Thermoplastics sheet materials soften when they are heated. When softened, thermoplastics can be bent, twisted and formed in a variety of ways such as by press forming, vacuum forming and by blow moulding.

Various types of heaters are used to heat thermoplastics so that they can be bent and formed, including: 

For line bending, a narrow strip of plastic is heated. Generally, the thicker the plastic, the wider the heated strip needs to be. 

Strip heater

Strip Heaters / Line Benders

Strip heaters, also known as line benders, consist of a resistance wire heating element (such as nickel-chrome resistance wire) that heats up when a controlled amount of current is passed through it.  

The heating element may be: 

These heaters radiate heat. Thermoplastic sheets are held close to the heating element but are not in contact with it. 

Line bending strip heater

Contact Heaters

Resistance wire heater elements may be encased in a metal or plastic sheath. These heaters are held in contact with thermoplastics. A metal casing with a hatchet profile is used to apply heat directly to a thermoplastic. Resistance wire encased in a metal band may be used to heat thermoplastic and metal rods, tubes and drums.

The diagram below illustrates a typical contact type strip heater consisting of resistance wire sandwiched between sheets of flexible silicone. Flexible silicone heaters may be used on curved as well as flat surfaces.

Silicon heaters for line bending

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