Hey Iggy - stepper motors ?

On Fri, 30 Jan 2015 06:39:20 -0600, "Lloyd E. Sponenburgh"


Quite often true, but it can also depend on which they have more of: money or time. Lack of time can play heavily into that decision. So can the need (or wish) to learn a machining procedure/method.
I'll buy an HF tool to do a quick one-off job. But if I see that down the line I'll need it quite often, I'll either make a better one (if possible) or buy the better brand-name tool for it. That brings value into the equation, too. Those of us with less money are very familiar with this aspect.
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On Fri, 30 Jan 2015 06:51:47 -0800, Larry Jaques

It doesn't make much sense to turn a hobby into a religion. Those of us who take the "recreational" part seriously should have an easy answer: if you find it pleasurable to do so, then make it. If it's a chore and if the option to buy is reasonable, then buy it.
Like most people here, I've often made things that made no sense to make, and then took a brief pleasure in having done so, for several reasons. Then, if reason slipped into my consciousness at some later point, asking "why in the hell did I do that?," I sigh and swear to think first, the next time, before sucking up precious hours to satisfy some atavistic urge that made as much sense as tailoring my own underwear. d8-)
Or, as we said in the '60s, "If it feels good, do it."
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Yeah, I'll go along with that.
Lloyd
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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> prodded the keyboard

+1
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On Fri, 30 Jan 2015 11:43:57 -0600, "Lloyd E. Sponenburgh"

I've often made something and ended up replacing it with something purchased , even though what I made "worked". Generally I'd have been farther ahead buying the right parts in the first place. Buying "parts" does not preclude building the machine.
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Ed Huntress wrote:

I took great pleasure in the building of both my Holes Creek ball turner for the lathe and my home made boring head for the mill . I get even more pleasure out of using them .
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Um... I didn't say they were. They can be made INTO servos quite easily, and if you have an application that won't mind the inherent backlash in the geartrain, they're quite powerful and quite inexpensive for the torque they'll put out.
Lloyd
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On 2015-01-30, Lloyd E. Sponenburgh <lloydspinsidemindspring.com> wrote:

My own thinking is, if you are smart enought to make a servo out of a wiper motor and adapt it to a milling machine, you should be able to make enough money in less time to simply buy proper equipment.
i
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On Fri, 30 Jan 2015 08:07:40 -0600, Ignoramus8636

Changing a wiper motor into a servo motor only requires a feedback device. An encoder will do. The wiper motor will probably not make a very good servo motor though because there are not many segments in the commutator compared to a motor designed for servo use. Eric
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snipped-for-privacy@whidbey.com fired this volley in

Think "commutator segments per revolution". They're geared WAY down.
Lloyd
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On Fri, 30 Jan 2015 08:07:40 -0600, Ignoramus8636

+2 on that. Decent low cost steppers af reasonable power are readily available at reasonable cost, and stepper drivers are likewize easily available. When you are done you have something that works properly and looks like it will.
To put a decent decoder on a wiper motor takes some hacking. Do you put the encoder on the motor shaft, or on the output gear? On the motor shaft gives much higher resolution, but requires a lot more hacking (physically) to get to the motor shaft. - and then it is all exposed unless you build a housing for it. Or are you talking about a circuit to determine the revolutions by reading the waveform from commutation? If so, even the big manufacturers can't seem to make THAT work reliably..
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snipped-for-privacy@snyder.on.ca prodded the keyboard

No just take the output from the DRO scale.
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wrote:

I'd rather just punch in a number - from this point go 100,231 counts, knowing 10 counts is 1 thou, or whatever, and the control does the rest. And you can program the feed speed by adding a delay loop between steps on the stepper. Just using a PWM the motor slows dwn under load so you could get a variable speed feed, which could affect the look of the finish.
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    [ ... ]

    Depends. If you make it a *real* servo, there should be some form of speed feedback, so the PWM is automatically adjusted to maintain the desired speed.
    A *real* servo motor has a tach generator on the shaft as well, so this is easy to do.
    If you've just got an encoder, you need to integrate the pulse rate from the encoder to derive a speed value, and tuning it is a bit trickier.
    Enjoy,         DoN.
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wrote:

Standard modern found that out, in spades, on their NC lathes. They attempted to use integrators to control the "servos" for the X and Y axis, and repeatability was terrible. After Standard Modern gave up on the lathe I spent hours on it getting it useable (sort of, anyway)- we changed grounds and sheilding, and put the PC on a dual conversion UPS (separately derived power source) and got the failure rate down from over 30% to less than 3% on production runs of 600 parts. It was the most useless damned piece of equipment I ever had the msfortune of running across, My buddy Steve lost his shirt on it - this was back at the time that Standard Modern failed and before LeBlond took it over.

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On Fri, 30 Jan 2015 06:38:20 -0600, "Lloyd E. Sponenburgh"

Well, he said "wiper motor" and you said "servo", so it was implied/inferred.

Aren't most power runs usually just removing background field material? I would think that backlash wouldn't matter for many runs, though I don't see where backlash would come into it during a run. It would have constant feed, right, with limiters cutting off power at the end of the run?
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On 29/01/15 14:46, Baron wrote:

One issue with typical wiper motors is they're only intended to rotate in one direction and in my experience don't run as well in the reverse direction. The few I have taken apart only have thrust provision for the intended direction. I have used them to run in both direction and it worked OK. Window winder motors are bidirectional and have thrust pads at both end of the shaft on the ones I've dismantled.
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David Billington prodded the keyboard

Yes that's true ! Which is one reason that I used a tumbler gear mechanism to reverse the table direction. Limit switches take care of running into the ends of the table.
As far as servoing is concerned, isn't that what the DRO is for. Set zero and run to value "X" then stop.
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email.me:

Yup. The term "feedback" covers a lot of ground.
Lloyd
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On Fri, 30 Jan 2015 15:37:54 -0600, "Lloyd E. Sponenburgh"

If you are using it for "full stroke" milling I guess a wiper motor is useable. Certainly not if you are going to try to set it up as CNC - which is more what I was thinking of when you mentioned power driving the feed.
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