Clamp down The X and Y axis.
I use strong spring to keep the cutting wire tight. The spring also keeps the wire tight when cutting a tapered wing.
You can get the spring in your local Home Depot. On some designs I have seen people using a bow instead of the spring design. I got better results with the spring, but feel free to experiment.
60V 3A variable voltage - will heat up to 60" of wire
The transformer is a power transformer from 40V to 60V at about 100W. You can find them on Ebay or at the link below
The router speed control can be purchased at www.harborfreight.com
The router speed controller connects to the mains voltage and its output goes to a transformer (should be isolated)
These transformers can be found in surplus stores like www.allelectronics.com or Ebay
Another way to go is to use an insolated variac - this is better since it provides isolation from the main power.
You can find variacs on ebay or search google for isolation variac.
Almost all variacs are NOT isolated, and by being not isolated, the user may get "zapped" if not careful.
Use caution when powering the hot wire, try to stay at low voltage (below 50V), in some cased you may need
to go beyond 50V - in case you have a long wire. make sure never to touch the wire or the springs.
A hot wire CNC foam cutters as its name - cuts the foam by melting it before having contact with the foam
EPS foam - expanded polystyrene at 1LB density can be cut at speeds from 10 to 20 inch per min
XPS foam - XPS foam has an innate combination of properties that make it one of the most efficient
insulating materials available. The closed-cell structure, responsible for the foam’s excellent moisture
resistance, also contributes to its high compressive strength and superior thermal performance extruded
polystyrene foams may need to cut at a slower speeds, from my experience, when cutting XPS foam,
I use a thinner wire - about 0.4mm.
XPS cut are generally smoother then EPS foams.
Another kind of foam is EPP foam (the kind they make the Zagi wing flyer) - EPP (Expanded Polypropylene)
EPP foam doesn't dent or break. It has a "spongy" quality to it, so on impact it compresses and pops back to shape
Hot wire:
We started out using stainless steel wire as our hot wire, this will work well, but the wire will not last long and can break
under to much tension. If cutting a 2LB foam for a large project, wire breaking during the cut can cause a lot of $$
At a later stage we moved to Nichrome wire. Nichrome wire will last longer and will not break even when red hot.
Keep in mind that the wire will tend to stretch when heated, so a spring is needed to keep it from sagging.
The software I use is foamworks (www.foamwork.net) This software is the most popular foam cutting controller software, and also not to expensive (about $50). It will control up to 4 motors and let you cut tapered wings and other shapes, take a close look at the site. There is a lot of useful information there, and even a link where people who built foam cutting CNCs post their pictures.
Some Sample Cuts:
EPS foam wings - tapered
EPS crown molding
EPS foam sign
