IGCSE DT Booklet.pdf - design technology

With any process that involves heating plastics, it is difficult to judge thetime required. This is because darker coloured materials will absorb theheat more quickly than light coloured materials.For more complex forms, it may be necessary toheat the sheet all over using an oven. The oventemperature should be set to 170ºC. A curvedform can be achieved using a former madefrom PVC pipe. The softened acrylic is pulledover the former using a cloth stretcher. Thisprocess is called drape forming.More complex forms, such as trays and dishes, can be made form thinacrylic sheet using a plug and yoke press forming technique. For thisprocess a two-part former is needed. The male half, the plug, needs tohave tapered edges and rounded corners to assist the flow of material andremoval. The female part, the yoke, needs to be slightly larger to allow forthe material thickness.