HOT-WIRE FOAM CUTTER

A 'hot-wire foam cutter' is used to cut polystyrene foam and similar materials. The device consists of a thin, taut metal wire, often made of nichrome or stainless steel, or a thicker wire preformed into a desired shape, which is heated via electrical resistance to approximately 200° C. As the wire is passed through the material to be cut, the heat from the wire vaporises the material just before it would have made contact with it, creating a smooth cut. The depth of the cut is limited only by the wire length. Width of cut is limited by throat, if any.

Contents

Types of wire used

Foams suitable for hot-wire cutting

Types of cutters

Preformed Wire

Tensioned wire

Uses

External links

Types of wire used

★ Preformed, manually or with pliers.

★ Tensioned, held tight by a frame with springs or (equivalently) by a bow. Many indicate a preference for single-strand stainless steel wire over nichrome wire, in diameters ranging from .008 inches to .020 inches for frame-tensioned cutters. Musical instrument strings and leader wire used for fishing lures are readily available and inexpensive. Commercial cutting equipment often uses the nickel-based alloy wire RENE 41®, a high-strength alloy resistant to breaking at high temperatures.

Foams suitable for hot-wire cutting

All thermofusible expanded foams. This means those materials that melt at a relatively low temperature:

★ Expanded polystyrene (blocks of expanded white balls).

★ Extruded polystyrene (in blue, green, gray, pink or purple smooth plates, depending on the manufacturer).

★ Plexiglas® (Rohacell®), excellent mechanical properties but very expensive.

★ Flexible expanded polypropylene foams, ideal for shock protecting.

★ Polyethylene foams, flexible and tear resistant.

★ Custom materials, such as the foams used in flexible fuel tanks to reduce explosion risks.

Types of cutters

Preformed Wire

A preformed wire is attached to a handle. The operator manually guides the wire through the foam to cut freeform shapes.

Tensioned wire

★ Handheld
A short tensioned wire is attached to a handle. The operator manually guides the wire through the foam to cut freeform shapes.

★ Template-guided
Templates placed on each side of a foam block are used to guide a taut hot wire to form a prismatic or tapered shape. The hot wire, tensioned with a bow or by springs attached to a rigid frame, can be propelled through the foam by hand or with a cord and pulley mechanism connecting each end of the hot wire to a weight.
Template-guided cutter accuracy is highly dependent on operator skill at fixturing the foam and guiding the hot wire along the templates. Accuracy is also affected by the precision to which the templates are formed and proper assessment and handling of kerf.

★ Computer Numerically Controlled (CNC)
Computer Numerically Controlled stages on each side of a block of foam guide a tensioned hot wire to form a prismatic or tapered shape. This is a four degree of freedom CNC system (one each X and Y on each side of the foam block).
Accuracy is affected by the precision of the stepper motors, backlash of drive systems, and stiffness of the races supporting the end effectors which hold the tensioned wire.

Uses

★ Signage

★ Architectural solid modeling

★ Props

★ Prototyping

★ Cement molds

★ Aircraft design

★ Model aircraft wing construction

★ Lost-foam casting

★ Surfboard construction

External links

★ Build Hot Wire CNC Foam Cutter from parts available at the local hardware stores

★ Digital hotwire foam cutter

★ Build your own hotwire foam cutter

★ Build your own hotwire foam cutter from Home Depot Parts

★ Large easy-to-build hotwire foam cutter

★ Build your own CNC hot-wire foam cutter

★ Build your own hot-wire foam cutter for $30

★ Discussion of merits of various tensioned wires