Cutting Styrofoam

If you do a lot of work with Styrofoam, a hot foam cutter will make the process easier and cleaner. Cutting Styrofoam with a knife does not always provide an even edge finish. You can end up with broken pieces and a large amount of dust accumulation. Hot wire cutters make hobby and production work faster and more accurate.

A hot wire cutter will slice through Styrofoam material leaving a clean finished edge. Crafters will find that they can easily create detailed patterns with the right equipment. A bow cutter or hand held device can be used for smaller cuts. Using a vertical cutter that is similar to a band saw in design will allow you to have both hands free for making intricate or larger cuts in the material.

Best Foams for Cutting

Rigid polystyrene, including expanded polystyrene (EPS) and extruded polystyrene (XPS)

Expanded polypropylene (EPP)

Flexible foam, polyethylene (PE)

Note: Do not use a hot wire cutter for polyurethane foam materials. Polyurethane can give off toxic gases when heated.

To cut patterns on a piece of Styrofoam board, draw the shape on the board with a fine marker or charcoal drawing tool. Move the foam along the hot wire with even pressure. Remove the largest sections of unwanted material first to allow more flexibility in your work. Fine details may need to be cut with a hot knife or other tools, save these for last. Curves can be created by slowly turning the foam board as you press against the hot wire.

Profile shapes can be cut by using a heavy gauge wire. The wire itself can be formed into curves or angles and then attached to the electrical connections on the cutter. Heavier gauges will work best for this; they will retain their shape with more accuracy. Once you get your techniques down you will find an incredible variety of patterns available for crafting projects.

Advanced designs can also be created on a specially made lathe. A foam block, with a hole in the center, is placed on a rotating rod. The foam is then turned against the hot wire at the depth desired for dimensional work.

Hot Wire Sizing and Cutters

Hot wire cutters can be used for crafting and commercial or industrial Styrofoam work. You will find many choices in sizes and styles of cutters available. You can even make your own equipment for cutting Styrofoam using electrical resistance wire. When you build your own cutting device, you can add features like temperature controls and dual wires for cutting. Adding a potentiometer is one way to control the amount of heat.

Choosing the correct wire to use is critical if you are making a hot foam cutter. The wire must be able to withstand the temperature needed for cutting Styrofoam cleanly. You want the wire to retain its shape without distorting or breaking. Tension must be applied to the wire without causing it to snap. Nichrome wire is one of the best choices for use in a hot wire cutter. Galvanized metals are strong but they can release fumes when they are heated.

The diameter, or AWG size, is a factor in how much resistance the wire will provide for heating. It can also be a factor in the type of cuts you are making. Fine or small cuts call for a thin wire. Large cuts will be faster with a heavier wire.

Nichrome provides a high tensile strength and high melting point. It offers durability for continuous use. Most foam products will require a wire capable of reaching 600°F (315°C) or higher. To heat 18 AWG Nichrome to this temperature range will require 6.5 amps. At 20 AWG, you need just over five amps. With a 26 AWG Nichrome wire, only 2.1 amps are required. A 26-gauge wire is a good choice for a lower power requirement and appropriate cutting size.

TEMCo carries a range of gauge sizes in Nichrome 60, Kanthal A-1 and Kanthal D wires. The professionals at TEMCo are ready to assist you in selecting the best type and size of wire for your hot wire cutting needs.

Safety Considerations

Before you begin using hot wire for cutting Styrofoam, check with the foam manufacturer, or Material Safety Data Sheet (MSDS) for any safety or health hazards in heating the foam. Always work in an adequately ventilated area to prevent inhaling fumes. Use a dust mask, the mask will also protect against airborne dust particles.

Most foams materials do not present a fire hazard. Smoke that rises while cutting Styrofoam is mostly made up of water and hydrocarbons. Once the heat is removed from the foam, it will stop burning or melting.