Numerical Control Systems for Machine Tools: A Survey of the Numerical Control Systems Currently Available in the United Kingdom and their Application to Machine Tools with Special Reference to the Aircraft Industry

Abstract

OF the 450 plus numerical control systems for machine tools currently being used in the United Kingdom, well over 100 systems are being operated by companies in or associated with the aircraft industry. In fact, the aircraft industry has probably done more than any other industry to pioneer, encourage and develop the use of numerically‐controlled machine tools. On the other hand, the application of numerical control within the aircraft industry itself is still in its infancy and it is therefore the purpose of this survey to outline the characteristics of the range of control systems now available. According to Report No. 119 entitled ‘Numerical Control: An Economic Survey’ by the Production Engineering Research Association of Great Britain, a survey revealed that many of the early applications of numerical control to machine tools were carried out without being economically justified. At that time, many of the advantages of numerical control were highlighted while some of the problems associated with their use were either not fully understood or ignored. However, the experience gained by a number of operators over a period of years has now put the use of this type of equipment into proper perspective. Since numerically‐controlled machine tools cost between li to 4 times as much as conventional machines it is necessary to justify this higher cost by direct or indirect savings. The direct savings, which can be measured and expressed in terms of time and money or both, may occur in (i) the pre‐production stage, by the simplification or elimination of jigs and tools, (ii) the production stage, by the elimination of marking‐out and reductions in setting, machining, handling and inspection times, and (iii) the assembly stage, by reductions in fitting or assembly times as a result of improved product quality. Indirect savings, which tend to be intangible, are: the reduction in lead times, the ease of design modification, the savings in scrap or rectification work, the reduction in jig and tool storage costs, and the reduction of operator fatigue. However, the picture has its greyer tones, and to brighten these a joint study convention was recently held by the British Electrical and Allied Manufacturers' Association and The Machine Tool Trades Association to foster such improvements as: the adoption of a common programming approach involving if possible a common numerical control language, the development of new machine tools specifically intended for use with numerical control systems and a greater degree of Government support for the introduction of numerically‐controlled machine tools used on Government production contracts. It is not the purpose of this article to describe the performance of machine tools equipped with numerical control systems but merely to present a survey of systems available. However, wherever possible examples have been quoted of the application of the numerical control system to particular machine tools—and a large number of these to machine tools being used in the aircraft industry. For a more detailed account of the application of numerically controlled machine tools, the reader is referred to the article beginning on p. 232, and to PERA Report No. 119. This PERA Report is a major contribution to literature on this subject and we are happy to acknowledge the use of a certain amount of the information contained in that Report in the following article.

Citation

(1964), "Numerical Control Systems for Machine Tools: A Survey of the Numerical Control Systems Currently Available in the United Kingdom and their Application to Machine Tools with Special Reference to the Aircraft Industry", Aircraft Engineering and Aerospace Technology, Vol. 36 No. 8, pp. 238-244. https://doi.org/10.1108/eb033912