Switch to zero defect production

Citation

(2000), "Switch to zero defect production", Assembly Automation, Vol. 20 No. 3. https://doi.org/10.1108/aa.2000.03320caf.001

Switch to zero defect production

Switch to zero defect production

Keywords: Automated test equipment, Production

A recent series of assembly and test machines that has been designed and constructed by Tamworth-based CPR Automation Ltd are centred on standard Yamaha 3-axis robot arms (see Plate 1). The machines were commissioned by a major manufacturer of automotive switches and the introduction of them into the production facility has made it possible for the company to market its new generation of products on a zero defect basis.

As cars and trucks become more complex, so there is a tendency to replace the conventional electromechanical switches that are normally used for windscreen wash-and-wipe functions, electric windows, direction indicators, and so on, with low current devices which are capable of being incorporated into network-type wiring looms.

Plate 1The recent series of assembly and test machines are centred on standard Yamaha 3-axis robot arms

Two different categories of switch are manufactured on the CPR machines: those designed to control electrically-operated windows, mirrors and seat functions; and those for direction indicators, headlamp and windscreen wash-and-wipe control functions.

As the production of these latest types of switch takes over from earlier generations, so there are greater demands for new and more stringent testing methods, but of a simplified nature. In line with these demands for volume production, CPR's test equipment has been designed for use by a single operator who controls and monitors every stage of the process as the switch is sent through the assembly, test and packing stations.

In a typical test machine, the operator initiates the automatic cycle by the action of pushing a fixture of switches into the machine. At this point, a Yamaha 3-axis robot arm, which has been mounted above the fixture area, takes over the functional testing of the switch. The robot carries a single contact probe and has been fully programmed in the X, Y and Z axes. It is sent to the switch fixture where it identifies the type of switch that is being tested, selects the program and commences the test procedure by depressing the first button on the switch pack.

The test operations performed on the switches involve the measurement of the operating force, contact bounce time, contact continuity and a check for mismatched or badly-connected contacts. The robot carries out this cycle of tests by moving the probe to each switch in the pack, in turn. Each button is depressed to a set position, at which point the force exerted is measured and checked to see that it is within the specified magnitude of 2-5 newtons.

When the force test has been completed, the electrical resistance of the contacts is measured to ensure that it is the required 100'ohms. A further check is made to ensure that there is no cross-tracking between the switch contacts. The test routine, which takes approximately 4.5 seconds for each button actuation, is then repeated for every button on the switch pack.

Switches that pass the test are marked in yellow by means of an inkjet printer and are manually released from the fixture when the operator is unloading. Failures are trapped in the fixture and can only be released by a nominated operator or supervisor. On completion of a successful test, the machine automatically prints out a shipping label for attachment to the switch prior to despatch.

A rack-mounted PC, complete with a set of data capture cards to measure the switch resistance value recorded for each button contact resistance, is supplied with every machine as a control and monitoring system. The test results are displayed to the operator on a mimic panel while the electrical characteristics of every switch placed on test is recorded and analysed by the PC. This enables full product traceability for every switch tested by the system to be provided.

For further information, please contact: David Riley, CPR Automation Ltd, 7 Apollo, Lichfield Road Industrial Estate, Tamworth, Staffordshire B79 7XH. Tel: +44 (0)1827 57475; Fax: +44 (0)1827 62354; E-mail: CPRAutomation@dial.pipex.com