I was thinking to put power on the clips and use a heavy enough gauge copper
to make the resistance much less than the resistance wire.
The control circuit would pump current through the wire and monitor the
voltage drop. Divide to get the resistance, which tracks temperature. If the
temperature drops as you feed material, the controller would compensate with
more power.
Anyway, that's the idea. If you have a PIC controlling it, it would be
pretty easy. So if you're running narrow material, the PIC would measure the
length of the resistance wire while it was still cold by a resistance
measurement.
It would have the advantage of not burning your foam by ever getting too hot
and auto compensate for feed rate to an extent.
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On 9/5/06, turbulatordude <dave_mucha@...> wrote:
--- In CAD_CAM_EDM_DRO@..., "Dennis Schmitz"
<denschmitz@...> wrote:
The coefficient of resistance wire isn't as linear as platinum but it's
stable. You can design the current regulator to maintain a set
temperature
once you've calibrated it.
Come to think of it, this will be an average over the length of the
wire, so
if it's not all being used in cutting the foam, the temp wouldn't be
inaccurate. So if you string the wire on a tension mount with
insulators,
then bring the current in with copper wire and clips. Then you put the
length of the resistance wire doing the cut in the controller, or the
controller could measure it if it was cold. Should get an even
temperature
across the wire that way.
Just thinking out loud...
If I follow, one could put some sensing leads with alagator clips, and
'store' them on the ends of the wire. for many cuts, measuring that
would be good enough, then on the heavy cuts, one can move them to
the edges of the part....
or, would one put the power on the clips ?
or, does it really matter ?
