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

[GARY FUCHS <gary@rcn.com>]

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/
>> > _______________________________________________
>> > ATM mailing list http://www.atmlist.net/
>> >
>>
>>
>
>_______________________________________________
>ATM mailing list http://www.atmlist.net/
_______________________________________________
ATM mailing list http://www.atmlist.net/