In the field of polymer technology, injection moulding is the most important moulding process. Because of the size of that industry and the rate of development which it attracts, it is impossible to present, in a single reasonably sized volume, all of the developments that have taken place in recent years. The purpose of this book is therefore to present selected topics which contribute to, or exemplify, develop- ments in this important area. Each year considerable development takes place in the area of machine and process control and these developments receive con- siderable publicity in the trade press. Another area which advances at the same pace, but which seems to receive far less publicity, although it is equally important, is the area of mould design and manufacture. It is important because profitability is dependent upon the design, manufacture and operation of the mould. It is for this reason that several chapters relating to mould design have been included in this, the third volume in this series. The topics covered include advances in mould manufacture, the use of runnerless systems to aid productivity, and others showing how the applications of computers can greatly assist the moulder to obtain a more productive unit.