PRESS RELEASE
May 23, 1995
Automated magnetic-particle inspection improves quality and working environment

A new system for automatic magnetic-particle inspection of metallic components, known as AMPI, has been developed by Contest, a Swedish company which manufactures non-destructive testing (NDT) equipment. A system has recently been installed by Scania in a fully-automatic line for the production of steering knuckles.

The first station produced by Contest was supplied to Raufoss in Norway and was intended for testing shell casings. The Scania plant at Falun (Sweden) manufactures steering knuckles for trucks and buses, and inspection is carried out completely automatically. It is very important from a safety point of view that steering knuckles are crack-free, and high quality requirements therefore apply.
Test-pieces are collected by a robot and placed on a rotatable fixture. The steering knuckle is wetted, magnetised, and sprayed with powder from a specially-designed nozzle. After draining, a rotating ‘optical cylinder' directs UV-laser light onto the component, which is fixed while the optical cylinder rotates and scans the whole test surface with the laser beam. The optical signals are received and processed, and an alarm is activated, if a fault is detected. There is also a facility for manual post-checking.
Finally, the component is transferred to a robot which is supplied with information from the control system as to whether a fault has been detected, and accepts or rejects it accordingly.

Getting rid of a dark and boring job
Magnetic particle inspection is a widely tested NDT method. A metallic test component is exposed to an electromagnetic field and sprayed with water containing a fine suspension of ‘iron filings'. If there is a crack at or near the surface, the magnetic powder is attracted there by the field which ‘leaks' from the crack and holds the powder in place.
Up to now, inspection to detect these powder marks has been carried out manually. In order to make the powder more easily visible, it is treated chemically so that it fluoresces in UV light. The operator therefore usually sits in a darkened area shining a UV lamp on the test-pieces. The cracks are clearly visible, but they can still be missed, presumably because of the monotonous nature of the work in a darkened room.


Improved working environment and quality level
It is quite common to have frequent changes of operators because of the arduous and unpleasant nature of the work. With automatic inspection, these working conditions are avoided while component quality control can be improved.

The AMPI method
The component under test is illuminated with a UV-laser via several rotating mirrors, so that even geometrically complex parts can be tested. The mirrors are adjustable so that unimportant areas can be ignored. Light reemitted from the surface is detected and the detector signal transmitted to a computer programmed with acceptable deviation levels for comparison with a reference component. Tolerance levels can vary for different areas of the same test-piece: they may for example be higher on a ground section than on adjacent unmachined areas.
Contest AB manufactures and sells equipment for
NDT-based quality control. The systems are fully-automatic for crack-testing components in steel or other metals either in-line or off-line during production. The systems are based on electromagnetic testing, and consist principally of a sensor, electronic analysis circuit, and computer control, with an automatic handling and control system.
The company's sales are mainly within Europe, principally to the Scandinavian steel industry, but systems are also to be found in Asia and Africa. Contacts with partner companies in other European countries are actively sought.

Caption:
Automatic magnetic-particle test station at Scania's Falun plant. The picture shows the rotatable base, fixtures, and laser equipment, together with the wetting equipment and collector vessel.


For further information please contact:
Contest AB
Jonny Taflin or Karl Bergstrand
Box 6047
S-831 06 ÖSTERSUND
Sweden
Tel: +46 63 51 77 20
Fax: +46 63 13 30 22



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