CAPSTANS TO COMPUTERS

By J. R. FAWCETT

Issued by British Information Services – The Certificated Engineer June 1965.

For most factories pneumatics offers the quickest and cheapest means of automation-for which the word pneumatation has been coined. Many firms are finding that it is the answer to rising costs and labour difficulties.

It is only within the last ten years or so that the full possibilities of pneumatics in the industry began to be realised. Previously it was confined to simple operator-controlled applications which entailed a single valve and cylinder. Modern developments are based on multi-cylinder applications, operating automatically in sequence, often with elaborate control circuits.

There are about fifty firms in this country today producing pneumatic components and unlike so many of our new industries, developments in pneumatics have relied almost entirely on British inventiveness and initiative. Most of the firms who were early in the field showed a marked individuality in their products which is still apparent, though tending to disappear. All makers take an active interest in the applications of their products and are prepared to co-operate fully with their customers from the conception of a machine until it is performing satisfactorily.

Compressed air is a very convenient form of power. It is clean, has no waste disposal problems, and is very easy to control. Most factories where it is used have compressed air mains which are tapped as required. This is by far the most economical way, as the diversity factor-the probability that only a proportion of the equipment will be working at once-means that a large potential demand can be met by a comparatively small compressor. Added to this is the power stored in the compressed air itself which can be drawn upon to meet peak demands.

Pneumatic components include the cylinders which apply power to the machine and the valves which control the supply of air to the cylinders. A cylinder is a barrel and piston with suitable seals and ports for the air to enter and leave. As very fast speeds can be obtained, stopping the piston without shock is essential and this is done by shock absorbers or 'cushions' incorporated in the cylinder itself.

Valves are obtainable in bewildering variety, the more common ones being made by mass production methods, with prices in shillings rather than pounds. The makers are some of the most enthusiastic users of their equipment in automating the processes involved.

Cylinders range in size from tin bore to 20in bore; size 4in bore and below are made in large quantities and are often held in stock by the makers. A 4in cylinder will give a thrust of about 1 000 lb. Larger sizes are usually made to order.

Cylinders can be mounted on a machine in any convenient place and are not hampered by having to provide mechanical linkages. They, therefore, give the designer a very free hand, and simple but efficient machines can often be made as veritable 'lash-ups' of standard components such as slotted angle, die-sets, and a few simple parts.

Machines can be fully automatic when the parts are placed in a hopper and fed by a cylinder into the tools, or semi-automatic when the parts are hand loaded and the machine stops at the end of each cycle. Awkwardly shaped parts, unfortunately, are still best handled by human fingers unless the quantities to be made warrant the development work often necessary if it is to be done mechanically.

Pneumatics blends in well with electrics and electric control and often they form ideal partners. For 1 s sophisticated purposes all-pneumatic control is usually preferred and push-button and switch-operated valves are almost identical in front-of-panel appearance with their electric counterparts.

One machine which has recently received attention is the traditional capstan lathe. of which there must be tens of thousands at work in this country. Each lathe requires an operator on whose conscientiousness the quantity and quality of the work depends.

These lathes are now being fitted with pneumatic cylinders to perform all the operations normally done by hand-chuck operation, stopping and starting, change speed, change feed, chip breaking, and tool feeding. The sequence of operations is planned and recorded by punching holes in a card which is then used as a template by the setter. Two operators can look after as many as eight of these machines and will obtain increased output and better quality. The forces exerted by the cylinders never vary and the only changes in size are due to tool wear. One unexpected result is that users prefer them to conventional automatic lathes. New machines can be bought ready equipped or existing machines can be converted into the owner's factory.

Where there are large numbers of one part to be made it is often economical to convert a standard tool of a suitable type into a special automatic machine by adding the appropriate pneumatic equipment. Such conversions can be made much more cheaply than when the machine must be freely versatile, as the control gear can be quite simple.

The first British air drills were developed soon after the First World War to speed up the manufacture of artificial limbs. There have, of course, been many developments since then, one of the latest being the self-feed drill which is very suitable for incorporating in automatically controlled schemes. These drills incorporate their feed mechanism which operates as soon as the supply valve is opened. They can be mounted at any angle and are often arranged in groups around the part to be drilled. One application is that of drilling simultaneously all the string holes in a tennis racquet frame. Multi-spindle nut and stud runners are widely used in the automobile industry for the assembly of cylinder studs, wheel-nuts, etc. Besides considerable time saving, there is the advantage of uniform tightening.

A considerable amount of research is being carried out on the more sophisticated applications of compressed air, chiefly as a competitor to electronics in computers and similar devices. It has many properties which make it ideal for this purpose and it is also one of the few media which can exert a force without consuming energy. Successful computer-like devices have been made but one of the principal problems is reducing the size of the components so that the large numbers required can be housed in a reasonable space. These are, necessarily slower than their electronic counterparts, but there are many potential applications where cheapness is more important than speed.