Papers by Keyword: Surface Quality

Abstract: The traditional magnetic abrasive finishing (MAF) process, the magnetic flux density at the bottom of the magnetic pole is unevenly distributed, resulting in poor uniformity of the finished surface. Therefore, it is proposed to improve the surface quality by attaching a magnetic plate at the bottom of the workpiece to improve the magnetic field distribution. It is confirmed by simulation that the magnetic field distribution at the bottom of the magnetic pole is effectively improved after the magnetic plate is attached. It is proved through experiments that the magnetic plate-assisted MAF process can obtain a smoother surface. The experimental results show that the surface roughness of the glass lens improves from 246 nm Ra to 3 nm Ra through the magnetic plate-assisted MAF process within 45min.

Abstract: In this paper, a series of chemical mechanical polishing (CMP) experiments for magnesia alumina (Mg-Al) spinel were carried out with different abrasives, and the materials removal rate (MRR) and surface quality was evaluated to explore their different effects. The scanning electron microscope (SEM) and laser particle size analyzer were also employed to test the micro-shape and size distribution of abrasives. Then, the mechanism of different effects with different abrasives was analyzed in CMP for Mg-Al spinel. Those experimental results suggest that different subjecting pressure ratios of abrasives to polishing pad with different abrasive are the key factors leading to difference polishing performances in CMP.

Abstract: This study investigated the effect of laser power (P), scan speed (v) and hatch space (h) on densification behavior, surface quality and hardness of 18Ni300 maraging steel fabricated by selective laser melting (SLM). The results indicated that the relative density of the SLMed samples has a shape increase from 73% to 97% with the laser energy density increasing from 0.5 to 2.2 J/mm². The relative density ≥ 99% was achieved at the energy density in the range of 2.2~5.9 J/mm². The optimum process parameters were found to be laser power of 150~200 W, scan speed of 600mm/s and hatch space of 0.105mm. In addition, it was found that the hardness increased initially with the increasing relative density up to relative density of 90% and then little relationship, but finally increase again significantly. This work provides reference for determining process parameters for SLMed maraging steel and the development of 3D printing of die steels.

Abstract: In this research, the four-ball tribometer was examined to evaluate the tribological behavior of environment-friendly nano-MoS₂ water-based rolling liquid. This experimental method is used to measure the maximum non-seizure load (P_B) and the coefficient of friction (μ). The newly introduced parameter ω can be combined with P_B and μ to evaluate the tribological performances of the rolling liquid comprehensively. The rolling lubrication performance of nano-MoS₂ water-base lubricant was investigated using a single stand 4-high reversing rolling mill. The surface morphologies and rolling textures of the samples were measured by laser scanning confocal microscope after cold rolling. The results show that when the concentration of nano-MoS₂ is 0.4wt.%, the water-based rolling liquid has excellent tribological and lubricating properties. Meanwhile, compared with the surface quality of the rolled strip under other lubrication conditions, the surface quality of the cold-rolled strip using 0.4wt% nano-MoS₂ rolling liquid as the lubrication condition is smooth without visible surface defects.

Abstract: Selective Laser Melting SLM is one of the most popular three dimensional printing methods, which can be used for manufactured real elements (with high geometrical complexity) in many application, such as medicine, automotive or aerospace industries. The SLM final parts are characterized by high mechanical properties and satisfactory physicochemical properties. However, the properties of parts depend of process parameters optimization. In this paper, effects of processing parameters, such as laser power P, scanning speed SP, layer thickness t or point distance PD on defect formation and relative densities of manufactured elements are explored. For the purpose the stainless steel 316L and pure titanium Grade II are used. The process optimization were carried out according to the formula of energy density, which is delivered to the powder material. The stainless steel samples were divided into 12 groups, depends of the energy density. The titanium parts were printed at the same value of energy, and the process parameters are changed. The microscope observation and relative density measurements were carried out. Based on the obtained results, it can be confuted that the SLM parameters have a significant effect on the samples properties and the mechanism formed defect in both material are similar.

Abstract: The problem of round-rolled surface products improving quality by reducing roughness and waviness is solved. Traditionally, grinding is used to improve the surface quality, but at the same time new defects appear in the form of cracks, tinge colours and the abrasive particles in-filtration into the surface layer. Surface pressure processing instead of grinding is not associated with such defects, therefore, it is proposed to use a transverse rolling. Rolling rational profile for transverse rolling on round-rolled surface was theoretically determined. Analytical dependences were obtained for rolls in cage with support rings calibration calculations. Such calibration use ensures uniform deterioration of roll and rings bearing surfaces, as well as the rolls balance with their one-sided load during rolling. A parametric analysis of the deformation conditions effect on the rolls geometry was performed. The conditions under which rolls profile can be limited to a circle or a straight line were considered. The obtained results were used in rolls profiling for drawing the rolling surface in laboratory and industrial conditions.

Abstract: BK7 optical glass has been widely used in modern high-tech fields such as aerospace, automotive, optical precision instruments, electronic information, etc. due to its excellent performance, but its gap between plasticity and hardness is huge, making traditional machining easy to appear sub-surface. Damage and other phenomena, surface quality is difficult to meet the requirements. In this paper, the ultrasonic milling dynamics model was firstly established, and then the multi-factor method was used to detect the longitudinal torsional composite ultrasonic milling and ordinary milling of BK7 optical glass, and the surface roughness and surface topography of different spindle speed, milling speed and milling depth were analyzed. Finally, the laws and mechanisms affecting the quality of the machined surface were obtained. It is found that the surface quality is best when the spindle speed is 3000r/min and the milling depth is 0.2mm; the surface quality of BK7 optical glass decreases with the increase of milling speed. The surface quality and processing efficiency of BK7 optical glass are improved by longitudinal torsional composite ultrasonic vibration milling, and the optimal process parameters for BK7 optical glass longitudinal torsional ultrasonic milling are provided.

Abstract: In this paper, the impact of cutting speed and feed amount on cutting deformation and surface quality and cutter wear have been studied by the test of high manganese steel cutting with metal ceramic tool at high speed. The results show that it is feasible by cutting high manganese steel with cermet tool at high-speed cutting (HSC). Chip changes into succession segment from band in macrostate. Sawteeth can be seen on the top surface of chip while high temperature feature in burning color and cold welding form appear on the bottom of the chip. The model of surface roughness built can be used to predict surface quality at HSC, and provided cutting optimized parameters scheme. Further research indicates that high-speed cutting has its special deformation mechanism and plastic chips exhibit hot brittleness which provides a favorable condition for solving the chip breaking problem in the cutting of high manganese steel.

Abstract: The paper provides the results of experimental studies of changes in the depth of the defective layer during milling of various structural materials; shows the convergence of the experimental results with the data published in open-access publishing; substantiates a logical change in the depth of the defective layer at various stages of multi-stage machining; and builds probabilistic tables of milling accuracy.

Abstract: This paper provides a methodology for continuous computer support of technological quality assurance for assembly units based on automated subsystems to conduct a dimensional analysis for the main life cycle stages allowing technological, assembly and operational dimensional relations in machines construction to be analyzed.