Gear Skiving - A Step Changing Manufacturing Process Applicable to Multifunctional 5-Axis Machine Tools

摘要

The gear skiving cutting process is a machining method applicable to producing both internal and external gear teeth. The process is known to have significant productivity advantages over shaping, and when compared to hobbing, the tool demands less clearance and therefore has the advantage of being able to machine in close proximity of shoulders. Despite only becoming an area of prevalent interest within the gear industry in recent years, the gear skiving method for gear cutting was first patented in 1910 (Ref.1). The process demands a high degree of synchronization accuracy between the workpiece spindle and the tool spindle, as the two mesh together, similarly to a pair of gears at increasing depths to create the gear form. As stated by Weppelmann, "Machines and cutting spindles simply weren't robust and rigid enough to minimize vibrations caused by the high spindle rpms and significant cutting forces generated by the skiving process" (Ref.2). However, as machine tools and their capabilities have improved, bespoke gear skiving machine tools have been manufactured. The AMRC has been keen to pursue the capabilities and performance of generic multifunctional machine tools such as those that are already in use on many factory floors, when faced with the gear skiving cutting cycle. The main benefits of performing the gear skiving process on a multifunctional machine tool include smaller manufacturing cells, reduced capital expenditure, and the potential for an increase in dimensional accuracy of components, as the gear form can be generated in the same setup as the majority of other turned/milled features. Sandvik Coromant AB state that "Advances in machining centers have paved the way to a more productive process for producing internal gears - gear skiving. This faster process offers improved quality at lower cost and is four to ten times more productive than, for example, shaping. It also gives better flexibility and quality than broaching. Consequently, machine tool manufacturers are now developing machining centers and software solutions capable of dealing with the specific requirements of the process" (Ref.3). The medium-long term aim is to use the gear skiving process to both rough and finish gears. Whilst in the short term, it is more feasible to assess gear skiving as a roughing process only, where the gears would undergo a secondary finishing operation such as grinding after case hardening.