Experimental Investigations on Cutting Phenomena in Shoulder Cutting of Hardened Die Steel with Small Diameter End Mill: Effects of Left Hand Helical Tool

This study deals with shoulder cutting phenomena in micro-end-milling of hardened die steel. Demand for micro-end-milling for products in the medical, optical, and electronics industry is increasing. However, in machining with a small diameter end mill that has diameter of e.g., 0.5 mm, the rigidity of the tool itself is low; therefore, cutting conditions must be set to low values to achieve stable machining. We revealed that cutting phenomena became unstable because the end cutting edge was damaged early in shoulder cutting. Therefore, we experimentally prepared a left hand helical tool with a right hand cut to perform complete processing by improving the strength of the end cutting edge. Cutting experiments were carried out while measuring cutting force and observing cutting phenomena, end cutting edge, and machined surface via scanning electron microscopy (SEM). We determined the effects of such tools on fundamental phenomena in shoulder cutting with a small diameter end mill. The rake angle of the tool was improved based on experimental analysis of the damage mechanism of the cutting edge in the shoulder cutting. A result of the examination to investigate the influence of the difference in rake angle on chip evacuation showed that the chip discharge direction was affected by the rake angle; when the angle is blunt, the chips were discharged upward, and the chip discharge performance improved.

Investigation of Grinding Fluid for Prevention of Chip Adhesion in Miniature Drilling of Glass Plate Using Electroplated Diamond Tool

In the hole drilling process, produced chip cannot be released from the inside hole which leads to broken glass plate due to the adhered chip on tool. Chip discharge method was announced by many researchers. However, the method using the tool-only with drilling command is rarely seen. In this laboratory, we have developed a tool in order to discharge chip. The developed tool is capable in preventing chip adhesion and producing high quality and efficient hole drilling process. The developed tool has several hundred times longer tool life than a conventional tool. However, the amount of adhered chips on cutting tool increase as the number of hole drilling process increases. The chip adhesion condition is different according to the kind of grinding fluid. Adhesion of chips on tool can be related to the properties of grinding fluid. Thus, in this study, the types of grinding fluid used during the hole drilling process were investigated to determine the state of chip adhesion. Three types of grinding fluid used are Emulsion, Soluble and Solution and all of them include surfactant which is considered to have an effect on prevention of chip adhesion. The main conclusions obtained in this study are as follows. Chip adhesion state was investigated after drilling process and it was found that instead of grinding fluid properties, surfactant also has significant effect on chip adhesion on tool by absorbing the adhered chip from the tool. The results showed that grinding fluid with long-chain surfactant has small amount of chip adhesion whereas grinding fluid with short-chain surfactant has large amount of chip adhesion. Therefore, it can be concluded that grinding fluid with long-chain surfactant is capable in preventing chip adhesion during hole drilling process.

New-Technique Drilling with Modulated Rotation Spindle Machine

In drilling deep holes with small-diameter tools in particular, chip shape is a major problem along with tool rigidity. In this study, we developed a spindle machine that has regularly repeating acceleration and deceleration regions in each drill rotation (called modulated rotation) as a new drilling spidle machine that can improve chip discharge ability. For an analysis of the cutting mechanism based on the basic principles of this device and its drilling characteristics, holes were drilled in CFRP, and Ti alloy (Ti-6A1-4V) materials using a straight shank drill. The relationship between the torque and thrust of cutting resistance force was obtained to show the relationship between cutting chips shape and cutting force. The characteristics of drilling with the developed spindle device were evaluated in comparison with regular drilling methods. It was found that the torque with this device was reduced by about 10% compared with general drilling. Outstanding chip breakup was seen with Titanium alloys in particular, as a result of which chip discharge could be improved.

A Study on the Advanced Surface Characteristic of Yttria (Y2O3) Ceramic by Using Optimal Design of Process

Since a fine ceramic is possessed of creditable physical and chemical material properties: high thermal resistance, chemical inertness and frictional wear resistance, its applications have been increasing in various industrial fields. Yttria(Y2O3) ceramic, which is formed of cubic crystal structure, has been considered as a light-transmitting material for an optical application and suitable buffer layer in the electronic industry. And its other applications have been increasing recently. For the effective applications of Yttria ceramic, it needs to improve a surface characteristic such as the waviness and surface roughness. The lapping process with in-process electrolytic dressing(IED) method has been performed in the surface machining of high hard-brittle material. IED method is able to overcome the surface machining defects caused by worn grains and unstable chip discharge during conventional lapping process. However, the machining control should be carefully conducted and investigated about each material because its material properties are different each other and exceedingly sensitive. Taguchi method, called robust design, is a useful method for engineering productivity elevation. It is able to search a powerful factor, which influences optimal process design, in accordance with considering noise factors reduction. When diverse factors influence a result according to complex actions each other, it needs to search optimal condition of factors. Response surface design has been widely used in various industrial fields. It helps to solve process design problems in accordance with robust design of process condition.

Optimum design of a cutting tool for manufacturing rotary knives

In this article, the design parameters of a cutting tool for manufacturing a rotary knife with multi-cutting angles have been studied. An objective function and constraints are defined, and optimized solutions are found by using two methods: global search and sequential quadratic programming. Hobbing and the concept of tooth undercutting were used to manufacture a rotary knife with multi-cutting angles. The proposed method not only improved the manufacturing efficiency over the traditional method (milling and grinding), but also significantly improved the strength of the rotary knife and the chip discharge ability, as shown by the finite-element analysis of the stress distribution and deformation of two different kinds of rotary knives.