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

[GARY FUCHS <gary@rcn.com>]

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
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