An Investigation on the Suitability of Abrasive Waterjet Cutting for Hybrid Manufacturing of Gears in Automotive Industry

Sammanfattning: Gears are components in mechanical assemblies used for transmitting power and motion. Gear form cutting (broaching, milling) and gear generating (shaping and hobbing) are two of the main gear manufacturing methods. Usually production involves three stages: (i) soft machining, (ii) heat treatment, and (iii) hard machining. Limitations introduced by conventional methods can be listed as follows: - In machining difficult to cut materials, high cost of specialized cutting tools, high cutting tool failures is a major issue and high cost of machine tools. - Stresses generated due to heat (thermal stresses) and cutting force affect the component life and cost. This demands alternative ways of material removal without affecting the mechanical properties while delivering right quality in a cost effective way which is the goal of the industry. - Increasing standards on environmental impacts associated with products force the modern manufacturing industry to take critical approach on making processes environmental friendly. Large volume of material is removed during conventional gear production resulting in higher lead time, more use of cutting fluids (and its disposal), chip handling (and its disposal) and dust. In this context, abrasive waterjet (AWJ) cutting is considered to be a good addition to the current production system due to the low amount of applied force, negligible heat generated during machining, minimal change in material properties, versatility, lower initial investment and environmental friendliness (no chip generation and no need for cutting fluids). To demonstrate the capability of the proposed approach in manufacturing spur gears and helical gears, forged gear blanks typically used on automobile industry were used for initial tests and two gears were produced using 3-axis KimTech and 5-axis FineCut precision AWJ machine tools. Individual teeth have been separated from each gear and tested against each other from different perspectives. The metrological, surface integrity, productivity and production cost comparisons were presented.While improvements were achieved from environment and surface integrity perspectives, AWJ cutting cannot replace soft machining stage due to increased lead time and production cost. Novel hybrid gear manufacturing method was proposed from the experiences from this research and compared against the conventional method employed in the automotive industry. Proposed hybrid approach comprises AWJ cutting process as the major material removal method and conventional 5-axis machining for final finishing or maintenance of tight tolerances and at the same time, decreasing initial investment and adding further flexibility to production system.This publication is part of my research work at KTH Royal Institute of Technology, thanks to a Swedish Institute scholarship.