PART TWO: POWER AND ENGINEERING 422 CONTROL REVOLUTION AND ELECTRONIC METROLOGY Alan Turing’s work on calculating machines enabled him to design the machine to decipher the German ‘Enigma’ machine codes and he built an electric computer with memory in 1944. In 1948, John Parsons in the USA was transferring the ideas of punched-card control of accounting into the control of machine tools by demonstrating with a universal precision milling machine that all its movements and speed changes could be controlled by mathematical computation. A government contract for more development was given in 1949 to MIT Servo-Mechanisms Laboratory, which produced the first numerically controlled (NC) machine tool in 1954. The system was based on a Cincinnati vertical spindle contour milling machine modified to servo control of table, cross slide and spindle through hydraulic units, gears and leadscrews giving a motion of 0.0005in (0.0127mm) for each electrical pulse received from the control unit. This was provided by a valve electronic unit and Flexowriter using eight-column paper tape to represent an eight-digit number on each line, with holes as units and unpunched positions as zeros. Feedback, the basis of automation, was provided by synchronous motors geared to the slide motions which provided electrical signals to the control for comparison with the input signal to verify the slide position. This machine, and the report on its practical possibilities, was the beginning of NC machine development taken up by many companies. Giddings & Lewis produced Numericord, a contouring machine for aircraft frames which employed magnetic tape to control five axes of motion simultaneously. This system required a computer to interpolate the decimal calculations of points on the profile entered from paper tape, which was then time co-ordinated and recorded on the magnetic tape to give contour control. Other systems were limited to ‘point to point’ control of the tool position and employed simple electrical relays and limit switches. The next step in development came with automatic tool change to increase the range of operations performed, the first example being the Barnes drilling machine in 1957 which employed four spindles that could be used in turn. The full concept of a single spindle which could take a number of tools was that of Wallace E.Brainard, who in 1958 designed the automatic tool changer for the Kearney & Trecker Milwaukee Matic machining centre, the first numerically controlled multi- function machine capable of automatic tool changing. It was a horizontal spindle machine with work mounted on an indexing table so that four sides could be machined. A rotary drum on the side of the machine held 30 tools coded on the shank so that they could be selected at random. Tools were collected by a double- ended arm which gripped the tool to be changed, indexed 180° and inserted a new tool in 8.5 seconds. This was the first NC machine imported to Britain, where similar efforts were being made to establish numerical methods of control. Ferranti, in conjunction with Serck, produced a control system to drive a ENGINEERING AND PRODUCTION 423 numerically controlled drilling machine to produce the large number of accurately positioned holes required in the end plates of heat exchangers in 1956. Ferranti also produced in 1959 the first co-ordinate measuring machine, which employed linear diffraction gratings to measure distances on two planes by electronic counting of fringe movement. Many similar optical grating systems have been developed and fitted to machine slides and spindles using photo cells and electronic counters to give accurate positional readings. Electrical gratings such as the EMI Inductosyn use a similar principle, alternating currents in the fixed grating inducing currents in the slider which can be used to indicate position. The latest use of the diffraction grating is in the hand-held electronic micrometer developed by Moore & Wright in 1973 from designs made by Patscentre International. It employs fine pitch gratings of 0.004mm, produced photographically, and a special micro circuit to count the optical fringe movements registered by the photo cell to allow the micrometer to read to 0.001mm or 0.0001in for the inch version. Post-war research and development in all areas of manufacturing has become more and more costly as the equipment required to make advances has become increasingly complex, and in consequence this has become a company-based operation with large R & D departments continuously making improvements in products which are progressively more anonymous and difficult to assign to individuals. In metrology it was still possible to identify the work of Reason at Taylor-Hobson on the measurement of spherical and cylindrical parts and the problem of ‘lobing’, whereby a dimension may be judged true by diametrical testing but is ‘out of round’. A machine was produced to his design to cope with the measurement of ‘roundness’ in 1949, the Talyrond, although it was six years before similar machines were made for sale. The machine employed a large vertical column carrying a stylus and electrical transducer which could rotate about the table holding the piece being tested and a circular graph rotating in phase with the spindle to show the variations in the surface of the specimen. Modern developments have enabled the original valve amplification to be up-dated on both Talysurf (see p. 415) and Talyrond, and computers are now used to provide digital sampling and give arithmetical results of surface texture and roundness. The development of electronics in the Talysurf