Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!dayton!jad
From: jad@dayton.UUCP (J. Deters)
Newsgroups: sci.electronics
Subject: Re: Stepper Motor
Message-ID: <6619@dayton.UUCP>
Date: 20 Jun 89 16:20:23 GMT
References: <7137@cbnews.ATT.COM> <1137@cbnewsc.ATT.COM> <19588@cup.portal.com> <3242@kitty.UUCP>
Reply-To: jad@dayton.UUCP (J. Deters)
Distribution: usa
Organization: Terrapin Transit Authority
Lines: 30

In article <3242@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes:
>In article <19588@cup.portal.com>, mmm@cup.portal.com (Mark Robert Thorson) writes:
>> BTW.2, a friend of mine who is a machinist doesn't know how steppers and 
>> servos work, but he sure knows which ones he likes.  He says steppers are
>> crap.  Eventually they go bad, while servos last forever.  His exposure
>> to motion control systems comes from CNC (computerized numerical control)
>> systems used to run machine tools.
[ net.bandwidth saved by deleting much of argument, thereby pleasing the
  net.cabal* ]
>> I suppose the mechanism of failure is
>> the gradual de-magnetization of the magnets in the step motors.

The typical failure mode is bearing failure.  Most servo motors are used
in spindle applications whereas most stepper motors are used as axis
positioners.  The servo motors are typically running at higher speeds,
then, and the steppers are swinging back and forth.  The frequent
start-and-stop of an axis-controller plays hell with the bearings,
whereas the (relatively) constant and smooth speed of a spindle is
the least damaging to the bearings.

Actually, the most frequent failure I saw on our CNC gear was seal
leakage.  Most coolants used in the newer CNC equipment are water-based.
When the seals fail, _BZZZT_.  (This happened mostly to the turrets.)

-john

* there is no secret cabal.

-- 
"Captain's log:  Stardate 2734.3.  'I am nailed to the hull.'"