Directly Deposited Thin-Film Strain Gauges for Force Measurement at Guide Carriages

Many industrial production processes use sensors to generate information about the manufacturing process. In this way, monitoring machine tools ensures the proper functionality of the system and detects unexpected behavior due to, for example, material inhomogeneity, incorrect data input, temperature influence, or tool wear. In large production machines, such as portal milling machines, the sensor equipment of guide carriages can be an important possibility since they are a standardized component and can be easily integrated into existing machines. Here, conventional polymer foil-based strain gauges show several disadvantages due to reproducibility and reliability of the sensor connection via adhesive. Thus, this article addresses the manufacturing of directly deposited chromium thin-film strain gauges on a guide carriage with integrated programmable data preamplification. Tests with different sensor materials on steel substrates showed that chromium was the most suitable sensor material with a high k-factor. Then, one end face of the carriage was polished before sputtering an Al2O3 insulation layer and a chromium sensor layer that was laser-structured afterward to produce two Wheatstone full bridges at previously simulated sensor positions. In a tensile test stand, the calibration of the sensors took place in the two spatial directions perpendicular to the guide rail direction. With an additional sensor data fusion for the final interpretation of measured forces, it is shown that this sensor technology is suitable for force measurement at guide carriages.