Hot-wire foam cutter

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A hot-wire foam cutter is used to cut polystyrene foam and similar materials. The device consists of a 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.

1 Types of wire used
2 Foams suitable for hot-wire cutting
3 Types of cutters
- 3.1 Preformed Wire
- 3.2 Tensioned wire
4 Uses
5 External links

[edit] Types of wire used

Preformed manually or with pliers.
Rectilinear, tensioned 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.

[edit] Foams suitable for hot-wire cutting

All thermofusible expanded foams. This means those materials that melt to themselves 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®), very mechanically resisting 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.

[edit] Types of cutters

[edit] Preformed Wire

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

[edit] 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.