Papers by Author: Xiao Hu Zheng

Abstract: In recent years, micro-machining has obtained increasingly attention and been more and more widely used in the field of machining. As a vital important aspect in the design of micro-tool, traditional tool geometry design methods need to be improved. In this paper, the mathematical model of D-type micro end-mill is developed; FEM analysis using ABAQUS 6.12 is employed to optimize the geometry parameters of D-type micro end-mill, which is proved to be a very convenient method. For small diameter tools, strength is the primary factor to be considered in their design, so the target of optimization is to minimize the maximum principal stress and deformation of the micro-tools.

Abstract: Drilling procedure is widely used in orthopedic surgery to insert the steel nail to stabilize the bone. However, successful execution of bone drilling requires a high level of dexterity and experience, because the drilling resistance is large and sometimes vibrates violently to even break the slender drill. This paper introduces the study of drill force in different cutting parameters and different bone density. The density of cortical bone is higher than that of cancellous bone, so the drilling force decreases suddenly from the peak and then maintains a stable value. Drilling forces are more related with feed speeds and bone density. Drilling force increases as feed speed increases and bone density increases. Accurate drilling process can be obtained to provide effective surgery training and rehearsal.

Abstract: This paper investigates the effects of MQL system on the grinding performance of Ti-6Al-4V using SiC abrasive, the evaluation of the performance consisted of analyzing the grinding force, surface roughness and surface morphology. The experiment result indicated that the favorable lubricating effect of MQL oil makes it has the lowest value of grinding force, specific energy and force raito. MQL has better surface finish than dry grinding and fluid grinding has the lowest value of surface roughness under different grinding depth. Surface damages such as: side flow, plastic deformation, redeposition are present in dry and fluid grinding. As grinding depth increased, the damages become much more severe. But in MQL condition, it gives better surface integrity than dry and fluid grinding.

Abstract: High cutting force, high cutting temperature and severe adhesion will be produced in the machining process of Ti-6Al-1.5Cr-2.5Mo-0.5Fe-0.3Si. Furthermore, there are critical needs to reduce the use of cutting fluid in machining process. This paper presents a friction force model under MQL condition. An experiment of turning titanium alloy was presented to test and analyze MQL effects. The mainly results were: (1) MQL can reduce the friction at the chip-tool interface when cutting parameters and matching parameters of MQL were chosen properly. (2) Degrees of serrated chips and chip morphology affected by different lubrication conditions were different.

Abstract: Microburrs have great influence on printed circuit board’s quality. PCB is composed of glass fiber plastic reinforcement material and copper foil. The PCB microburrs are generated in copper foil drilling process. These burrs are generated by copper extrusion and accumulation around the micro-hole. Enter burr and exit burr is quite different. Enter burrs are lower than exit burrs. The burr formation experienced three stages: First, Copper foil extrudes with the feed of microdrill; Second, Most of the Materials are cut off by drill tip and the rest of material; At last, rollover burrs appear when drill enters or exits uncut chip rolls.

Abstract: Tool breakage monitoring is crucial to automation fabrication, especially for high-density hole machining, such as PCB (Printed Circuit Board). A tool breakage feature extraction method in PCB micro-hole drilling is presented in this paper. The vibration signal is analyzed by wavelet transform. The decomposed signals energy ratio at each frequency band is computed as monitoring features. The monitoring performance of different features selection is given. The vibration signals are observed to provide the capability in distinguishing micro drill breakage with proper features extraction and classifier design.

Abstract: Printed circuit board (PCB) composed of glass fiber reinforcement plastic and copper foil is a kind of typical composite material. The cutting process of fiber reinforcement plastic materials such as carbon fiber or glass fiber reinforcement plastic materials have been studied for many years, but the drilling process of printed circuit board using microdrill is more complicated than common carbon fiber reinforcement plastic materials. It is event that the cutting force changed when drill different material. The variation of drilling force may cause some problems such as drill break, board delamination. So it is important to study the drilling force in PCB drilling. The precision dy-namometer was used in experiments and cutting process was analyzed in this paper. The drilling process of PCB experience six stages and the drill will meet aluminum board, glass fiber reinforce-ment plastic (GFRP) and base strip. According to the drilling force in one circle, the peak force ap-peared at the moment of drilling copper foil and another smaller peak force appeared at the moment of drilling aluminum board and base board. The experiment results show that thrust force increased with federate and decreased with rotational speed.

Abstract: In recent years, with the development of machinery industry, micro-cutting technologies have been gradually moving into engineering realization. The paper carries out a series of works on simulation modeling of micro-cutting of Ti-5Al-5V-5Mo-3Cr considering tool edge radius. Unlike conventional cutting, in micro-cutting the effect of tool edge radius which has a marked impact on cutting force, specific cutting energy, burr formation and burr size can no longer be neglected.

Abstract: This paper investigates the surface grinding of Ti-6Al-4V under minimum quantity lubrication (MQL) condition. The experiment result indicated that grinding force ratio and specific energy have close related to grinding parameters. Due to the flow field of MQL mist has easy been affected by feed rate, the interaction between of MQL mist flow field and feed rates of worktable has great effect on surface roughness and surface quality. Additionally, comparing to dry grinding, MQL could help to improve surface quality by restrain chemical reactions and physical changes.

Abstract: Titanium alloy is widely used in aerospace and aircraft industries but it is a kind of difficult-to-cut material. In this paper, wet grinding and dry grinding of titanium alloy Ti-6Al-4V using green silicon carbide wheel were investigated. The specific tangential force and force ratio were calculated and surface roughness of machined surfaces was measured. The morphology of machined surface were observed by SEM. The experimental results showed that the specific tangential forces were big. The depth of cutting has greater influence on surface roughness than workpiece speed. The surface roughness of wet grinding was better than dry grinding. Micro cracks were observed on wet grinding. The main reason is the high temperature and quenching cracking.