Home Built Hot
Wire CNC Foam cutter
Putting it all together - Updated June 2009
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
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)