Laser Remanufacturing and Reconditioning of Cutting Tool Inserts

The cutting tool industry has yet to fully embrace the circular economy to extend tool life. The repair of cutting tools can allow the extension of tool life, to extract the maximum value of resources. It acts as a restorative process that can prevent the tool material being wasted. This is a significant gap in the tooling industry. Therefore, this research aimed to develop a laser remanufacturing and reconditioning (LRaR) strategy to restore the condition of cutting tool inserts after wear damage. The result of this research is promising in improving sustainability practices, by investigating how the repair of cutting tools can be integrated into current manufacturing practices. Repair can be broken into 2 main types: remanufacturing and reconditioning. Remanufacturing brings the tool to higher or original quality and reconditioning brings the tool to original or usable quality. Despite the benefits of tool repair, the introduction of repair presents many challenges, barriers and little work has been conducted in this field. This research explores the development of stages to create a laser-based repair for tool inserts, this includes tool wear detection, laser processing optimisation, standardisation of the repair process, and testing the performance of repaired tools.

The first stage of the LRaR process developed was a direct in-situ 2D tool wear detection (ITWD) system, to measure tool wear characteristics within a lathe environment. It was an algorithm-based machine learning model trained for tool wear detection and integrated with appropriate hardware, which was critically tested and evaluated. Key wear characteristics were measured and easily extracted and efficiently outputted to the user, to a high detection and measurement accuracy, greater than 95%. It was the first demonstration of an in-situ 2D wear method for turning inserts that is also based on open-source cloud-based software using accessible equipment. The extraction of the wear characteristics was used to inform and tailor the repair to the specific wear damage on the tool.

The second stage of the LRaR process was to optimise the repair method. The repair method chosen was pulsed laser ablation (PLA). PLA was selected as it was capable of precise machining of hard and ultra-hard materials. Optimisation of PLA parameters, tool grades and characteristics created distinct microstructures that featured specific surface and mechanical integrities. Analysis of the results defined 6 independent PLA strategies suitable for tool repair including the removal of wear damage and modifications to the tool edge. These strategies were: PLA roughing, PLA milling, PLA near-net shaping, PLA grinding, PLA grinding for specific surface roughness and PLA polishing. The parameters to create each strategy was mapped for the repeatable generation of these strategies in a range of tool grades and laser systems. The PLA strategies showed great potential for laser-based repair to be a fast, multipurpose, and bespoke method.

The combination and digitalisation of the ITWD and PLA repair strategies was the third stage of the LRaR process which selected the ideal PLA repair strategy based on the input wear to output a laser path. A program was developed to standardise and automate the generation of a laser repair g-code. Key stages of the laser process setup, tool repair and post processing were structured into a template to allow the g-code script to be bespoke to input wear damage. Once generated, the g-code was used to repair 72 worn tool inserts. The program streamlined the process of laser repair by featuring clearly defined steps with reduced variability in the process in an open-source cloud-based platform.

The fourth stage of the LRaR process was to validate and characterise the repaired tool insert. The performance of the LRaR repaired tools was then assessed to compare the functionality to benchmark tools. Cutting metrics were used to measure cutting forces, friction, tool chip interactions and chip characteristics. The results showed that the repaired tools had a good quality cut performance and held up well against the benchmark tools, with the majority of the tools being remanufactured (86%) and some tools being reconditioned (14%). The results confirmed the LRaR process was a viable option for tool repair enabling it to be an acceptable form for tool life extension. The acceptable performance deviation was also able to be defined against current ISO standards. By setting threshold performance indicators to categorise the quality of repair. In addition, to a practical validation of the LRaR process, the LRaR process was compared to the existing methods of repair against technical and economic factors. This acted a validation from a decision-making criteria standpoint. The LRaR process was on par with current methods and meet the key factors needed to carry out tool repair. Finally, the thesis reviewed the results obtained during the research, the contributions to industry and recommendations for future work to continue the improvement of the circular economy in manufacturing.