Traditional Machining Methods Research Articles

Investigation of electro-discharge micro-machining of titanium super alloy

Being a difficult-to-cut material, titanium alloy suffers poor machinability for most cutting processes, especially the drilling of micro-holes using traditional machining methods. Although electrical discharge machining (EDM) is suitable for machining titanium alloys, selection of machining parameters for higher machining rate and accuracy is a challenging task in machining micro-holes. The present research attempts to optimize micro-EDM process parameters for machining Ti-6Al-4V super alloy. To verify the optimal micro-EDM process parameters settings, metal removal rate (MRR), tool-wear rate (TWR), over cut (OC) and taper were chosen as observed performance criteria. In addition, four independent parameters such as peak current, pulse-on time, flushing pressure, and duty ratio were adopted for evaluation by the Taguchi method. From the ANOVA and S/N ratio graph, the significant process parameters and the optimal combination level of machining parameters were obtained. It is seen that machining performances are affected mostly by the peak current and pulse-on time during micro-electro-discharge machining of titanium alloy. Mathematical models have been developed to establish the relationship between various significant process parameters and micro-EDM performance criteria. In-depth studies have also been made to examine the influence of various process parameters on the white layer and surface topography through SEM micrographs of machined micro-hole.

New methods of internal combustion engine cylinder surface forming

This article comprises a description of methods of internal combustion engine cylinder machining including a description of traditional machining method and a description of some new machining methods – being in use in the motor industry. Special attention has been given to a laser beam treatment method. Results of cylinder surface structure examination after laser-beam treatment with an electron microscopy method and with the use of a scanning microscope have been always presented.

Faster and damage-reduced laser cutting of thick ceramics using a simultaneous prescore approach

Laser machining of structural ceramics is increasingly gaining acceptance as an alternative to traditional machining methods. However, despite the great promise of lasers for a variety of cutting and drilling procedures, premature fractures and prohibitively low cutting speeds are still among the greatest obstacles encountered, particularly when thick cross sections are involved. While many factors contribute to the fractures encountered during laser machining, it is the inevitable and localized increase in temperature and the ensuing thermal stresses that usually cause the damage. As such, the minimization of heat buildup and the resulting thermal stresses often requires the slow and expensive practice of multiple pass or interrupted cutting or drilling. To help avoid the use of multiple-cut methods, while at the same time allowing for faster machining, a unique method of simultaneously scoring and cutting known as prescoring was explored using alumina plates. Using this technique and a design of experiment approach to systematically investigate the effects of various parameters, the use of prescoring was shown to significantly increase cutting rates for relatively thick alumina plates. In addition to improving cutting rates, the method was also shown to be capable of dictating the crack path when fracture could not be avoided.

Studies on NC Machining for Cylindrical Cams

Cylindrical cam mechanisms have many merits, such as compact configuration, low cost, high reliability, better performance of kinematics and dynamics, and they have been widely used in fields of automatization and mechanization. Cylindrical cam mechanisms are the spatial mechanisms. Traditional methods of design and machining for cylindrical cam were complex, and it was difficult to ensure the precision of machining cylindrical cams, so it is impossible to meet the requirement of the development of high-speed automatic equipments. The better method of machining for cylindrical cams is to use the NC milling machine with 3 moving coordinates and 1 revolving coordinate. The key to realize the machining method is to resolve the problem of calculating tool’s paths for NC machining from the motion rule of followers of cam mechanisms. In this paper, the programming principle and technology of NC machining for cylindrical cams were analyzed, the compensation of cutting-tool radius for NC machining was discussed, the method of calculation for motion rule of cam followers and method of programming of NC machining with 4-coordinates were proposed, through which perfect effect have been gained in practice.

