Issues with a stepper motor drive

with out seeing the stepper driving circuit, it could be a lot of things. is the stepper motor spec'ed out to operate at the desired RPM?

Is this driver circuit something you made? if so, have you scoped out the actual signals ? etc.. we need a little detail on the circuit driving the stepper motor.

P.S. Steppers are generally not suited for high speed applications.

if you need indexing, maybe what you should do is use a DC motor with some torque and a A/B,Z feed back encoder into a uC or a PLC..

Like I said, I don't know your application. maybe you could spill a little more on the actual electronics here.

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Try an elastic/spring coupling at the motor to the box? Something that will add just a bit of looseness to the system. Steppers aren't their best at high speed and under load (starting torque). If you want to operate a positive displacement pump, for instance, you either have to add some black magic to the coupling system or grossly increase the size of the stepper, or both.

High speed of only 15 RPM? At the stepper, or the output of the gear box?

Too much friction in the system will also cause both problems.

DC servo is the obvious choice for that application unless it is expected to be essentially stalled just supplying pressure to a system without moving.

Steppers can be hard to apply for high starting torques. The elastic coupling lets the motor get to the next step while the drive pulse is still there, and then returns energy back to the system while the mechanical gears catch up.

Mechanical resonance's are something else to look out for . . .

chetanthegreat wrote in news:badaae5a-4f32- snipped-for-privacy@e10g2000prf.googlegroups.com:

do you really mean 400kg/cm? that's about 5500psi. That's scary pressure. This must be a massive structure.

What's the stepper torque rating, whats the rated Amps and volts for the stepper, do you have a manufacturers torque curves?

What's the lead of the leadscrew, what's the area of the piston or working surface in the cylinder operated by the leadscrew. Do some math - almost certainly the stepper doesn't have the power to produce the pressure you're expecting, so it's stalling.

If the stepper 'slips' at 15rpm with no load that's another issue. A Steppers 'high' speed can be 1000rpm or more, depending on the load. If it's slipping at such a slow speed then you have driver issues. You need to show us what drivers or schematics you're using.

What voltage are you supplying and at what current.? Steppers should be current limited to thier plate rating but voltages from the driver can and often should be up to ~20 times the rated voltage - *as long as the driver is a current limiting device*. Without the high voltages the stepper will not achive reasonable speeds or much power either.

Not necessarily. There's something called High Performance Liquid Chromatography pump used in chemical compound analysis. A pump with a sapphire/ruby piston supplies milliliters per hour at pressures from

1-10K PSI. Sits on a table and occupies a half cubic foot or less. Just a little flow, at high pressure, through 1/16" SS tubing with a .02" bore . . .

You are thinking in pounds per square inch and imagining lots of those square inches - when the tubing is very small even plastic will work.

Not scary at all. It fails and the usual symptom is a dribble of liquid. Liquid under pressure is actually a lot nicer than steam or gas when it fails (as a general rule - there are exceptions).

My first guess was HPLC when he said stepper and pressure . . . Chemists are always looking for a pump that won't cause pressure pulses. One way is to just load a large thick cylinder with liquid (lots of square inches) and just slowly squeeze it out at a ml/hr rate

- no pulses since there's only one stroke of the pump.

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