Experimental Study on Micro-Grinding of Ceramics for Micro-Structuring

In this study, micro-grinding was performed to investigate the machining characteristics of alumina and zirconia. The machining of ceramics remains highly challenging owing to their properties, such as high brittleness and wear resistance, which leads to a shorter tool life and high machining costs. Polycrystalline diamond (PCD) was selected as the tool material, as it is suitable for machining hard and brittle materials, and micro-electrical discharge machining (EDM) was used to fabricate PCD micro-tools. When using a resistor-capacitor generator circuit in micro-EDM, the discharging energy is related to the working capacitance, and by controlling the working capacitance, the different edge radii and the surface roughness of the tool can be easily achieved. The feed rate, depth of cut, and rotation speed were set as experimental parameters to investigate the grinding characteristics of the ceramics. During the experiment, the grinding force and roughness of the bottom surface were monitored, and the roughness of the machined surfaces was measured using a three-dimensional surface profiler. A working capacitance of 1000 pF was used to fabricate a tool with an edge radius of 3.5 µm. The lower radius of the tool edge resulted in a decrease of the cutting force by 50% at most and a surface roughness of 19 nm Ra.

Increasing Innovation Capacity of the Methods of Ultrasonic Machining of Ceramics and Composites with a Diamond-Impregnated Tool

In conventional machining, the process of shaping of products from such new materials as alloys with special properties, composite materials and ceramic materials is rather challenged because of low ductility, intense hardness, diversity of physical and mechanical properties of definite components, etc.

Effect of Conductive Coatings on Micro-Electro-Discharge Machinability of Aluminum Nitride Ceramic Using On-Machine-Fabricated Microelectrodes

The objective of this study is to investigate the feasibility of machining micro-holes on the non-conductive Aluminum Nitride (AlN) ceramics using micro-electro-discharge machining (EDM) process by exploiting various coating techniques. Although ceramics possess excellent mechanical properties under compressive load condition and superior thermal properties, machining of microscale features on ceramics remains challenging due to the extreme brittleness associated with ceramics. Due to the involvement of higher cutting force and tool wear issue, conventional machining process appears to be unsuitable for machining ceramics. On the other hand, non-contact and negligible process force associated with EDM process makes it one of the competitive processes for machining of ceramics. A series of experiments were carried out on AlN ceramics using “Assistive Electrode” micro-EDM process with a goal of machining blind micro-holes into the ceramics with the aid of on-machine fabricated copper tungsten tools. It was found that multi-layer coatings of silver and copper with copper tungsten electrode resulted in successful machining with high-aspect-ratio holes during powder mixed micro-EDM of AlN ceramics, while micro-holes with less than one aspect ratio are machined without powder addition to the dielectric. It was also observed that comparatively lower level of discharge energies, i.e., lower value of voltages and capacitances were favorable for successful machining of micro-holes in ceramics, even though it results in significantly higher machining time. Despite of relatively low discharge energy usage in micro-EDM, machined surfaces appear to be very rough. The machined surfaces indicate that melting and evaporation, as well as thermal spalling, are the dominating material removal mechanisms. The machined surfaces contained many thermal cracks and porosity on the surface. The elemental composition analysis confirms the presence of aluminum and nitrogen elements on the machined surface. Finally, by careful selection of machining conditions and assistive electrode, successful machining of micro-holes is possible on the non-conductive ceramic surfaces using the micro-EDM process.

Electro-Discharge Machining of Ceramics: A Review

Conventional machining techniques of ceramics such as milling, drilling, and turning experience high cutting forces as well as extensive tool wear. Nevertheless, non-contact processes such as laser machining and electro-discharge machining (EDM) remain suitable options for machining ceramics materials, which are considered as extremely brittle and hard-to-machine. Considering the importance of ceramic machining, this paper attempts to provide an insight into the state of the art of the EDM process, types of ceramics materials and their applications, as well as the machining techniques involved. This study also presents a concise literature review of experimental and theoretical research studies conducted on the EDM of ceramics. Finally, a section summarizing the major challenges, proposed solutions, and suggestions for future research directions has been included at the end of the paper.

Microelectrical Discharge Machining: A Suitable Process for Machining Ceramics

Today ceramics are used in many industrial applications, for example, in the biomedical field, for high-temperature components or for cutting tools. This is attributed to their excellent mechanical and physical properties, as low density, high strength, and hardness or chemical resistance. However, these specific mechanical properties lead to problems regarding the postprocessing of ceramics. In particular, cutting processes require expensive tools which cause high manufacturing costs to machine ceramics. Consequently, there is a demand for alternative machining processes. Microelectrical discharge machining (micro-EDM) is a thermal abrasion process which is based on electrical discharges between a tool and a workpiece. The advantages of micro-EDM are more and more in focus for ceramic machining. These advantages include the process of being a noncontact technology, an independency of material brittleness and hardness, a low impact on the material, and the achievable microstructures. This paper presents the current state of investigations regarding micro-EDM of ceramics. Beside the process principle of EDM, the used procedures for machining ceramics and insulating ceramics are described. Furthermore several machining examples are presented to demonstrate the possibilities of the micro-EDM process with regard to the machining of ceramics.

A Review on Abrasive Jet Machining Process Parameters

Abrasive jet machining (AJM) also known as abrasive micro-blasting or Pencil blasting is an abrasive blasting machining process that uses abrasives propelled by high velocity gas to erode material from the work piece. It has been applied to rough working such as deburring and rough finishing, machining of ceramics and electronic devices. AJM has become a useful technique for micro machining. It has various distinct advantages over the other non-traditional cutting methods, which are high machining versatility, minimum stresses on the substrate. This paper deals with several experiments that have been conducted by many researchers to assess the influence of abrasive jet machining (AJM) process parameters such as type of abrasive Particle , Abrasive Particle size, Jet pressure Nozzle tip distance. Various experiments were conducted to assess the influence of abrasive jet machine.