and Talyrond influenced the company to produce an electronic level to complement their optical alignment telelescope and autocollimator in checking the straightness of surfaces. A pendulum design was finally produced whereby a weight suspended on thin wires would act as an armature for an electro-magnetic transducer. The Talyvel, as it is called, competes with the photoelectric collimator as the most accurate instrument available today for surface contour measurement. The general machine tools also underwent the control revolution in arrangements for programming slide operations, tool indexing and speed changes by the use of electrical relays, limit switches and hydraulic servo- PART TWO: POWER AND ENGINEERING 424 mechanisms. Many manufacturers produced ‘add on’ devices for standard lathes, and by the mid-sixties most lathe manufacturers had modified their main lines to provide plug board control of spindle speed and feed rates to cross slide and capstan slide. The ‘plug board’ consists of a grid of holes, each vertical line corresponding to a step in the sequence of operations, and each horizontal line to a command signal input. When each vertical line is energized all ‘plugged’ functions will operate simultaneously, and when a timed or external signal, such as that from a limit switch, has indicated completion of these functions the next column is energized. The controller continues stepping line by line until the full cycle is completed. The ultimate development of this type of control appears in the purpose-built lathe by Alfred Herbert named the 3M Robot in 1977. This provided spindle speed control by pneumatic valves and hydraulic feed to front, back, profile and turret slides. Similar ‘plug board’ controls were introduced on milling machines such as the Parkson Miller-matic of 1964, which had a separate free-standing console containing the electrical circuitry. At the same time some manufacturers were adopting more sophisticated and expensive numerical control methods such as that for the Société Genevoise Hydroptic 6A first made in 1958, which also incorporated design features of production machines added to their jig borer accuracy. One-inch eight-column paper tape is used to control all the functions of the machine, and accurate table settings are achieved by synchronous motors and photoelectric microscopes. The Dowding ‘Atlantic’ two-axis co-ordinate drilling machine of 1964 used the Ferranti control system with eight-hole paper tape input, transistorized circuitry and feedback of positional information by the use of diffraction gratings, ruled to 1000 lines per inch, and optical block scanners on the co-ordinate positioning table. In the 1970s even standard machine tools with the usual hand controls were being fitted with linear and radial gratings to slides and leadscrews to be read by photo cells and translated by electronic processors to provide amplified digital read-outs for simplified control. FLEXIBLE MANUFACTURING SYSTEMS In large production factories Britain long persisted in a 1950s design of manufacturing systems, organization and job structure originally arranged to suit high-volume, low variety markets in Henry Ford style, but technological change had entered an accelerating spiral and market demands required greater flexibility. The dedicated transfer machine, with its high cost and rigidity of operation, could only be justified commercially by large-scale production of a constant product design, and this type of machine has been replaced by conveyor linked systems of standard machine tools and machining heads which can be easily dismantled and rearranged to accommodate design ENGINEERING AND PRODUCTION 425 changes. Increasing use of bowl feeders and parts dispensers with devices to manipulate workholding jigs between machining sections established automation at the stage when overall control by computer, integrating all the individual machine programme sequence control, became a possibility. By 1969, D.T.N.Williamson had completed the first flexible manufacturing system (FMS) in the Molins System 24, which provided a range of machines capable of performing multiple operations on parts with different configurations. Each machine in the process had a single horizontal spindle and a tool changing system controlled by a computer program which also controlled depth of cut, feed rate, cutting speed on each cycle and the transference of workpieces between stations. Virtually any part within the physical capacity of the machines could be completely machined by this system, which also featured swarf collection by conveyor and sophisticated oil cleaning and pumping for the hydraulic servo mechanisms. The system, patented in 1970, is a notable British ‘first’ in manufacturing organization. The extension of the range of control became possible with the introduction of the concept of computer aided design (CAD) in the USA. This is a method of drawing ideas of shape on a video display and recording them. In the 1960s experiments were made in Britain on interactive graphics using mainframe computers, and since the appearance of microcomputers in the early seventies the techniques have grown rapidly. Pictures are changed by electronic pen, keyboard or digitizers which convert analogue information to digital to allow its manipulation and presentation in the computer. A database of design principles, information on materials and so on is required and is time consuming to prepare. The software for the Clarks Ltd shoemaking CAD took four years to design, but allows presentation and modification of shoe style, colouring and flattening