Flexible strip hot wire cutting guide

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MotoFairing

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I am looking for examples of the use of a flexible guide for hot wire cutting rather than trying to trace a sharpie line.

Something like using a couple rods of fiberglass that can produce a consistent bend and be pinned into place.

Once the guide is in place the hot wire can run along the guide producing an accurate cut with less mess, time or effort than a hand saw.

Does anyone know if this has been done before?
 

Tiger Tim

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^Yep, that.

Use your flexible fiberglass rod to mark a consistent curve onto some sort of stiff sheet that you’ll cut out and pin on as a pattern. This ought to help explain some:


The real meat and potatoes of what you want is at 16:20 but it’s all good stuff.
 

MotoFairing

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I would use a side and top template first but I would use the flexible guides to round the corners by repeatedly cutting off the corners.
 

wsimpso1

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I have NEVER heard of anyone free-hand hot Wire cutting.

Using a flexible spline as a guide seems to have two problems: securely anchoring a fiberglass rod seems problematic, and they are usually too flexible.

I use Masonite and 1/4” or thinner ply wood, have used aluminum. Using a spline to set smooth curves for the template is done.

Billski
 
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Bille Floyd

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...

I use Masonite and 1/4” or thinner ply wood, have used aluminum. Using a spline to set smooth curves for the template is done.

Billski
1/16" aluminum will yield the Smoothest ride for the hot-wire ; it
will not burn a divot and ruin the foam if ya go to slow. 1/16" alum
is also quite easy to cut into a pattern for your guide

Bille
 

TFF

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The only time I have seen freehand is someone cutting foam for shipping items to fit. Some for coring out with a soldering iron set up with a box shape to plunge cut. It should be pretty easy to Google templates to see best practices.
 

Norman

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I am looking for examples of the use of a flexible guide for hot wire cutting rather than trying to trace a sharpie line.

Something like using a couple rods of fiberglass that can produce a consistent bend and be pinned into place.

Once the guide is in place the hot wire can run along the guide producing an accurate cut with less mess, time or effort than a hand saw.

Does anyone know if this has been done before?
What you're describing is basically what we called a spline back in the days of hand drafting. It'll probably work but you'll need a lot of pins to hold it still while you cut and fastening the pins to the spline without altering the stiffness of the spline is important (a dab of hot glue may work for that). I use Formica, which is basically paper reinforced phenolic resin, for model airplane airfoil templates. It's smooth, heat resistant, and nonconducting so it doesn't cool the wire and make a little ridge like a metal template sometimes can. Fiberglass should last longer than Formica because the paper in Formica does eventually burn and get rough after a lot of cuts (Masonite has that problem too). You might need a separate template for the leading edge because fiberglass rods will probably be too stiff to go around that radius. Countertop shops usually have a dumpster full of Formica cutoffs large enough for that part. I've never paid for template material. Just ask nicely at the front office before diving in :)
 
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Pops

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I take a couple inches of larger wood dowel rod and drill a center hole a little larger than the dia of the wire on the cutting bow. I used one on each side of the bow for a handhold so I can hold my hand up close on the wire to the guide in cutting the foam. Gives more control. The heat of the wire will make the hole to get larger over time but you can always install new ones. Save your centers when using a hole saw in wood.
I make my guide patterns from scrap aluminum and polish the edges. I still have patterns that I used 55 years ago when making RC foam wings.
 

dwalker

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Late to the party as usual but I am working on a CNC hot wire cutter using 3D printer parts. These are already proven to work on RC wings, fuselages and other foam projects, but I am working (struggling really) with the existing programs being able to scale to the larger size of the cores the machine will need to work with.
 
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