NEW TEST RIG GUARANTEES REPAIRED SERVO MOTORS MATCH OEM PERFORMANCE STANDARDS
24 October 2005 - Wyko Industrial Services

The argument for conducting the routine maintenance and overhaul of servo systems can be clearly demonstrated by one of the UK's major car plants, where servo equipment on the production line is removed, checked, refurbished and returned to service by WYKO every five years, as a result, there have been zero failures to date. Companies such as this also require comprehensive documentation to support any work that is done on plant equipment, something the new rig is designed to provide.

The proven success of the service has led to increased demand and this is another of the main reasons why a replacement test rig was required; a higher capacity, improved reporting and greater accuracy were all necessities.

Typically routine servicing is based on four or five-year cycles and can be planned for, whereas a large amount of servo equipment installed during the nineties is starting to require attention. The increasing number of breakdown situations that WYKO are dealing with illustrates this. Breakdowns have to be acted upon immediately due to the obvious downtime implications, and put added pressure on both the repair team and the equipment. The test rig therefore has to be correspondingly robust.

'We knew the rig would be in virtually constant use, so wanted to design out breakdowns as far as possible,' said Vic Harris WYKO's Director for Electronic Developments. 'Unexpected stoppages would be disruptive to us, but potentially disastrous to our customers who often run 24 hours a day and therefore need to manage their spares and repairs with military precision.' WYKO's clients include BAE, transmission giants Ford Getrag and several of the food processing majors, alongside many smaller companies.

Basically the rig runs the test motors against a 22kW DC spindle motor controlled by a Sprint Electric four quadrant DC drive which is switchable between 'speed' and 'torque' modes to give both back driving and load testing capabilities. Back driving the servo motor is very important because it lets WYKO capture the set up data for each servomotor before it is dismantled, which in turn makes recalibration quick and simple.

Harris says he selected a Torqsense non-contact sensor, made by Sensor Technology, because it was the most advanced solution he could find and its non-contact characteristic isolates it from shock loads. 'The torque sensor is rated at 20Nm and can take 400 per cent overload, so it can cope with just about anything it is ever likely to experience on our rig. To be extra safe we have mounted it using Fenner Jaw coupling on both shafts, with the rubber inserts selected to take the sting out of any unforeseen shock loads.'

Torqsense monitors the shaft under test using a radio transmission head, which both supplies power to and picks up signals from two tiny piezo ceramic combs attached to the shaft. Rotational torque in the shaft contracts or stretches the combs, altering their radio emission signals in proportion to the torque experienced.

'Sensor Technology also supplied us with a software suite, Torqview II, which interprets the sensor's output signal in real time and presents it in ease-to-understand graphic form. It also logs and analyses the data, so we can print out a pass certificate for each tested motor.'

Thanks to the new test rig, WYKO's servo repair capacity has increased, and repaired servo motors now carry the same guarantee as the majority of new products (up to 12months). The rig also provides data on units as they arrive for service, allowing performance data to be compared and helping to identify potential problems before any work is carried out. WYKO also supply a full range of new automation equipment, ensuring a replacement is always at hand in the event that a motor should prove uneconomic to repair.

http://wyko.co.uk

More News:
  • For October 2005
  • From Wyko Industrial Services
  • For Motor Control