Stepper Motor Question

Just disregard the last two comments, and you'll be fine Bill ;)
 
No, I won't I'm afraid. I am going to modify a mechanical unit to fit my lathe. I will have to redesign the carriage somewhat but this is what I do and what I am good at. You all for the most part have been patient with me and I appreciate that.

"Billy G"
 
Thank you for the offer . but I'm afraid that electric is out of the question. As before when this was brought up everything was OK then someone says it's not OK. Someday CNC things will become an equal opportunity for everyone. Mechanical is straight forward.

"Billy G"
 
awander said:
Just a bit of a quibble-the stepper motor is not "bipolar" or "unipolar"-the linked motor is an 8-wire motor and that means it is about as versatile as a 2-phase stepper can be. It can be run from a unipolar drive, or it can be run from a bipolar drive in series, parallel, or half-winding modes.

The Linistepper is a unipolar drive, and it would work fine with this 8-wire stepper motor.

A 4-wire motor would not be capable of unipolar operation, but any 6- or 8-wire 2-phase stepper can be driven by either a unipolar or a bipolar drive.

I know the OP stated the motor was "bipolar", but that is incorrect. And the question itself was not really a good one, "What kind of stepper motor is it? (Bipolar, Unipolar, 3-phase, etc.)". I think a better question would have been "What kind of stepper motor is it (how many wires, how many phases)".

It looks like a pretty nice motor, BTW,

Andy Wander
Click to expand...


You're mostly right. Bill's motor can be run as you state. But, there is a difference between dedicated unipolar and dedicated bipolar motors motors internally. A unipolar is wound a bit differently to maximize the torque you can get with only one of the four "phases" energized. In addition, unipolar driven motors generally microstep poorly. In other words, there's a discontinuity in the position as the commutation sequence crosses through the motor's inhernent detent.

Bill's motor can indeed be run as as a unipolar, but he would get significantly less torque (usually 50% of the bipolar torque, but could be 70.7% if commutated differently).

Electrically, a unipolar motor is like a bipolar motor with a center tap brought out of each of the two active phases. So what do we have: unipolar=ease of commuation, less torque per unit size (K sub m), bipolar=harder to commutate (more circuitry required), better suited for microstepping, more torque per unit size.

John
 
If you're talking about a regular DC gear motor, I think you'll be happier with that anyway. The controls are simpler, and they are analog, so you should get smoother output. I have some motors that were intended for a power windows in a car, and they would work fine for this. Another option is a cordless electric drill. Once the batteries go, people are eager to get rid of them. They have powerful motors, a decent gear train, and a built in speed controller.

Incidentally, this is exactly the setup that hardinge uses on their toolroom lathe; power feed (not threading) is controlled by a DC gear motor. Never used one, but supposedly it works fabulously.
 
DMS is right. Using a DC gearmotor with an output torque rated as described earlier, will work exceptionally well. Raiding a cordless drill for parts could be good idea.

John
 
:agreed:

A DC motor with a gearhead would be much simpler for your application Bill. Rather than a "cheap" DC supply though, I would suggest using a pulse width modulated (PWM) supply (still inexpensive). They pulse full power to the motor and generate a lot more torque than just varying the voltage to control speed. Power feeds use PWM supplies, which is why you can feel them pulse at slow speeds.

Herbach & Rademan is an excellent source for DC motors and I believe they have PWM supplies as well.

Here's a PWM supply with reverse for $10. It's only 10 amps, but larger ones are available.

Tom
 
TomG said:
:agreed:

A DC motor with a gearhead would be much simpler for your application Bill. Rather than a "cheap" DC supply though, I would suggest using a pulse width modulated (PWM) supply (still inexpensive). They pulse full power to the motor and generate a lot more torque than just varying the voltage to control speed. Power feeds use PWM supplies, which is why you can feel them pulse at slow speeds.

Herbach & Rademan is an excellent source for DC motors and I believe they have PWM supplies as well.

Here's a PWM supply with reverse for $10. It's only 10 amps, but larger ones are available.

Tom
Click to expand...

arn't most milling table power feeds made this way?

Does have a lot of advantages of simplicity. Combined with a high reduction geat box you could achive some good torque.

Stuart
 
TomG said:
:agreed:

A DC motor with a gearhead would be much simpler for your application Bill. Rather than a "cheap" DC supply though, I would suggest using a pulse width modulated (PWM) supply (still inexpensive). They pulse full power to the motor and generate a lot more torque than just varying the voltage to control speed. Power feeds use PWM supplies, which is why you can feel them pulse at slow speeds.

Herbach & Rademan is an excellent source for DC motors and I believe they have PWM supplies as well.

Here's a PWM supply with reverse for $10. It's only 10 amps, but larger ones are available.

Tom
Click to expand...

A PWM driver is ideal! I wasn't aware they made them that inexpensively... But, now that I think about it, it makes sense.

Sounds like you've got your answer Bill: A DC gearmotor and a PWM driver. Doesn't get much simpler than that. All you need is a 12-40V source.

John
 
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