Re: [ATM] Voice coil actuators was: DC Motor for grinding machine question

["Don Clement" <don_clement@charter.net>]

Gary,

How are you going to do that?

Don

> Don,
>
> Those devices do look quite powerful (and costly!) - but I'm still
struggling to understand how their motion, or that of a solenoid, (both of
which seem to be linear) would be used to provide the power for something
like a mirror grinding/polishing machine.
>
> Gary Fuchs
>
>
> >
> > The "small" S-Series of Unholtz-Dickie electrodynamic shaker systems
have
> >up to 8.5K lbsf see: http://www.udco.com/sseries.htm
> >
> >"Electrodynamic" is another term for voice coil actuator. The new U-D
shaker
> >amplifiers are 90% efficient air-cooled class D switchers. Did someone
say
> >PWM?
> >
> >
> >
> >
> >
> >Don Clement
> >
> >Running Springs, California
> >
> >
> >
> >>
> >> I am not sure about "voice" coil actuators specifically, but have
> >> seen very powerful selenoids, etc using same basic physics. I am
> >> very confident such devices could be used.
> >>
> >> Dominic
> >>
> >> On Mon, 20 Nov 2006, GARY FUCHS wrote:
> >>
> >> > Don,
> >> >
> >> > That was probably a basic explanation, but still mostly over my head.
> >> >
> >> > It looks like voice coil actuators move linearly. If that's true,
won't
> >you need to convert that to rotary motion? If so, how?
> >> >
> >> > And if it's going to be driven by an audio amplifier, won't the
> >amplifier need to be pretty powerful if the voice coil actuator is going
to
> >be pushing a polishing tool around?
> >> >
> >> > What am I missing?
> >> >
> >> > Gary
> >> >
> >> >
> >> > >
> >> > >Gary,
> >> > >
> >> > >
> >> > >
> >> > >Voice coil actuators are neither complicated nor expensive. A good
> >> > >explanation can be found here:
> >> > >http://www.consult-g2.com/course/chapter11/chapter.html
> >> > >
> >> > >Voice coil actuators are commonly found in just about everywhere in
the
> >form
> >> > >of the loudspeaker. Voice coil actuators are simple enough to be
built
> >by
> >> > >the ATMer. I plan to use voice coil actuators because of the
simplicity
> >of
> >> > >driving them using off-the-self audio amplifier and off-the-self D/A
> >cards
> >> > >with a PC. The pseudo random driving signals are easily generated in
> >> > >software in the PC. I am using my favorite all-graphical software NI
> >LabView
> >> > >to do this.
> >> > >
> >> > >
> >> > >
> >> > >Don Clement
> >> > >
> >> > >Running Springs, California
> >> > >
> >> > >
> >> > >
> >> > >> Thanks Don,
> >> > >>
> >> > >> I looked up voice coil actuators - very interesting - though I
didn't
> >> > >understand much. The ones I saw looked like they weren't for
continuous
> >> > >motion. Is that true of all, or am I just not making sense of it? If
> >so, how
> >> > >would you use them for the machine?
> >> > >>
> >> > >> They also look expensive...
> >> > >>
> >> > >> With their rapid acceleration/braking/reversing and ability to
move
> >in
> >> > >very small increments would these be better than other motors for
scope
> >> > >drives?
> >> > >>
> >> > >> Thanks,
> >> > >>
> >> > >> Gary Fuchs
> >> > >>
> >> > >>
> >> > >>
> >> > >> >
> >> > >> >Gary,
> >> > >> >
> >> > >> >
> >> > >> >
> >> > >> >Periodic error by definition would produce a regular pattern.
> >Machines
> >> > >that
> >> > >> >use the same drive for spindle rotation and also drive the tool
will
> >have
> >> > >> >some synchronization and produce periodic component. That's why
my
> >> > >machine
> >> > >> >will use two independently driven voice coil actuators to drive
the
> >tool.
> >> > >We
> >> > >> >could test that theory by using the Lyot phase-contrast method
and
> >look
> >> > >for
> >> > >> >any effects of periodic error on the machine polished surface.
> >> > >> >
> >> > >> >
> >> > >> >
> >> > >> >Don Clement
> >> > >> >
> >> > >> >Running Springs, California
> >> > >> >
> >> > >> >
