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Re: [ATM] Voice coil actuators was: DC Motor for grinding machine question
Actually iron is more typically used.
Lawrence D. Lopez wrote:
> A solenoid is, I suppose, a voice coil actuator.
> All we are talking about is a coil and a magnet.
>
> This is absolutely nothing fancy about them.
>
> Without an iron core I don't think you will get
> enough force to do much of anything, though.
>
> If you want position to be related to voltage
> then you might need a spring, I think.
>
> Anecdotal:
> Old (circa 1960's) TV power transformers
> windings (without the core) could toss an axle of a baby
> carriage across a garage. It took a certain amount
> of, shall we say, talent to do this.
>
> Sadly the windings duty cycle was had to be limited to
> seconds. This was easy to regulate, you could see the
> wax melt.
>
> Larry
>
>
>
>
> Don Clement wrote:
>
>> 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
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> ATM mailing list http://www.atmlist.net/
>>>>>>>
>>>>>>>
>>>>>>>
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