Mohamed Konneh

Cooling Effect on Electrode and Process Parameters in EDM

In electrical discharge machining (EDM), material is removed by a series of electrical sparks that develops a temperature in the range 8, 000°C–12, 000°C between the electrode and the workpiece. Due to the high temperature of the sparks, the workpiece is melted and vaporized. At the same time, the electrode material is also eroded by melting and vaporization. This erosion of the electrode is termed as electrode wear (EW). The EW process is similar to the material removal mechanism as the electrode and the workpiece are considered as a set of electrodes in EDM. Due to EW, electrodes lose their dimensions resulting in inaccuracy of the cavity formed by EDM. This paper reports on the study of the effect of electrode cooling during the EDM of titanium alloy (Ti-6Al-4 V). Investigation on the effect of electrode cooling on electrode wear was carried out. Current, pulse on-time, pause off-time, and gap voltage were considered as the machining parameters while EW is the response. Analysis of the influence of electrode cooling on the response has been carried out, and it was possible to reduce EW by 27% using this method.

Microwave hybrid heating of materials using susceptors -A brief review

This article discusses the fundamentals and benefits of microwave hybrid heating. High dielectric loss materials can be processed using direct microwave heating, whereas low dielectric loss materials can only be process using microwave through microwave hybrid heating. It was shown that it is possible to virtually process any type of materials via microwave hybrid heating. Microwave hybrid heating offers faster heating rate than direct microwave heating. It reduces the problem of thermal runaway experience in direct microwave heating of high dielectric loss materials. The two basic types of microwave hybrid heating techniques were discussed with emphasis on the use of susceptor. Microwave hybrid heating using susceptor offers the advantage of using single energy source.

Influence of Electrode Cooling on Recast Layers and Micro Crack in EDM of Titanium

Electrical discharge machining (EDM) process is a manufacturing method for shaping hard metals and formation of deep and complex shaped hole by spark erosion in electrical conductive materials such as metals, metallic alloys, ceramics etc. EDM process is achieved by a series of recurring electrical discharges between the electrode and workpiece in the presence of dielectric fluid. EDM unique feature of using thermal energy to machine conductive materials irrespective of material hardness has been its major advantage in the manufacture of aerospace, surgical, mould, die, automotive and as well as sport components. The effectiveness of EDM process depends among other factors on the thermal properties of the electrode material. The objective of this study is to study the influence of electrode cooling on recast layers and micro crack in EDM of titanium. The machining parameters investigated in the present study are current intensity (I), pulse on-time (Ton), pulse off-time (Toff) and gap voltage (V), which are of great interest for EDM researchers. The copper electrode is used to EDM titanium workpiece at room temperature and at sub-zero temperature using liquid nitrogen. The influence of cooling of copper electrode on recast layers and micro crack on titanium were investigated using scanning electron microscope (SEM) and has been reported in this study.

Reducing Electrode Wear Using Cryogenic Cooling during Electrical Discharge Machining

In electrical discharge machining (EDM), material is removed by a series of electrical discharge between the electrode (tool) and the workpiece that develops a temperature of about 8,0000C to 12,0000C. Due to high temperature of the sparks, work material is melted and vapourized, at the same time the electrode material is also eroded by melting and vapourization. Electrodes wear (EW) process is quite similar to the material removal mechanism as the electrode and the workpiece are considered as a set of electrode in EDM. In the present study effort has been made to reduce EW by cooling, using liquid nitrogen during the EDM of titanium alloy. Investigation on the effect of cooling on electrode wear (EW), material removal rate (MRR) and surface roughness (Ra) of the workpiece was carried out. Current (I), pulse on-time (ton), pause off-time (toff) and voltage (v) were considered as the machining parameters. Design of experiment (DOE) was used to design the experimental works. Cooling of electrode by this technique reduced the melting and vapourization of electrode material and enhances electrode life. It was possible to reduce EW up to 27% by applying this technique while MRR and Ra were improved by 18% and 8% respectively.

Milling damage on Carbon Fibre Reinforced Polymer using TiAlN coated End mills

This paper reports on the damage caused by milling Carbon Fibre Reinforced Composite (CFRP) with 2-flute 4 mm-diameter solid carbide end mills, coated with titanium aluminium nitride. The machining parameters considered in work are, rotation speed, feed rate and depth of cut. Experiments were designed based on Box-Behnken design and the experiments conducted on a Mikrotool DT-110 CNC micro machine. A laser tachometer was used to ascertain a rotational speed for conducting any machining trial. Optical microscopy examination reveals minimum delamination value of 4.05 mm at the spindle speed of 25,000 rpm, depth of cut of 50μm and feed rate of 3 mm/min and the maximum delamination value of 5.04 mm at the spindle speed of 35000 rpm, depth of cut of 150μm and feed rate of 9 mm/min A mathematical model relating the milling parameters and delamination has been established.