> >> > >> >
> >> > >> >> (First, thanks for the VFD info. That's on my Christmas list.)
> >> > >> >>
> >> > >> >> Don, Mike, et al?,
> >> > >> >>
> >> > >> >> I'm probably in over my head here, but why wouldn't the
periodic
> >error
> >> > >I
> >> > >> >think you're talking about actually be beneficial, making the
> >machine's
> >> > >> >action just slightly irregular and more human-like? Don't typical
> >> > >machines
> >> > >> >have at least two places where periodic error would occur, but
not
> >at the
> >> > >> >same time?
> >> > >> >>
> >> > >> >> Gary Fuchs
> >> > >> >>
> >> > >> >>
> >> > >> >> >
> >> > >> >> > Mike,
> >> > >> >> >
> >> > >> >> >
> >> > >> >> >
> >> > >> >> >We could test that theory.  Perhaps using technique mentioned
by
> >> > >Texereau
> >> > >> >in
> >> > >> >> >"How to make a Telescope", the Lyot phase-contrast method. One
> >could
> >> > >do a
> >> > >> >> >spatial spectrum analysis on the machine polished surface
using
> >the
> >> > >Lyot
> >> > >> >> >phase-contrast method to detect any periodic contribution due
to
> >the
> >> > >> >regular
> >> > >> >> >arraignment of balls in a ball bearing race. Since spindle rpm
is
> >> > >known
> >> > >> >and
> >> > >> >> >the ball bearing race configuration is known, one would know
what
> >> > >spatial
> >> > >> >> >frequencies to surface roughness to look for.
> >> > >> >> >
> >> > >> >> >
> >> > >> >> >
> >> > >> >> >
> >> > >> >> >
> >> > >> >> >Don Clement
> >> > >> >> >
> >> > >> >> >Running Springs, California
> >> > >> >> >
> >> > >> >> >
> >> > >> >> >> Don,
> >> > >> >> >>
> >> > >> >> >> Don Clement wrote:
> >> > >> >> >> > There is no contradiction.
> >> > >> >> >>
> >> > >> >> >> Yes, there was.  In one message you said there was no
effect,
> >then
> >> > >in
> >> > >> >> >> your next message you said there was.  Maybe it was a typo.
I
> >was
> >> > >> >> >> just trying to follow your reasoning.
> >> > >> >> >>
> >> > >> >> >> > Using a FFT Dynamic Signal Analyzer
> >> > >> >> >> > (such as the Agilent 35670A) and the proper sensors one
can
> >see
> >> > >the
> >> > >> >> >> > effects of rotating equipment using ball bearing races. In
> >fact,
> >> > >> >> >> > one can determine detailed information on the ball bearing
> >race
> >> > >> >> >> > parameters (such as number of balls, etc) by examining the
> >> > >spectrum
> >> > >> >> >> > of rotating machinery. There is no doubt that regular
spaced
> >balls
> >> > >> >> >> > in ball bearing races add some periodic component to a
> >rotating
> >> > >> >> >> > spindle of a polishing machine.
> >> > >> >> >>
> >> > >> >> >> I have no doubt you are correct in that statement - my day
job
> >is
> >> > >> >> >> signal processing and I play with FFTs all day.  I also have
no
> >> > >doubt
> >> > >> >> >> that the vibrations affect the quality of finish in metal
> >working,
> >> > >and
> >> > >> >> >> I found your post about 3-phase motors and speed controllers
> >very
> >> > >> >> >> interesting and useful.
> >> > >> >> >>
> >> > >> >> >> However, I debate your assertion that the miniscule
vibrations
> >will
> >> > >> >> >> cause measurable effects on the surface of a mirror being
> >polished
> >> > >on
> >> > >> >> >> a machine.  I certainly haven't detected any on my DC
> >motor/variac
> >> > >> >> >> setup, or on a machine that uses a PWM controller.
> >> > >> >> >>
> >> > >> >> >> I guess you'll end up with a grinding machine that can
double
> >as a
> >> > >> >> >> decent turntable for playing vinyl, should your Marantz
> >experience
> >> > >> >> >> problems.  :)
> >> > >> >> >>
> >> > >> >> >> (Yes, I know vinyl often sounds better.)
> >> > >> >> >>
> >> > >> >> >> Mike Lockwood
> >> > list http://www.atmlist.net/
> >> > _______________________________________________
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> >> >
> >>
> >>
> >
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