Cheng Yong Wang

Polishing of ceramic tiles

Grinding and polishing are important steps in the production of decorative vitreous ceramic tiles. Different combinations of finishing wheels and polishing wheels are tested to optimize their selection. The results show that the surface glossiness depends not only on the surface quality before machining, but also on the characteristics of the ceramic tiles as well as the performance of grinding and polishing wheels. The performance of the polishing wheel is the key for a good final surface quality. The surface glossiness after finishing must be above 20° in order to get higher polishing quality because finishing will limit the maximum surface glossiness by polishing. The optimized combination of grinding and polishing wheels for all the steps will achieve shorter machining times and better surface quality. No obvious relationships are found between the hardness of ceramic tiles and surface quality or the wear of grinding wheels; therefore, the hardness of the ceramic tile cannot be used for evaluating its machinability.

Drilling Force and Temperature of Bone by Surgical Drill

Drilling force and temperature of tibia at the high speed drilling for improving the design of surgical drills are very important. In this paper we describe experiments using pig tibia bones, measuring the drilling force and temperature of a new design of drill bit and compare the results against a twist drill. The result shows that the drilling force and temperature are affected by the feed rate and drilling speed, which vary with the drilling depth into the bone. The new surgical drill with three top cutting edges can achieve lower temperature below 47oC and lower drilling force than with the stainless steel twist drill and carbide twist drill.

Experimental study on micro-drills wear during high speed of drilling IC substrate

Purpose – Compared with the traditional printed circuit board (PCB) drilling process, the technology of drilling IC substrate is facing more problems, such as much smaller hole diameter, more intensive hole space, thinner sheet and more complicated materials are drilled in process. Moreover, the base material of IC substrate is different from traditional PCB, more kinds of fillers added in IC substrate which make the drill worn seriously during drilling process. Micro-drills wear and micro holes quality are the most important questions when drilling IC substrate so far. Wear morphology of micro-drill, holes wall roughness and hole location accuracy are researched in this paper. The influence factors of micro-drills wear and micro holes quality are also studied in this drilling process. The paper aims to discuss these issues. Design/methodology/approach – Two drills with same structure and different diameter are used to drill different stacks of IC substrate and drill different holes in this paper. There a...

Drilling Force and Chip Morphology in Drilling of PCB Supported Hole

Supported holes of Printed circuit board (PCB) are drilled with two different drill bits. Drilling force (thrust force and torque) and chip morphology are examined at different cutting parameters, and the effects of the two drills are discussed. The results indicate that the drilling force and chip morphology are affected by the feed rate, spindle speed and drill shape. Thrust force increases with the increasing feed rate, and decreases with the increasing spindle speed. Optimization of drill geometry can reduce the thrust force significantly, and is effective in chip breaking which can improve the chip evacuation during the drilling process.

A Review on Drilling Printed Circuit Boards

Drilling is a particularly complicated machining process, and it becomes much more complicated when the workpiece is printed circuit boards (PCBs). PCB is composite materials with anisotropy. Even a small defect in PCB may cause great losses. Both the drilling process and PCB structure design have been researched by many scholars. But the investigations into the drilling processes of PCB are not systematic. The present review article address the report about tool materials and geometrics, cutting force, cutting temperature, radial run-out and damages occurring in drilling processes. And as a conclusion, some of these critical issues are proposed to meet the challenges in analysis and optimization for PCB drilling.

Hole Machining of Glass by Micro Abrasive Suspension Jets

Abrasive Suspension Jets (ASJ) is a new micro processing technique developed for micro processing of hard and brittle materials based on the traditional Abrasive Water Jet (AWJ). Based on drilling experiments of glass using MASJ technology, the dependence of material removal, the depth and the diameter of the machined holes on the process parameters, such as working pressure, processing time, standoff distance, incidence angle and concentration of abrasives were investigated. Experimental results show that the material removal is approximately proportional to working pressure, processing time and concentration of abrasives, except the standoff distance. It is founded that the processing time is the most remarkable influence factor on the material removal and the depth of the holes. But the working pressure doesn’t show obvious effects to the material removal and the depth of hole with lower pressure in MASJ. The increase of standoff distance will decrease the material removal and depth of hole, and the concentration of abrasives can improve a few of drilling ability. Further, it is founded that longer processing time and smaller standoff distance will achieve higher MASJ drilling efficiency and better quality of hole, with 90 degree jet incidence angle.

Investigation of Chip Formation Characteristics in Orthogonal Cutting of Graphite

Graphite becomes the prevailing electrode material in electron discharge machining (EDM) currently. This article aims to reveal the chip formation characteristics of graphite by orthogonal cutting experiments. The results showed that semicontinuous chip, crushed particle chip, and fractured block chip formation were identified as three major types of graphite chip formation. The transitions of chip formations were highly dependent on the depth of cut. The chips produced in different type of chip formation exhibited different surface fractography. Three types of chip size distribution corresponded well to three types of chip formation. The surface roughness and cutting force increased prominently with the depth of cut increasing. The cutting force response in each type of chip formation can be identified by the fluctuation extent and waveform of cutting force.

Study of Fracture Mechanism of Rock Cutting

This paper presents a review of the authors’ investigation in the cutting processes of 6 diabase and granite. The formation of crushed zone and the propagation of microcracks and cracks 7 under different cutting conditions have been observed in detail by means of a workshop microscope 8 and a polarization microscope. The fracture mechanism is analyzed by measuring the cutting strain 9 field using laser speckle interferometry and comparing the fractography of the cutting chips with 10 those of the samples of tensile test and shear test. The cutting mechanism models of diabase and 11 granite are proposed respectively. 12

Investigation into polishing process of CVD diamond films

A new technique used for polishing chemical vapor deposition (CVD) diamond films has been investigated, by which rough polishing of the CVD diamond films can be achieved efficiently. A CVD diamond film is coated with a thin layer of electrically conductive material in advance, and then electro-discharge machining (EDM) is used to machine the coated surface. As a result, peaks on the surface of the diamond film are removed rapidly. During machining, graphitization of diamond enables the EDM process to continue. The single pulse discharge shows that the material of the coated layer evidently affects removal behavior of the CVD diamond films. Compared with the machining of ordinary metal materials, the process of EDM CVD diamond films possesses a quite different characteristic. The removal mechanism of the CVD diamond films is discussed.

Experimental Study on Cutting Force of High-Speed Micro-Drilling Flexible Printed Circuit Board

Cutting force is one of the most important parameters in the drilling process of FPC (Flexible printed circuit board). It has a directly affect on the micro-drills’ life and the micro-holes quality. It causes the FPC delamination, pulling of the plastic, the burr of exit hole and other processing defects. In this paper, some experimental investigations of cutting force of high speed micro-drilling are carried out to improve the drilling quality of FPC. The results indicate that the drilling parameters(spindle speed, feed speed and drill-bit diameter) have significant influence on micro-drilling thrust force. The thrust force of drill copper foil is larger than the thrust force of drill adhesiver layer and the thrust force of drill PI layer is the smallest. The larger the thrust force is, the bigger the exit burr is.