Chapter 11 Variants of high speed machining
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| 296 High speed machining demonstrated that in the case of the blade wear > 0.2 mm, an increase occurred in the residual stress size and depth of penetration into the workpiece material, which affected fatigue performance. A less positive tilt angle and a higher edge wear length caused an increase in burr height. In the optimization phase of the test program, it has been determined that the cutting speed is the machining parameter having the maximum effect on tool performance regarding material lifting. At a worn length of 200 m, the material mass was removed at the cutting speed of 2000 m/min ∼5 kg. In case of higher cutting speed, the resulting mass of material was ∼2 kg. The same figure shows typical wear mechanisms that were recorded in the earlier-mentioned phase of the experimental program. It is possible to state that the higher cutting speed has no adverse effect on the wear mechanisms. Furthermore, the amount of the pasted workpiece material was decreased at 5000 m/min in comparison with 2000 m/min. During machining at lower cutting speed, an increase takes place in the contact time of the tool with the workpiece material. This can possibly explain a higher amount of workpiece material bonded to the flank face at 2000 m/min Despite the fact that aside wear area of 0.3 mm was the standardized limit for the retired team, the experiments carried out in this research were terminated at aside wear limit of about 250 m because of the significant deterioration in burr formation and the quality of the machined surface. While machining using a sharp tool (edge wear <10 µm), no burrs were determined along the edge of the feature. However, with a used vehicle, the rollover burr was identified. In case of utilizing a worn tool, the tool/workpiece interface and the temperature generated throughout the plowing force increase. The workpiece material’s ductility will be increased by the higher temperature produced, and a higher mechanical load on the workpiece material will be created by the friction force [34] The second category, the aircraft sector, generally includes the processing of thin-walled high aluminum and titanium alloy parts. The design of aircraft structures is realized in such a way that they are com- posed primarily of integrated elements manufactured as a result of welding or riveting of parts in technologies previously used in the manufacturing process. It is possible to categorize parts, including ribs, necks, beams, frames, hull body, and blades, as integral elements [35] . Following machining, the parts in question are mounted on larger assemblies. The main aim of the operations used is to en- sure the functional criteria and the best strength ratio to the strength value. The use of high milling speeds reduces the processing time, enabling the economic manufacturing of integrated components and also enhancing the quality of the machined surfaces. This is because there are considerably lower cutting forces for higher cutting speeds in comparison with standard machining methods. The usage of high speed milling technology for machining thin-wall aircraft frames is possible depending on the workpiece precision and the machining capacities of the 7075 aluminum alloys. The choice of proper cutting parameters provides good surface roughness and ripple [35] |