DIY Induction heater for shrinker endmill holders?

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DIY Induction heater for shrinker endmill holders? rpseguin 04-24-2008
Posted by rpseguin on April 24, 2008, 3:41 am
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 I bought a number of BT40 Lyndex shrink fit endmill holders, but
cannot even come close to affording the shrink fit induction heating
system to operate them.
I'd like to use the holders, as they are really nice and well
balanced.

Soooo.... I was thinking of buying a $100 induction cooker and taking
it apart and reworking the coils to go around the endmill portion of
the holder.

It doesn't take a whole lot of heat to get the holder to open up
enough to take an endmill. I did an experiment where I used an
electric range cooktop and heated a 5/8" shrink fit endmill holder up
and then inserted a 5/8" carbide endmill. 30 seconds later, it had
really gripped it quite hard.
Opinions and ideas?

Anybody know if the coils in an induction cooker are flexible and can
be reshaped easily?


Posted by Winston on April 24, 2008, 4:00 am
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 rpseguin wrote:
> I bought a number of BT40 Lyndex shrink fit endmill holders, but
> cannot even come close to affording the shrink fit induction heating
> system to operate them.

Sayyy you may be on to something there.

http://en.wikipedia.org/wiki/Image:Induction_Cooker.jpg

The red dealie in the center of the (silicone?) pad is probably a
temperature sensor allowing closed-loop operation. So you would
want to incorporate it into whatever modification you plan.

Be careful to match the impedance of your inductor to that of the
spiral - wound unit shown.


--Winston

Posted by rpseguin on April 25, 2008, 5:17 pm
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Ok.
The coils look flexible enough to do it.
Can I cut out some of the coil to shorten it to suit this
application? Ie, will there be any problems with shortening the
coils?
I think it should be fine.
I figure I'll probably only turn the thing on for a few seconds to
heat up the holder and then change endmills/tools.

Thanks!


> rpseguin wrote:
> > I bought a number of BT40 Lyndex shrink fit endmill holders, but
> > cannot even come close to affording the shrink fitinductionheating
> > system to operate them.
>
> Sayyy you may be on to something there.
>
> http://en.wikipedia.org/wiki/Image:Induction_Cooker.jpg
>
> The red dealie in the center of the (silicone?) pad is probably a
> temperature sensor allowing closed-loop operation. So you would
> want to incorporate it into whatever modification you plan.
>
> Be careful to match the impedance of your inductor to that of the
> spiral - wound unit shown.
>
> --Winston


Posted by Doug White on April 25, 2008, 5:41 pm
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Keywords:
>Ok.
>The coils look flexible enough to do it.
>Can I cut out some of the coil to shorten it to suit this
>application? Ie, will there be any problems with shortening the
>coils?
>I think it should be fine.
>I figure I'll probably only turn the thing on for a few seconds to
>heat up the holder and then change endmills/tools.

I'm not certian, but if they build the circuit to resonate with the
inductance of the coil, changing the length will screw things up. Even
reshaping the coil so that the coupling between the windings is different
could be an issue, but that should be less of a concern than chopping it
up.

Doug White

Posted by Winston on April 25, 2008, 6:45 pm
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Provided I could locate the induction hob cheaply, I would try to design
a cylindrical inductor that would exhibit the same impedance as the spiral
inductor in the hob. Then I would cut up a silicone
hot pad to form a protective 'cup' for the endmill holder.

<http://cgi.ebay.com/BURTON-CERAMIC-INDUCTION-COOK-TOP_W0QQitemZ140226440993QQihZ004QQcategoryZ20685QQssPageNameZWDVWQQrdZ1QQcmdZViewItem>
Hmmmm.

Then I would devise a way so that the temperature sensor is in 'close
enough' contact with the endmill holder to allow closed loop operation.

Then I would replace the spiral inductor with my cylindrical part using
uninsulated crimp connectors. Then I would be very careful about not
shocking or baking myself!

Google 'spiral inductor calculator' like:
http://deepfriedneon.com/tesla_f_calcspiral.html

and again for a cylindrical inductor, to match the impedance of your
replacement to that of the original.

--Winston

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