Sensor system for inspecting the internal walls of bore holes
A development project for a bore hole sensor originally conceived by Micro-Epsilon in 2009 has now resulted in a commercially available sensor product. The miniature confocal sensor with a diameter of just 3.5mm can now be used for measuring bore holes with diameters of 4.0mm or higher. The sensor, which is rotated by an electric servomotor, can be used to measure a number of bore hole characteristics, for example, the diameter, roundness, concentricity, tapers and straightness. A sophisticated integrated precision ball bearing system provides the required rotation stability. The system comprises a stainless steel measuring head with integrated mechanics, a sensor probe with integrated confocal sensor, as well as two controllers. Similar to the linear standard systems, the confocal technology is suitable for numerous surface types. The system does not require any reference points during measurements, as it is able to recognise edges and steps. Measuring tapered bore holes is only possible at full power, otherwise the light spot is reflected past the optical system. However, in the case of a suitable target surface, a measurement of the diffuse reflection with reduced power is possible. Due to its compact installation length, the sensor can measure bore holes with depths of up to 90mm. In doing so, the sensor probe is guided into the bore hole using a linear unit provided by the customer. Depending on the application parameters, individual planes can be measured or a spiral profile of the bore hole can be produced. If different measuring ranges are required for a system, the sensor probe can be replaced easily and quickly. The system is used in industrial applications for quality inspection of bore holes in production lines or R&D test laboratories.