Development of a Generic Tool Condition Monitoring Validation Methodology

This research brings GMP validation techniques to bear on a system that monitors the tool wear aspect of CNC machining, known as Tool Condition Monitoring (TCM), with a view to improving the overall performance of the process. The work was carried out in tandem with an EU FP7 funded project which installed force, acoustic and vibration sensors on CNC machines in Ireland, Poland, Italy and Norway. The validation techniques are focused on the medical devices sector, primarily because the medical devices sector is bound by Good Manufacturing Practices (GMP’s), which are mandatory regulatory requirements. GMPs are enforced in different parts of world by different regulatory bodies; some of the more recognizable bodies would be the U.S. Food and Drug Administration (FDA), the World Health Organization (WHO) and the European Union (EU). Validation is an essential part of good manufacturing practices and the approach of bringing GMP validation techniques to TCM has not yet been implemented in this industry, which otherwise relies heavily on validation. The validation process consists of identifying and testing all aspects of a process that could affect the final product. A validated process is one which has been demonstrated to provide a high degree of assurance that uniform batches will be produced that meet the required quality specifications throughout the product lifecycle. One of the unique elements of this research was the incorporation of a Case-Based Reasoning (CaBR) control system into the TCM, and the application of the validation model to CaBR, an area which has received little attention in literature. The system must be trained by a machine operator, during the setup process, to identify when a tool is at end of life and based on this data makes its own decisions around the degree of tool wear present on the tooling. Validation of the CaBR system was completed by establishing whether an individual test case had been solved correctly, through benchmarking against learned information and operator expectation. The REALISM TCM system was tested in accordance with regulatory requirements and has passed testing for the turning operation, boring operation and detection of catastrophic tool failure (CTF), the drilling operations however, failed validation testing.