Ultrasonic and electric discharge machining to deep and small hole on titanium alloy

Being a difficult-to-cut material, titanium alloy suffers poor machinability for most cutting process, let alone the drilling of small and deep holes using traditional machining methods. Although electric discharge machining (EDM) is suitable to handle titanium alloys, it is not ideal for small and deep holes due to titanium alloys’ low heating conductivity and high tenacity. This paper introduces ultrasonic vibration into micro-EDM and analyzes the effect of ultrasonic vibration on the EDM process. A four-axis EDM machine tool which combines ultrasonic and micro-EDM has been developed. A wire electric discharge grinding (WEDG) unit which can fabricate a micro-electrode on-line, as well as a measuring unit, is set up on this equipment. With a cylindrical tool electrode, made of hard carbide, which has high stiffness, a single-side notch was made along the electrode. Ultrasonic vibration is then introduced into the micro-EDM. Experiments have been carried out and results have shown that holes with a diameter of less than Ø0.2 mm and a depth/diameter ratio of more than 15 can be drilled steadily using this equipment and technology.

バイオマシニングにおける加エメカニズムの解明および加工速度向上に関する試み

Biomachining is a novel machining technology and is different from the traditional physical and chemical machining methods, in which biological energy of bacteria is used as a main energy source for machining process. Previous report has made it clear that the machining speed becomes higher under proper shaking rate and temperature, higher efficient process can be achieved under electric field, and so on. However, the material removal mechanism has not yet been clarified sufficiently.In this report, the material removal mechanism in biomachining was discussed, by comparing the material removal rate for iron and copper. The experimental results indicate that, in the material removal, bacteria acts on the material not only directly, but also indirectly, that is to say, bacteria promotes the change from Fe2+ion to Fe3+ion which has powerful oxidizing effects and makes the material dissolved. Furthermore, the effects of cultured fluid flow on machining characteristic were investigated. As a result, the cultured fluid flow significantly influences the machining rate, and high efficient machining can be achieved by jetting out the cultured fluid from nozzle with high flow rate.

単結晶シリコンの微細穴放電加工に関する研究

Micro machining of brittle materials such as silicon or ceramics is difficult by traditional machining method, since stress generated at machining point causes cracks and fractures. EDM is performed by repetition of micro crater produced by a single discharge and machining force is very small. Therefore, EDM might be used for micro machining of single crystalline silicon. In this paper, EDM characteristics for fine boring of single crystalline silicon were experimentally investigated.Main conclusions obtained in this study are as follows:1) EDM can be carried out for single crystalline silicon whose specific resistance is less than about 10-2Ω·cm.2) The removal rate for single crystalline silicon is 2-10 times as high as that of SUS304.3) In deionized water, the removal rate with copper electrode is 5-10 times higher than that with tungsten electrode.4) The adhesion of silicon to the electrode surface in the normal polarity EDM is remarkable as compared with that in the reversed one, which leads to lower removal rate under the same setting condition.5) The shape of micro hole is better in kerosene type fluid, while the removal rate is 15 times lower than that in deionized water.

Machining of composite materials. Part II: Non-traditional methods

Machining of composite materials is difficult due to the heterogeneity and heat sensitivity of the material and the high abrasiveness of the reinforcing fibres. This results in damage being introduced into the workpiece and very high tool wear. The use of traditional machining methods was reviewed in Part I of this paper. Here new methods are considered: laser, waterjet, electro-discharge, electro-chemical spark, and ultrasonic machining. These various techniques have been applied to organic matrix composites with aramid, glass, graphite fibre reinforcement but also to metal matrix and ceramic matrix composites.

Machining of composite materials. Part I: Traditional methods

Composite materials are more difficult to machine than metals mainly because they are anisotropic, non-homogeneous and their reinforcing fibres are very abrasive. During machining, defects are introduced into the workpiece, and tools wear rapidly. Traditional machining techniques such as drilling or sawing can be used with proper tool design and operating conditions. A review of traditional machining methods applied to organic and metal matrix composites is presented in this article. The use of non-traditional machining methods such as waterjet, laser and ultrasonic machining will be discussed in the second part.

Economic Applications of Pulsed Solid State Lasers

There is a large and growing field of applications where the use of solid state lasers competes on equal terms with more traditional machining methods. This represents a considerable development from the position ten years ago, when lasers were used only for tasks that were either very difficult or impossible by any other method.