Expansion compensated

r

Expansion compensated A new gauging system developed by Machsize is reported to compensate for thermal expansion when engineering components produced in quantity are being checked for size. The temperature of a component is measured by a solid-state optical pyrometer and displacement transducers check the size of the component. Signals from the pyrometer and transducers are processed by an electronic module, embodying advanced logic. Output of this analog processor is proportional to the size of the component at a specified reference temperature. It is directly applicable to an electronic column indicator, or similar display unit. When plenty of time is available, it is relatively simple to measure size with compensation for thermal expansion. The difficulty is in measuring temperature and in performing the necessary calculations at the speed of a modern production line. To solve the problem, Machsize utilized an optical pyrometer with a response time of 0.1 s and designed the electronics that process size signals to compensate for thermal expansion. The pyrometer is placed about 300 mm (12 in) away from the component, and its measuring beam is surrounded by an air curtain. Heat from metal surrounding the component would affect the reading. Owing to the large amount of metal present in a size gauging station, temperature is measured in another station where the component can be held in space. With the temperaturecompensated gauging system installed in a production flow line, the first station would contain the pyrometer. Temperature is memorized until size is gauged in the second station, when all signals are electronically processed to obtain the desired temperaturecompensated result. Piston m a n u f a c t u r e The first application of this temperatu re~ompensated gauging system is checking aluminium pistons by the Talbot Motor Co Ltd. Four parameters are gauged. One of these

PRECIS!ON ENGINEERING

is the diameter of the piston skirt, checked between two transducers. The others concern the gudgeon pin (wrist pin) bore which is checked by a Machsize electronic plug gauge equipped with four transducers. At opposite ends of the bore, the two diameters are gauged and the fourth parameter, taper, is checked by comparing the two bore diameters. A Machsize column indicator displays the reading for each of the four parameters. It contains the analog processor that accepts the memorized signal from the pyrometer, and supplies an output ;orrected to a reference of 20°C (68° F). As is normal practice in the motor industry, pistons are graded according to size. Signals generated by the column indicators are used to operate the automatic equipment that segregates rejected pistons and sorts the accepted pistons into twelve different grades. Machsize Ltd, York House, Clarendon Avenue, Leamington Spa, Warwickshire, UK, CV32 5PP

cnc wheel-forming Claimed to be the first form-grinding equipment which can be integrated in an automatic production cycle, the CNC Diaform aims to produce absolute consistency, without the problems of variations in accuracy which occur when form-grinding is done manually by people of varying skills. It is a departure from previous Diaform models which are based on the template/pantograph principle. The system consists of two elements: the CNC Control Cabinet, and the Dressing Unit which is mounted on the grinding machine. The Control Cabinet houses a "conversational programming" facility which guides the operator through precise steps via a vdu displaying short enquiries in the operator's language rather than machine codes. As each question is answered, the instruction given by the operator is stored in the unit's solid state memory and the next question is immediately displayed on the screen, until the program is complete. Part programs can be stored on the small magnetic tape cassettes supplied; each cassette can retain up to 32

different programs, each stored under its own part number. Before programming begins, the twin diamond tools on the Dressing Unit are set at the appropriate datum point, and this information is entered in a reference block called Data Block Zero. The program automatically takes account of the radii of the diamond tools. The CNC Diaform is available in two models: a three-axis model which will dress wheels automatically, and a four-axis model which can be interfaced with the grinding machine to provide a fully-automated production cycle. Either model can be fitted, in less than three hours, to most makes of conventional horizontal grinding machines, and to certain cylindrical machines depending on their geometry. Both models are available in two versions, one which will dress wheels up to 50 mm in width, the other for wheels up to 100 mm in width. Apart from the obvious benefits of time-saving, the CNC Diaform will enhance the technique of creepfeed grinding. In addition, its ability to re-dress grinding wheels automatically is of particular value when there are sharp corners on the form which tend to break down, and thus require frequent re-dressing. Diaform Ltd, Arundel Road Industrial Estate, Uxbridge, Middlesex, UK, UB8 2SB

Continuous path control The TNC 145 is a 3-axes continuous path control with linear and circular interpolation (2 ½ D) recently developed by Heidenhain and suitable for machine tools with backlash-free drives and simultaneous axes traverse. Position values (absolute or incremental mode) can be programmed in both cartesian and polar coordinates. Straight lines, arcs, the rounding of corners as well as tangential approach of a contour can be programmed with full tool compensation and up to a traversing speed of 10m/min. Spindle speeds can be coded or output as an analog signal. Dr Johannes Heidenhain GmbH, Postfach 1260, D-8225 Traunreut, FRG

49