Image profiler

US researchers have developed a technique for measuring the surface roughness of metal used to shape car bumpers and other body parts that they claim is more accurate than current procedures.

Instead of the traditional method of measuring with a linear profilometer — which can only view sections of an image — the team, from the

(NIST) uses data from a scanning laser confocal microscope (SLCM). This has the advantage of being able to look at an entire image.

Surface roughness is a key issue that goes beyond cosmetics. Faint striations and other marks that appear when metal is shaped can indicate residual stresses that could cause the part to fail. They also lead to extra wear and early retirement for expensive stamping dies used to form sheet metal into body parts.

Measuring this roughness can help predict friction and the metal's 'springback' — the amount it will unbend after being stamped. Springback has to be known and controlled to build accurate dies for complex metal shapes.