Hot Wire Foam cutting CNC Machines

Home Built Hot Wire CNC Foam cutter
Day 1 - Vertical Y Axis
Day 2 - Horizontal X Axis
Day 3 - Lead Screw
Day 4 - Electronics
Day 5 - Finalizing the machine
Other CNC foam cutters
A New Design - Hot wire CNC Foam cutter
Foam Sample Cuts
Foam Cutting Videos
Links - RC stuff, Stepper Motors, Lead Screws
More information - about stepper motors

Links
FoamLinx Site - Foam Cutting CNC Machines
CNCLinx Site - CNC Router Tables
Foam Cutting Services - EPP, EPS, XPS
All About Foam Forum - Beta
Composites Prototyping and Design
Large and Configurable CNC Machines *
Online Store

Articles
How to coat EPS foam (Crown Moldings)
How to build an EPS Foam Recycler
How to build an EPS base and Cap cutter
How is EPS manufactured - molded
How to make RC foam planes
How to cut EPS, XPS, EPP foam
How to cut Polyurethane foam ( PU )
How to cut Acrylics - Laser cutting
DIY CNC Foam Cutter Blog - New

What is - more info about foam
What is EPS foam
What is XPS foam
What is EPP foam - Expanded Polypropylene
What is PE foam - Polyethylene foam
What is Polyurethane foam
What is Memory Foam

FoamLinx

Putting it all together

Clamp down both axis, one shown in the picture above.
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

Here is a setup which I also use on my foam cutting bow. The router speed control can handle up to 15A
And the power supply can supply up to 3.5A which is more then enough current for a 30" wire. (about 1.5A)
The low voltage power supply is used to isolate the main voltage (110V) from the cutting wire.

The router speed control can be purchased at www.harborfreight.com for about $20
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

Another way to go is to use an insolated variac - this is better since it provides isolation from the main power.
You can find this variac at http://www.action-electronics.com/variac.htm
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.
Here is a link to a large number of foils

Some Sample cuts

The white foam is EPS foam (Expanded polystyrene foam) the pink foam is XPS foam