--- In CAD_CAM_EDM_DRO@..., "Phil Mattison"
<mattison20@...> wrote:
I use nichrome wire from the hobby store with spring tension, a 12v
transformer and a light dimmer. I've found that when cutting, the
foam draws
heat from the wire so the temperature (and therefore current) is highly
dependent on foam density, thickness and cutting speed. The wire expands
quite a bit when hot so the spring is needed to maintain tension. Unless
you're setting up a production system where repeatable conditions and
results are needed, it may make more sense just to play it by ear. I
just
turn up the power until the wire starts to glow, back it off a
little, and
start cutting. How much to back it off depends on the thickness and
density
of the foam.
--
Phil Mattison
I am starting to think that is how it is done. just heat the wire and
watch the cut.
I don't suppose it is anything difficult as I am trying to make it.
I was envisioning using a feedback so the cutting would slow when the
wire cooled, and/or adjust the current automatically.
Dave
----- Original Message -----
From: turbulatordude <dave_mucha@...>
To: <CAD_CAM_EDM_DRO@...>
Sent: Tuesday, September 05, 2006 7:36 AM
Subject: [CAD_CAM_EDM_DRO] Re: foam cutting current ?
--- 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 ?
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