Surface Roughness Study of Milled Carbon Fiber Reinforced Polymer (CFRP) Composite Using 4 mm 2-Flute Titanium Aluminum Nitride (TiAlN) Coated Carbide End Mills

As the goal for aircraft weight reduction and low fuel consumption becomes a dire concern in aerospace industries, there is driving desire for the increasing use of advanced exotic materials such as composites, titanium and Inconels in the aerospace industry because of their high strength to weight ratio. Nevertheless the inherent anisotropy, inhomogeneous properties of CFRP and low bonding strength within the laminates make machining of these composite materials results in several undesirable effects such as delamination, micro-cracking, burr, fiber pull out and breakage. This paper discusses an experimental investigation into the influence of machining parameters on surface roughness when milling CFRP using 4 mm-diameter 2-fluted carbide end-mill coated with Titanium Aluminium Nitride (TiAlN). Relationship between the machining variables and the output variables is established and a mathematical model is predicted for the surface roughness produced during the milling process for the machining conditions investigated.

Surface Roughness Prediction in High Speed Flat End Milling of Ti-6Al- 4V and Optimization by Desirability Function of RSM

High Speed Machining is applicable for producing parts that require little or no grinding / polishing operations within the required machining tolerances. For achieving required level of quality, selection of cutting tools and parameters in high speed machining is very important. In this study, small diameter flat end milling tool was used to achieve high rpm to facilitate the application of low values of feed and depth of cut to achieve better surface roughness. Machining was performed on a Vertical Machining Centre (VMC) with a high speed milling attachment (HES 510), using cutting speed, depth of cut, and feed as machining variables. Statistical prediction model of average surface roughness was developed using three-level full factorial design of experiments. It was observed that depth of cut is the most dominating factor followed by cutting speed and feed. The developed model was used for optimization by desirability function approach to obtain minimum Ra. Maximum desirability of 95.63% was obtained.

Influence of Electrode Cooling on Material Migration among the Electrodes during EDM of Titanium Alloy

Electrical discharge machining (EDM) is widely used in the machining of electrically conductive hard metals for the production of dies and moulds. This paper describes an investigation of the effect of electrode cooling on the amount of elements migration from the electrode to the workpiece surface and from the workpiece to the electrode surface. In the present study EDM has been performed with electrodes cooled by liquid nitrogen as well as with electrodes without cooling. Current, pulse-on time, pulse-off time and voltage were taken as the variables during conducting the experiments. The analysis on material migration during EDM was carried out by SEM and EDX. It was observed that EDM with liquid nitrogen reduces material migration and minimizes the surface contamination of both the electrodes.

Virtual Simulation and Remote Desktop Interface for CNC Milling Operation

Advanced development of computer network through Internet brings the technology to Manufacturing. Increasing the demand for effectively use of the production facility requires the tools for sharing the manufacturing facility by remote operation of the machining process. This paper introduces the methodology of machining technology for direct remote operation of networked milling machine. The tools including virtual simulation using CAD model, remote desktop protocol and Setup Free Attachment for remote operation of milling process are proposed. Accessing and monitoring of machining operation is performed by remote desktop interface and 3D virtual simulations. Capability of remote operation is supported by an auto setup attachment with a reconfigurable pin type setup free technology installed on the table of CNC milling machine to perform unattended machining process. The system is designed using a computer server and connected to a PC based controlled CNC machine for real time monitoring. A client will access the server through internet communication and virtually simulate the machine activity. The result has been presented that combination between real time virtual simulation and remote desktop tool is enabling to operate all machine tool functions and as well as workpiece setup.

Effect of pickling and mechanical surface treatment methods on adhesion strength of Ti oxide layer formed on Titanium alloy substrate

Titanium alloys are commonly used in biomedical application in hard tissues replacement especially for knee and hip implants but facing huge wear debris due to continuous cyclic contact within the joints of the implants. Diamond coating is a potential solution for improving the tribological and wear properties of the implants made from this alloy. Diamond is known for having high wear resistance property and chemical vapour deposition (CVD) is one of the most promising methods for diamond coating. However, the major concern for CVD process is the poor adhesion of the diamond to the substrate material due to the large mismatch of coefficient of thermal expansion (CTE) properties between the two. A suitable interlayer material can be introduced to reduce the gap of CTE differences by oxidation process. In this study, the effect of pickling temperature and mechanical surface treatment methods on the adhesion strength of Ti oxide interlayer prior to diamond coating were investigated. Besides, the thickness of oxide layer and surface morphology were also evaluated. Experiments were carried out on Ti6Al4V substrate by varying the surface treatment pickling temperature from 25°C to 50°C. In mechanical surface treatment, all samples were ground using #220 to #1200 grits and followed with polishing using alumina paste. After the surface treatment process, all the substrates underwent thermal oxidation for 25 hours at 900°C. The results showed that the adhesion strength of oxide layer increases with the increasing of pickling temperature. Mechanical surface pretreatment provides better adhesion of oxide layer than chemical pretreatment (pickling process). However, the adhesion strength decreases with the increases of oxide layer thickness.