On-machine tool wear estimation using a portable digital holographic camera

Machine tools are integral part of the machining process and they require regular monitoring for detection of wear of the tool to control the surface finish of the machined products, e.g., mechanical and optical components and assemblies. In this work, we report application of an indigenously developed compact and portable digital holographic camera for wear inspection and metrology of cylindrical end mill and square shoulder face mill machine tools. The camera utilises principles of digital holographic interferometry for wear inspection. It provides direct access to the complex amplitude of light scattered from the test object, which makes the camera suitable for quantitative analysis of irregularities present on the test surface. Wear as well as cracks in the tools incurred during machining process are analysed qualitatively as well as quantitatively by applying the digital holographic interferometry technique. The developed digital holographic camera is also suitable for in-situ inspection of machine tools. The experimental results are validated by a standard mechanical profiler and a measurement error of around 9% is reported. The results presented in this manuscript can be of significant importance in deciding the tool replacement time in the machining process based on the acceptable quantitative value of wear.