current which implies less force to turn the motor.

Higher voltage will only mean lower current for the same power. For what you're seeing in a motor, higher voltage will push more current through the motor, use more power and create more heat.