to provide the patterns for leather cutting. CAD can make tapes for numerically controlled machine tools by drawing cutting paths around a two-dimensional drawing which is the basis of computer aided manufacture (CAM). With the control tapes for CAM to provide the instructions for component machining by the numerically controlled machine tool, and the development of mechanical handling and inspection machinery which is also controlled numerically, the target of completely automatic manufacture is achievable. The mechanical handling devices required are the flexible manipulator, the robot and transporters, automatic guided vehicles (AGV). The name ‘robot’ first appeared in the play R.U.R. by Karel Capek, performed in London in 1923, for human-like machines created by Dr Rossum to perform tasks. The modern industrial robot is not humanoid in form, but some of the threatening myths attached to fictional monsters, and the Luddite fear of machines which destroy jobs, have had an effect on their acceptance. The simple robot in industry consists of an arm and gripper which operates in only three axes, as the simple ‘pick and place’ device used to transfer parts between work stations. To this may be added a rotational movement to give PART TWO: POWER AND ENGINEERING 426 increased scope. The articulated arm with dual jointed wrist and elbow movement to give six axes of freedom is the most generally accepted ‘robot’ with central control by computer, a manipulator at the end of its arm and a sensing device. The most usual sensors are touch, pressure, heat, and vision through photo cells or TV camera. George Devol in the USA invented a programmable robot and made a patent application in 1954. Joseph Engelberger, the founder of Unimation, the biggest manufacturer of robots, met Devol in 1956 and began manufacturing his ‘Unimate’; although it was found to infringe a British patent for an industrial robot filed in 1957 by Cyril Walter Kenward, a cash settlement cleared the way for further development in the USA. The first British robot was designed and produced by Douglas Hall, and Hall Automation began in 1974 with a paintspraying robot called RAMP (random access multi programme). Most of the early applications of robots were in paint spraying, welding and other operations with hazardous environmental conditions, and automobile manufacturers became the largest users. Further improvement in hydraulic drives and the alternative stepping motor, as used in the Swedish ASEA robot, combined with precise feedback control made possible by the incorporation of micro-processor systems, created the accuracy and consistency of placement required for the use of robots in precise assembly work. Modern robots are now capable of returning to the same spot repeatedly within 0.005cm (0.002in) at a speed of 5m (200in) per second and will work continuously for long periods. Visual sensing, first introduced by Hegginbotham and Pugh in laboratory conditions early in 1970, has become the immediate goal of development for applications in assembly work from conveyor supplied parts and in inspection between stages in ‘cell’ manufacture. A visual sensor was produced at Oxford University in 1984 incorporating a solid state camera to operate while the robot is welding seams using a laser. General vision systems using multiple microprocessors to interpret video picture elements to allow recognition by robots are becoming available to industry and have already been used in medical research. Increased flexibility in use is demonstrated by the Cobra system produced by Flexible Laser System of Scunthorpe in 1983 which uses a 400W CO 2 laser made by Ferranti Incorporated in an ASEA robot which can cut, trim, weld and drill holes in a variety of materials. The value of the AGV was first demonstrated in the FIAT body shell production layout in 1979 through their need to achieve flexibility in meeting market fluctuations economically. Assembly and welding is fully automated and can produce different models in any sequence. Robot welders operate within each gate and the AGVs, electrically powered and under the guidance of the central computer, carry body shells on coded pallets to them. The use of AGVs to achieve out-of-sequence operations helps to make more economic use of workshop floor space and get away from the operational sequence organization of flow production (first seen by Pero Tafur, c. 1439, in the ENGINEERING AND PRODUCTION 427 equipping and victualling of ships in Venice) by achieving the flexibility of batch production through the use of manufacturing cells for similar products using group technology and FMS principles. The AGV is also a key factor in the creation of computerized warehousing for stock material, finished products, packing and dispatch using underfloor cables carrying instructions. Three-dimensional co-ordinate measuring machines with computer control of the sensing probe are now in use, with the necessary feedback system to provide information to the main control computer on faulty operations and they could be incorporated in overall manufacturing systems with robot interface between the machining centre and measuring machine. One of these measuring machines, built by the Mitutoyo Company of Japan, can be seen in operation at the Science Museum, London. THE AUTOMATIC FACTORY With the addition of the business systems, computer control of the whole process of manufacturing from market forecast to dispatch could be achieved. Computer integrated manufacturing (CIM) would incorporate: forecasting of finished product demand; customer order servicing; engineering and production