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

To: atm@atmlist.net
Subject: Re: [ATM] Voice coil actuators was: DC Motor for grinding machine question
From: GARY FUCHS <gary@rcn.com>
Date: Tue, 21 Nov 2006 10:52:07 -0500 (EST)
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(To all) If I missed something crucial and am using up bandwidth unnecessarily I apologize.

Don, you said on Wed 15 Nov: "That's why my machine will use two independently driven voice coil actuators to drive the tool."

That's what I'm trying to understand. 

How will the - apparently - linear motion of these devices be turned into motion for a tool - especially motion that would be free of significant periodic error?

Beyond that I'm curious to know more about what you said on Sun 19 Nov: "Voice coil actuators are simple enough to be built by the ATMer." Do you mean voice coil actuators that could actually be incorporated in a mirror machine or something that would demonstrate the principles, like a science fair project?

Gary


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