38 n SENSORS AND ENCODERS February 2024 www.drivesncontrols.com Lasers gauge strip metal thickness at Scottish plant Kilmarnock-based Mahle Engine Systems supplies aluminium tin bi-metal and sinter (copper/ bronze) bi-metal coils to the company’s plants worldwide. “The metal alloys that we produce are supplied in coils to other inter-group companies where they are used in the manufacture of automotive components such as engine bearings and thrust washers,” explains the company’s head of quality and process engineering, Charles McMillan. The Kilmarnock quality team decided that it needed some sort of thickness measurement system for the strip material that the plant produces. This material goes through various dierent manufacturing steps, including ovens and rolling operations to produce the desired strip thickness for customers. “We eventually reach a point in our production process where the alloy strip material is ready to be sent to our cold roll bonding mill, where it is bonded onto a steel backing,”says McMillan. “We already have a xed 100% inspection thickness measurement system and automatic gap control system on the cold roll bonding mill. However, this only gives us information on the bonded material output. We never really had any measurements of the incoming steel or of the alloy that we were producing in-house – just sample spot checks using a micrometer.” The team wanted a thickness measurement system that could provide them with process capability, but which would also be exible enough to be moved around dierent production lines and machines. It approached Micro-Epsilon to see whether it had a suitable thickness measurement technology. The sensor-maker suggested its thicknessGauge technology which uses laser triangulation sensors to measure thicknesses and perform quality control, either oine or inline. After an on-site demonstration of the technology, Mahle gave Micro-Epsilon sample strips from various steps in the production processes, allowing the sensor supplier to conduct some process/machine capability tests. The results of these tests gave Mahle the con dence that the technology would deliver the capabilities it needed. After a day of on-site training, the Mahle quality team applied the sensor at various stages of their production process “We now use the thicknessGauge to check the thickness of the incoming steel that we purchase, and to check the metal alloys that we produce inhouse before we send these for cold bonding,” McMillan reports. “Longer term, we’ll consider installing a permanent 100% thickness measurement system for incoming steel, for example, but at the moment we’re using the thicknessGauge to help us build up an overall picture of our process and machine capability at the plant.” Shapes As well as measuring thickness, Mahle also wanted to check the shapes of the strips as they move through its plant. Micro-Epsilon’s thicknessControl software has a function that allows the team to view the “warp”of the strip material. Essentially, this is plots the pro le of the top and bottom laser sensors, allowing the user to see if the material shape is bowed, curved or tilted. “If the strip is bowed, for example, it might mean that we end up with problems downstream when we have to match the alloy to the steel for bonding,” McMillan explains. “In this scenario, we would feed back to our steel supplier that they need to improve the shape of the steel, or we would have to focus on making our alloy atter.” The plant is already seeing bene ts from the new technology. McMillan says that in the nal process before the alloy strip goes to the cold bonding operation, the system has helped to identify potential issues. “On start-up,” he explains, “one particular batch of alloy strip was OK, but about 40m into the coil, the thickness of the strip became harder to control and was more than 100 microns outside the target thickness. This immediately warned us that there would be a problem in our downstream bonding process. The nished product would basically be out of speci cation.” Before adopting the new technology, the quality team took only sample measurements, so issues of this sort could be missed completely. “We wouldn’t know if the strip was the same thickness all the way through, or if it varied,”McMillan reports. “We can now check our various processes to see what we need to do to change the number of reduction passes on the alloy.” Although the plant is not using the thicknessGauge for xed, in-process control yet, the quality team believes that it will go down this route in the future. n A Scottish producer of bi-metal strip materials has adopted a laser-based technology to measure the thickness of the strip. The technology also measures cross-strip proles to check if it is warped, which would adversely aect the downstream cold-bonding process. Metal strip passes through the thickness measuring system at Mahle’s Kilmarnock plant. The laser sensors measure to an accuracy of ±2 µm. They have a 10mm measurement range and a 400mm traversing range.
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