Ammar Sami Mohammad

Bio: Ammar Sami Mohammad is an academic researcher from International Islamic University Malaysia. The author has contributed to research in topics: Surface roughness & Electrical discharge machining. The author has an hindex of 2, co-authored 2 publications receiving 80 citations.

Experimental Study of Conventional Wire Electrical Discharge Machining for Microfabrication

Abstract: This article discusses the investigation and optimization of the process parameters of conventional wire electrical discharge machining (WEDM) of a copper substrate for microfabrication. The effect of discharge current, pulse-on time, and gap voltage on surface finish were studied. The average surface roughness (R a ) and peak-to-valley height (R t ) were measured with a surface profiler. The surface roughness increased with higher discharge current and gap voltage. With the increase of pulse-on time, the surface roughness decreased. Statistical models were established to predict the surface roughness R a and R t in terms of discharge current, pulse-on time, and gap voltage. Using the optimized parameters, miniaturized spur gears, and plate-shaped hot embossing microtools were fabricated where an average surface roughness of about 1 µ m and dimensional accuracy of 1–2% were achieved.

Effect of Conventional EDM Parameters on the Micromachined Surface Roughness and Fabrication of a Hot Embossing Master Microtool

Abstract: This article discusses the effect of conventional electrical discharge machining (EDM) parameters for generating micrometer and submicrometer leveled surface roughness. Fabrication of submillimeter-sized microstructure to use as a master microtool for replication of polymer microcomponents is also presented. Beryllium copper mold alloy was machined using very low values of three input parameters: discharge current, pulse-on time, and pulse-off time. The input parameters and measured surface roughness were analyzed, and statistical models were developed. The analysis showed that surface roughness increased with the increase of discharge current and pulse-on time. These models were applied to lower values of input parameters to achieve high surface finish. A hot embossing replication master with microchannel structure was produced using the optimized machining parameters with an average surface roughness of 0.60 µm. The replication master was tested with a prototype micro hot embossing machine where it fait...

Micro hot embossing of thermoplastic polymers: a review

Abstract: Micro hot embossing of thermoplastic polymers is a promising process to fabricate high precision and high quality features in micro/nano scale. This technology has experienced more than 40 years development and has been partially applied in industrial production. Three modes of micro hot embossing including plate-to-plate, roll-to-plate and roll-to-roll have been successively developed to meet the increasing demand for large-area patterned polymeric films. This review surveys recent progress of micro hot embossing in terms of polymeric material behavior, embossing process and corresponding apparatus. Besides, challenges and innovations in mold fabrication techniques are comprehensively summarized and industrial applications are systematically cataloged as well. Finally, technical challenges and future trends are presented for micro hot embossing of thermoplastic polymers.

Optimization of Material Removal Rate in Micro-EDM Using Artificial Neural Network and Genetic Algorithms

Abstract: The present work reports on the development of modeling and optimization for micro-electric discharge machining (μ-EDM) process. Artificial neural network (ANN) is used for analyzing the material removal of µ-EDM to establish the parameter optimization model. A feed forward neural network with back propagation algorithm is trained to optimize the number of neurons and number of hidden layers to predict a better material removal rate. A neural network model is developed using MATLAB programming, and the trained neural network is simulated. When experimental and network model results are compared for the performance considered, it is observed that the developed model is within the limits of the agreeable error. Then, genetic algorithms (GAs) have been employed to determine optimum process parameters for any desired output value of machining characteristics. This well-trained neural network model is shown to be effective in estimating the MRR and is improved using optimized machining parameters.

Development of the Cylindrical Wire Electrical Discharge Machining Process

Abstract: Results of applying the wire Electrical Discharge Machining (EDM) process to generate precise cylindrical forms on hard, difficult-to-machine materials are presented. The design of a precise, flexible, and corrosion-resistant underwater rotary spindle is first introduced. A detailed spindle error analysis identifies the major sources of error at different frequency spectrum. The spindle has been added to a conventional two-axis wire EDM machine to enable the generation of free-form cylindrical geometries. The mathematical model for material removal rate of the free-form cylindrical wire EDM process is derived. Experiments were conducted to explore the maximum material removal rate for cylindrical and 2D wire EDM of carbide and brass work-materials. Compared to the conventional 2D wire EDM of the same work-material, higher maximum material removal rates may be achieved in the cylindrical wire EDM, possibly due to better debris flushing condition.

Effect of Wire-EDM Machining Parameters on Surface Roughness and Material Removal Rate of High Strength Armor Steel

Abstract: This work presents the influence of machining parameters on surface roughness (SR) and material removal rate (MRR) of high strength armor steel using wire cut electrical discharge machining (WEDM). Tests have been carried out with six process parameters: pulse-on time, pulse-off time, wire feed, flushing pressure, spark voltage, and wire tension. Taguchi's technique has been employed for experimental investigation. Results show that pulse-on time, pulse-off time, and spark voltage are significant variables to MRR and surface roughness (SR). The confirmation experiments have also been conducted to validate the results obtained by the Taguchi technique.

Technological Advancement in Electrical Discharge Machining with Powder Metallurgy Processed Electrodes: A Review

Abstract: Electrical discharge machining (EDM) is a well-established machining option for processing hard materials with complex geometrical shapes which are extremely difficult-to-machine by conventional machining processes. These hard materials find applications where lower surface cracks, wear resistance, corrosion resistance, etc. are desirable surface properties. In recent years, research has been carried out to determine the possibility of employing electrode as feed stock material in an effort to produce significant surface alloying. These electrodes are generally produced through powder metallurgy (PM) technique in order to achieve necessary combination of operating characteristics. This paper reports state of art related to the usefulness of PM-processed electrodes in imparting desirable surface properties and modification of the machined surface. The final part of the paper outlines the trends for future EDM research using PM-processed electrodes.