[jouellet]

Hey folks !

I need to drive a NEMA34 stepper motor, and so far, all the drivers that I have found, requires 400 pulse per revolution (Micro-step = 2). Why is that so ?

I need a model that would be direct, that is 200 pulses per revolution.

Anyone has a seller/model to recommend ?

Jasmin

[Jim Dawson]

Normally steppers are run at 1/2 step or less, I normally run them at 10 micro step or 2000 PPR. You have an application that requires 200 PPR?

[jouellet]

that's because I already bought the motor and Power supply. Motor flange has been machined, and then we realised that the max speed, is not fast enough.

Application is not so much about using the ability to do positioning, but rather the torque along the full speed range.

so if I could use only 200 PPR rather than 400 PPR, I would fall within the acceptable range.

[Jim Dawson]

Automation Direct sells 200 step drives. https://www.automationdirect.com/adc...ives_-z-_Power

[ger21]

Unless you are limited by the pulse rate, I wouldn't expect much difference in speed between full steps and microstepping.

Drives like the Gecko G201X have a technique called step morphing, where they actually run the motors at full steps at higher speeds.

[jouellet]

Gerry,

Correct me if I'm wrong, but if I'm using 1/2 steps, it means I must "send" 400 pulses for a complete rotation. If I want, let's say obtain 400 RPM, it means I must send 160K pulse/minute.

If the driver needs only 200 PPR, my 400 RPM will be achieve with only 80K pulses/minute.

Pulses can only be sent at a certain frequency, dictated by inductance, voltage, etc ... Right now, I'm reaching that limit, so that's why I was hoping to get the same RPM, at half the step count !

Make sense ???

Jasmin

[KOC62]

You can also increase the stepper motor speed by increasing the power supply voltage. Take a look at this primer; https://www.geckodrive.com/support.html

[ger21]

What are you controlling the motor with, or what's generating the steps? 160K steps/min is quite slow. I'm sending 150K steps/second to my motor.

[KOC62]

If one is using Mach 3 with a kernel speed of 25KHZ then you can't exceed 25000 steps per second, right? Unless you get a license and have around 100KHZ kernel rate - if the PC hardware permits.
You will need to use an external hardware device similar to a "Smoothstepper" to get a higher step rate.

[ger21]

He's worried about 160,000 steps /minute. At 25Khz, you can get 1.5 million steps/min from a parallel port.
And on most PC's, you can get 45-60Khz from the parallel port with Mach3.

[jouellet]

The controller is an Arduino. All it does, is FWD/REV, with the speed being controlled by the reading of a potentiometer's value.

The principle is extremely simple: it controls a rotating mechanism, where the speed is controlled by a foot pedal. The whole skid allow a welder to control the rotation of a big pipe (24-36") while he's welder a joint. Right now, he can weld a bit faster than the max speed that I can achieve.

There is a gear box involved. The main reason I picked a stepper motor, was because of the great torque at low speed, and also because is is fairly cheap.

Found a stepper driver, NEMA34 rated, that seems to do 1:1 step. I will see when it gets here...

Also ordered a 60V power supply, to replace the 48V one, hoping to gets those extra RPMs that I'm missing !

[jfong]

If this is a Custom Arduino program, make sure you are using acceleration/deceleration when commanding the driver/motor. Large motors don’t like instantaneous movement without a ramp up in stepper pulses.

This library will do that for you. The Arduino is good for atleast 25,000 steps per second with good programming (grbl firmware). It should not be a limiting factor on your max motor rpm when using a full or half step driver.


Max motor rpm is due to motor inductance, power supply voltage used and driver quality. The faster the motor spins, the less torque is available. You may be reaching a point where there is not enough torque and the motor will mis step and lose position. What model stepper motor are you using? Try to find a rpm vs torque curve for you motor.

AccelStepper: AccelStepper library for Arduino


Edit

The AccelStepper is only good for 4000 steps/second or 240,000steps/min. I thought it was faster...,,

For a full step drive, max rpm achievable is 1200rpm.
Half step drive would be 600rpm

There are other Arduino stepper libraries that may go faster. This assumes your motor can even spin 1200 rpm!!

[KOC62]

He's worried about 160,000 steps /minute. At 25Khz, you can get 1.5 million steps/min from a parallel port.
And on most PC's, you can get 45-60Khz from the parallel port with Mach3.

Ahh... just noticed the 160K/min which I was seeing as 160K/sec. My bad...