Constant surface roughness over tool-lifetime due to online process monitoring and cutting parameter adaption in turning of gear steel

High process forces and temperatures in turning operations cause high tool wear rates. Tool wear such as flank face abrasion has direct impact on workpiece geometry and resulting surface roughness. Since tools are used until tool life criterion is reached, surface quality can vary widely over the workpiece even when constant cutting parameters are utilised. A measurement system based on laser triangulation has been developed which enables the online measurement of surface roughness on the workpiece during the turning process. Using the online surface roughness measurements, closed-loop controllers were developed in order to adapt the tool feed and the cutting velocity to retain constant surface roughness even when tool wear is progressing. An optimised process with constant cutting parameters was benchmarked to the developed processes with adaptive cutting parameters. It can be shown that parameter adaption has the potential to lead to efficient processes and increases the tool-lifetime TToollife significantly.