Papers by Author: Yue En Li

Abstract: The error due to tool deflection is detrimental to machining precision. In order to predict tool deflection more accurately, this paper presents a special three segments cantilever beam model for ball-end tool deflection in sculptured surface milling. Different from the traditional two segments cantilever beam method, the ball-end tool is divided into the shank, the flute and the ball-end parts in this new model. Then the ball-end tool deflection is simulated also by utilizing the finite element software ANSYS 12.0 Workbench to calibrate the accuracy of the tool deflection models. The three segments cantilever beam model for ball-end tool deflection matches better the finite element method (FEM). In the last part of the paper, the sculptured surface machining experimental results show that, the surface precision after tool deflection compensation based on the new three segments cantilever beam model is higer than that based on the two segments cantilever beam model.

Abstract: In this paper, the effects of the variational combinations of cutter inclination angle in feed direction and the feed per tooth on the machined surface hardness were mainly concerned. The cutting forces transformed from the measured cutting forces in OXYZ and the SEM microstructures of the surface layer were analyzed to explore the generation condition of the hardness. Variations of the surface hardness are not apparent with the increment of feed per tooth with the identical other cutting parameters. Inclination angles in feed direction of approximately ranging from 10° to 15° and from 25° to 30°, which correspond to high surface hardness, are suggested to be applied in cutting process when high abrasive resistance is expected. While values of inclination angle approximately equal to 0° and 45° are prior to be chosen when high shock resistance performance is firstly expected. Optimization of the cutting parameters, which could offer guidance to the machining of sculptured surface concerning cutter inclination angle, was presented.

Abstract: This paper explores the wear mechanisms of a Sialon ceramic tool in ultra high speed turning of Nickel-based alloy Inconel 718. Microstructures of the chips are also investigated. Stereo optical microscope and scanning electron microscope (SEM) are employed to observe worn surfaces of the tool produced by various wear mechanisms and morphological features of chips. In addition, the elemental compositions of wear products are evaluated by energy-dispersive X-ray spectroscopy (EDS). As a result of the study, wear mechanisms identified in the machining tests involve adhesive wear and abrasive wear. At the initial stage of cutting process, crater wear and flank wear are the main wear patterns. At the rapid wear stage, the SEM and EDS results showed that the adhered elements of Inconel 718 alloy on the tool rake face such as Ni, Fe and Cr accelerated the tool wear rate. Meanwhile, it was found that the chip morphology was serrated type under ultra high speed cutting condition, furthermore, the tendency of serration of the chip increased with the increase in cutting speed and feed rate.

Abstract: The main purpose of this study was to construct a relationship between the cutting parameters and the machined surface on high speed milling operation. An optimization algorithm using an Exponential Equation and BP method (EEBP) is then applied to determine optimal cutting parameters. For using the method, once the material removal volumes for machined parts of the high speed milling operations are given, the surface quality could be predicted. The final result we choose the surface roughness prediction as an example of H13 dies steel HSM in this paper, it presents that the method is efficient and feasible.

Abstract: High speed milling experiments are performed for hardened H13 die steel by using coated ball end milling cutter, the residual stress of the work-piece surface on the feed and cross feed direction are measured, and the distribution characteristics of residual stress is analyzed. The result shows that the residual stress presents gradient distribution on feed direction, and furthermore, the three-dimensional surface micro topography has no close relation with the residual stress. In addition, the cumulative effect is discussed for explaining the phenomena.

Abstract: Complex surface mold has been widely used in various industries, and high efficiency and high quality can been achieved through high-speed CNC milling processing. Surface roughness including transverse and longitudinal roughness is an important criterion for mold quality. A high-speed milling experiment was performed in mold steel P20 using cemented carbide ball-end mill to investigate the surface roughness. The effects of process parameters on roughness including spindle speed, feed per tooth and radial cutting depth were examined, and an analysis on the mechanism for two kinds of roughness of different tool paths was finished. The experimental results show that the longitudinal roughness improve obviously while the spindle speed and the feed per tooth increase on the high-speed conditions, and the transverse roughness increase significantly when the radial cutting depth increases. And for a smaller roughness value, the tool path should be selected along the direction in which the curvature changes evidently.