Five-axis machining is necessary to produce precise and high quality free form surfaces for metallic products such as gas turbine impellers. Manufacturing processes before machining, such as casting or forging, in addition to the recently developed metal additive manufacturing processes often leave surfaces with poor finish, undesirable metallurgical structure and inaccurate geometry. In particular, the surface finish is often poor with various additive manufacturing methods, particularly in the wall directions compared to the surface generated at the build direction. With few alloys, it is possible to improve the surface finish by chemical machining approaches, but in many other alloys, a finish milling operation is often necessary to remove the rough and sometimes defective sub-layer and possible build support features. Majority of AM manufactured components are already “topologically optimized” and they are manufactured near net shape and may offer limited stiffness compared to those machined from solid billets or forged pieces. Furthermore, while in past the finishing was dominated by ball-end milling operations, recently complex cutting edge geometries are developed that provide better surface finish by cutting along a longer curved cutting edge compared to ball-end milling.An example is a design, which is often referred to as “Barrel-End” mill, which with a large engagement length can produce a better surface finish compared to a ball-end mill that machines the surface in more passes. On the other hand, the large engagement with the workpiece can lead to regenerative vibrations (known as chatter) between the tool and the workpiece. Since the finish milling can often be accomplished by a wide selection/combination of overlap, depth of cut, tilt and lead angles, it is deemed valuable to study and develop guidelines and algorithms, both in cases where vibrations originate from the flexibility of the workpiece and also in cases where the instability is originated from the flexibility of the spindle-tool combination. Modern tools can also have unequal spacing between their teeth and/or variable helix angles to improve their stability. Correspondingly they need more sophisticated algorithms in modelling. This project will use tools and methods that are developed during previous projects at University West, such as machine tool encoder signal processing system, in processing its experiments, and CNC data streaming capabilities, along with in-process spindle dynamics identification methods, to predict and optimize various parameters that could be selected for five axis finish-machining where dynamic flexibility of the tool or the workpiece can cause unstable vibrations. The co-produced results will be packaged as user-friendly calculation tools and educational courses to be offered to a wider number of employees within the participating companies. The proposed project includes work packages for geometrical modelling, stability modelling, in-process identification along with verification and industrial case studies. The project will also be executed in collaboration with Industrial Work Integrated Group from PTW.
Avverkande och additiva tillverkningsprocesser
Forskningsmiljö / Institution
Produktionsteknik Väst, PTV
Institutionen för ingenjörsvetenskap