Realization of ductile regime machining in micro-milling SiCp/Al composites and selection of cutting parameters

SiCp/Al composites are widely used owing to their outstanding performance. However, due to the existence of brittle SiC, surface defects caused by particle fracture damage the surface quality severely. Meanwhile, due to small cutting parameters during the micro-milling process, especially the undeformed chip thickness, which is mainly determined by the feed per tooth, the size effect of matrix also damages the surface quality. In this study, a method by realizing the ductile regime machining of the particle and diverting away the defects of particles and matrix is proposed to select the cutting parameters and improve the surface quality in micro-milling SiCp/Al composites. Suitable range of values of the feed per tooth for side milling and end milling are obtained by this method and validated by micro-experiments. The results show that the size effect of Al and removal ways of the SiC particles affect the machined surface simultaneously. By using suitable feed per tooth, weak size effect of Al and most of the particles’ ductile regime removing can be realized, leading to the generation of the best surface. Additionally, the machining effects of this method are more prominent in end milling than in side milling.

Achievement of Ductile Regime Machining in High Speed End Milling of Soda Lime Glass by Using Tungsten Carbide Tool Insert

Soda lime glass is widely used in optics, chemical apparatus, camera lens, micro gas turbines, light bulbs etc. on account of its high hardness, corrosion resistance, and excellent optical properties. These require high dimensional accuracy and flawless surface finish. However, soda lime glass is inherently brittle leading to subsurface crack propagation and fracture which compromise its functionality. To avoid these defects, the machining needs to be performed under ductile mode conditions. Therefore, this research investigates the viability and requisite conditions for achieving ductile regime machining (DRM) in high speed micro-end milling of soda lime glass. Machining was performed at high cutting speeds (30,000 to 50,000 rpm), feed rate (5 to 15 mm/min), and depth of cut (3 to 7 μm). A surface profilometer was then used to measure the surface roughness and a scanning electron microscope (SEM) used to scrutinize the resultant machined surfaces. The results demonstrate that ductile streaks and rounded gummy chips (without sharp or jagged edges) are produced in all runs. In addition, there are no subsurface cracks and the minimum surface roughness attained is 0.08μm. These indicate that DRM of soda lime glass is obtainable using high-speed micro end milling in a conventional end mill with tungsten carbide inserts.

Effect of Cutter Diameters on Surface Roughness Attained in High Speed End Milling of Soda Lime Glass

Soda lime glass is used extensively in camera lens, micro gas turbines, light bulbs, tablewares, optics, and chemical apparatus owing to its high hardness, excellent optical properties, and good corrosion and chemical resistance. Such applications of soda lime glass demand high machining and finishing precision. On the other hand, machining of glass poses significant challenges due to its inherent brittleness. The process of removal of material from glass, if not done in ductile mode, can generate subsurface cracks and brittle fractures which have adverse effects on its functionality. This research investigates the high speed micro-end milling of soda lime glass in order to obtain ductile regime machining. It has been found by other researchers that ductile mode machining can avoid sub-surface cracks and brittle fractures. However, in ductile mode machining, the gummy chips settle permanently on the machined surface affecting adversely the surface finish. In order to avoid such chip settlement, compressed air was directed using a special air delivery nozzle to blow away the resultant gummy chips, thereby preventing them from settling on the machined surface. Response surface methodology (RSM) and a commercial NC end mill were used to design and perform the machining runs, respectively. Machining was done using: high spindle speeds from 30,000 to 50,000 rpm, feed rates from 5 to 15 mm/min, and depth of cuts from 3 to 7 μm. Three different diameter carbide tools were used: 0.5, 1, and 2 mm. A surface profilometer was used to analyze the surface roughness of the resultant machined surface. Subsequently, the data was used for finding the best combination of cutting parameters required to obtain the lowest surface roughness. The results demonstrate that high speed machining is a viable option for obtaining ductile regime machining and generating machined surfaces with very low surface roughness in the range of 0.08μm – 0.22 μm, using 0.5 mm carbide end mill cutter.