Tools, equipment and processes

Most materials need specialist tools and equipment to shape and form them - polymers are no exception because of the unique properties they generally possess.

When marking out on the surface of a polymer, especially on a sheet of acrylic, a ‘chinagraph pencil’ is used as this will mark on the high-gloss surface. If no such pencil is available, an alcohol-based permanent marker would also work to mark a line to cut to.

Five different coloured chinagraph wax pencils laid out against a black background.
Chinagraph pencils

Polymers that are cut by hand are usually done by a coping saw, or sometimes a hacksaw - if it is a smaller piece of polymer then a junior hacksaw can be used. Once the polymer is cut close to a marked line, a file can be used to remove up to the desired line. Files can be bought in different shapes, sizes and cutting grades - a rough-cut file can remove polymers faster than a smooth file and should always be used first.

A blue, rectangular hacksaw with a black handle laid on a wooden background.
Junior hacksaw

It is very often the case that the polymer, for example acrylic, needs to be bent to a shape. Once the acrylic is cut, either by hand or using a laser cutter, it can be bent using a strip heat, often called a line bender.

The process of line bending, showing a thermoplastic heated again a heater bar and then bent into shape.

Acrylic needs to be heated to around 150 to 170 °C to bend without cracking, and jigs can be made in a variety of ways so that the bend produced remains the same as the acrylic cools.

Vacuum formers can be used for making moulds and housings for electronic products. High impact polystyrene (HIPS) is often the material used in a vacuum former, as it heats up quickly depending on thickness. The process is as follows:

  1. the HIPS is heated
  2. once hot, the solid former is pressed into the HIPS from a bed that can rise
  3. the vacuum is turned on, removing all the air from around the former
  4. the HIPS takes the form of the solid former
The vacuum forming process, showing heat being applied to a polymer within a vacuum former and the air being removed to shape the polymer around the former.
curriculum-key-fact
The solid shape that goes in the vacuum former is called a former; the hollow part that has been vacuum formed is called a mould.

Sometimes talc can be dusted on the former so that it drops out of the mould with ease. A good vacuum-formed mould will only be possible if a good former has first been made. The former must have a draft angle, so it doesn’t get stuck in the mould.

A mould with no draft angle, its walls straight and edges sharp at 90 degree angles, alongside a mould with draft angles, its walls turned inward and edges slightly curved.

Polymers can also be shaped, once hot, by press moulding and drape forming - methods often used to shape acrylic. Once the acrylic is hot and malleable, it can be pressed over a former to take a new shape.