data source; master production schedule—planning with alternative strategies; purchasing and receiving—quotations, orders, quality and storage; inventory management—quantities and timing to meet plan; order release — authorize production; manufacturing activity—use of capacity at start, minimize ‘work in progress’ and manufacturing lead time; plant monitoring—control of order through shop, co-ordination of inspection; materials handling; plant maintenance—labour utilization, preventive maintenance; stores control-— materials location; cost control—production information for accounting. One of the most advanced examples of total automation in the UK, and an operating CIM, is the JCB Transmissions factory in Wrexham producing gearboxes for earth movers. Computers control routine operations and machines, while the master control computer, programmed daily, is in charge of the overall management of the factory. There is manual overview and manual intervention if necessary. The basis is the high-value low-volume FMS for the gearbox cases, the assembly and inspection system, and the automated warehouse, all linked by AGVs. The FMS consists of seven machining centres with large tool magazines containing 80 different tools and capable of machining thirty-two variations of components. Measuring and washing machines are also controlled by the computer which is programmed weekly. Six AGVs are used to carry work between these stations and general distribution work. The AGVs are programmed to follow induction loops in the factory floor with an on-board microprocessor for driving to the loops. Two PART TWO: POWER AND ENGINEERING 428 assembly lines using five manned stations have additional small AGVs to carry parts between them. The plant became operational in 1986. In the same year, Yamazaki Machinery UK built a new machine tool factory in Worcester at a cost of £35 million to produce machining centres, which are the building bricks of FMS. The factory is temperature controlled and all machining, storage, fabrication and assembly is under CNC. Precision grinding and jig boring is accurate to less than 5µm, parts are fixtured and palletized by robots and transferred by automatic stacker cranes, prismatic machining is carried out by machining centres and lathes allowing multiple operations in one fixture. Sheet metal work is similarly controlled using laser cutting and automatic folding, bending and welding machines. The software control system for the CIM, which took 40 man-years to develop, runs on an IBM 8/38 computer for central control of production and scheduling and three DEC Micro Vax FMS-CPU operating the on-line system. Many assembly operations, such as those in the electronics industry, are highly organized. With controlled positioning of the chassis or board for fitting, the required component is presented in a dispenser, the location for the component indicated by a light beam, and a picture of the component presented to the operator, all under computer control, so that all the operator has to do is grip the component, place it in position and operate some fixing device. This seems only a small step for a robot to take—perhaps it represents a giant step out of the factory for man. PART TH RE E TRANSPORT 431 8 ROADS, BRIDGES AND VEHICLES IAN MCNEIL ROAD CONSTRUCTION Before men began building roads, there were merely tracks, sometimes deliberately cleared but more often worn by repeated passage of man and his domesticated animals from one place to another. In sandy country tracks started by such traffic tended to be enhanced by the subsequent rush of rainwater so that hollow ways were created as much as twenty feet deep, as in parts of Surrey. In marshy lands, like the Fens of eastern England or the Somerset Levels, timber trackways were laid down showing concentrated labour by the relatively small populations of the time and concerted action. Carbon-14 dating has established that these originated as early as the years around 600 BC. The making and use of such trackways presupposes the establishment of permanent settlements —encampments, and later villages and towns. (The walled city of Jericho, built around 8000 BC, is generally accepted as being the first major urban centre.) The routes taken by these early tracks generally followed the easiest possible path, avoiding excessive gradients, dense woodlands, soft marshland and crops, where these had been sown. They also tended to follow the higher slopes of the hillsides where possible, so as to avoid the possibility of attack by an enemy from above. Many of Britain’s roads today follow the routes of the trackways of primitive man, which accounts for the somewhat erratic courses that they pursue. The application of the wheel to transport, said to have originated at Erech in Sumeria about 3500 BC when tripartite or board wheels were first added to a sledge, allowed much greater loads than could be carried either by men or on the backs of pack animals, and this called for more substantial tracks to . operations and machines, while the master control computer, programmed daily, is in charge of the overall management of the factory. There is manual overview and manual intervention if necessary. The. avoid the possibility of attack by an enemy from above. Many of Britain’s roads today follow the routes of the trackways of primitive man, which accounts for the somewhat erratic courses that they. large-scale production of a constant product design, and this type of machine has been replaced by conveyor linked systems of standard machine tools and machining heads which can be easily dismantled and rearranged