shaping

Click a letter for the index

Or search the encyclopaedia:

 

 

Go

 

Method in which resistant materials can be fitted together to make structures that have shape. However, shapes can be made from single pieces of material. Irregular shapes can be made in sheet material by cutting with a fret saw or a coping saw. ‘Tin snips’ can be used to cut sheet metal into shapes. Chain drilling is a way of cutting shapes in the middle of sheet material. Shapes can be cut in resistant materials by using chisels, routers, lathes, and milling machines. Files and abrasives can be used to shape the edges of materials.

Materials can be shaped by forming or moulding. The material is placed around the former or in the mould and left to set until it takes the shape. To make a material ready for shaping, it may have to be heated until it softens. Forging, tempering, and annealing, when working with metals, uses this technique. Metals can also be hammered into shapes when cold.

Plastics can also be heated to make them into new shapes. Above a certain temperature range, plastics become elastic and then plastic. They can then be placed around formers or into moulds. Line bending, blow moulding, vacuum forming, and compression moulding all use plastics that have been heated in one of these ways. Plastics can also be heated until they melt. The molten plastics can then be placed in moulds and left to set. This is how extrusion moulding is carried out. Metals can also be shaped by extrusion, with aluminium alloys being a good example. Molten or liquid materials can also be shaped by placing them into moulds called casts. Once cool, the cast is opened, revealing the solid product. Many metal and plastic materials are made in this way.

The pan-African colours express African unity. Effective date: 1 August 1990. >>