Re: [CAD_CAM_EDM_DRO] Re: Stepper Dissasembly

> Hi,
>
> I understand your point of view, but I have to deal with situations
> when "junk goes wrong".
>
> I had someone (no one on this group) that hooked up and destroyed 6
> drives in succession on a motor he had liberated from a dumpster. I
> had him send me the offending motor and it had a shorted turn on one
> phase. An ohmmeter wouldn't show it but an inductance bridge did.
>

Ouch! Still, shorted turn or not, the chopper shouldn't put more
current through the winding than it is programmed to, should it?

You do have an excellent point about ohm meters. Mine is useless for
low-resistance stepper coils. I found though that an analog voltmeter
put across a running chopper output can help identify relative winding
resistance, as the average voltage is lower for lower resistances.
This helped me figure out the wiring a of 6 wire stepper the other day.

As for dissasembling motors, if the rotor gets damaged by breaking the
magnetic circuit, then one might be able to slide it from the motor
into a tight fitting soft iron sleeve, then back. Sounds tricky, but
about as complicated in reality as transferring a ballnut between a
mandrel and a screw.

I agree though that a 'free' motor must be weighed against the time
invested and the risk to other equipment.

Chris

> One "free" motor and six dead drives.
>
> Mariss
>
> --- In CAD_CAM_EDM_DRO@y..., "Art Fenerty" <fenerty@h...> wrote:
> > Hi:
> >
> > Just my two cents worth...Never listen when someone tells you
> something is
> > junk. I have dissassembled and fixed just about anything including
> countless
> > items that are "Do not take apart. It will never reassemble" able.
> I have
> > taken apart dozens of stepper motors, reassembled, and run them for
> lengthy
> > periods of time with no noticeable problem. Its the same thing with
> rewiring
> > the SloSyns, some folks said, they will never work, you'll only get
> one RPM,
> > You'd need 400VDC, the formula's prove.....etc.
> > I just sit and watch them work great and smile.
> > The only rules in hacking something together is...there are no
> rules. If it
> > works, it works, if it don't, you learn something. Just don't let
> the smoke
> > out, its hard to buy surplus smoke to replace it with.
> >
> > Art
>
>
>
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--
Christopher C. Stratton, stratton@...
Instrument Maker, Horn Player & Engineer
22 Adrian Street, Somerville, MA 02143
http://www.mdc.net/~stratton
NEW PHONE NUMBER: (617) 628-1062 home, 253-2606 MIT