RELIABLE, REPEATABLE – WHAT CAN USERS EXPECT AS THEY MOVE FROM MANUAL MACHINES TO MODERN EARING MEASUREMENT

To answer this question, it is necessary to explain how Earing manifests in rolled aluminium. Can Body Stock typically produces a six-peak earing profile. This means that the edge of the cup exhibits 6 unique peaks of different heights, as well as 6 corresponding valleys. These peaks and valleys appear at defined angles relative to the metal grain – this occurs due to the superposition of metallurgical properties developed during both hot and cold rolling. For CBS, it is typical to see two particularly deep valleys perpendicular to the grain direction.

In contrast, hot rolled material typically exhibits a four peak earing profile. Peaks and valleys always appear in pairs, and again with each pair being directly opposite each other on the cup.

AMSLER manual testing devices are designed to measure four peak material. When taking a manual measurement, the operator rotates the cup on the contact height gauge and records the highest Earing reading displayed over one rotation. This highest reading occurs when the contact points align with the peaks and valleys and because there are four measurement contact points, and four pairs of peaks and valleys, good alignment is possible. In this case the Earing value given by the device will approximate the EN1669 calculation.

There are, as always, some caveats – real Earing cups often show slight angular offsets in the locations of peaks and valleys. The graph below demonstrates how a device with contact points at fixed 90 degree spacing will fail to find the true deepest point of a valley and therefore give an inaccurate Earing value.