A Wear Investigation of Repeatedly Used Wire in Wire Cut Electrical Discharge Machine
Wire electro-discharge machining (WEDM) is a fully extended and competitive machining process widely used for hard and difficult to machine materials. In the present research, experimental investigation have been conducted to find out the wire wear rate at different machining parameter Such as peak current, pulse on time, pulse off time, based on full factorial design of experiment. Molybdenum wire of 0.18 mm and EN-8 material were used as tool and work piece material for the experiment, ANOVA analysis were done to find out the effect of peak current, pulse on time, pulse off time on wire wear and found that the increasing in peak current slowly increase the wire wear but increasing in pulse on time increase the wire wear rapidly and pulse off time not much affects the wire wear. Keywords— WEDM, WWR, ANOVA, Full factorial,
On-line prevention of wire breakage in wire electro-discharge machining
Wire electro-discharge machining (WEDM) is a fully extended and competitive machining process widely used to produce dies and moulds. However, the risk of wire breakage affects adversely the full potential of WEDM since the overall process efficiency is considerably reduced. The present paper discusses the results of the analyses of an exhaustive experimental database that reproduces unexpected disturbances that may appear during normal operation. The results of the analyses reveal new symptoms that allow one to predict wire breakage. These symptoms are especially related to the occurrence of an increase in discharge energy, peak current, as well as increases and/or decreases in ignition delay time. The differences observed in the symptoms related to workpiece thickness are also studied. Another contribution of this paper is the analyses of the distribution of the anticipation time for different validation tests. Based on the results of the analyses, this paper contributes to improve the process performance through a novel wire breakage monitoring and diagnosing system. It consists of two well differentiated parts: the virtual instrumentation system (VIS) that measures relevant magnitudes, and the diagnostic system (DS) that detects low quality cutting regimes and predicts wire breakage. It has been successfully validated through a considerable number of experimental tests performed on an industrial WEDM machine for different workpiece thickness. The efficiency of the supervision system has been quantified through an efficiency rate defined in this paper.
Arc flash hazard assessment in the mining industry
When it comes to electrical safety in the workplace, arc flash has become the most prominent topic over the past decade. The Occupational Safety and Health Administration (OSHA, including state chapters) is the only government body that recognizes NFPA-70E, Standard for Electrical Safety in the Workplace. However, OSHA does not have jurisdiction in mining operations. Electrical safety for the metal and nonmetal surface mining industry is covered by the Code of Federal Regulations (CFR) Title 30, Part 56, Subpart K (Electricity). The Mine Safety and Health Administration (MSHA) is responsible for enforcing electrical safety in mining operations. CFR Title 30 does not reference personal protective equipment (PPE) to protect electrical workers against arc flash hazards. This paper provides maintenance and safety personnel in surface Metal/Nonmetal mining operations with a step by step guide to implementing an electrical safety program that meets the requirements of MSHA, CFR Title 30 and NFPA-70E.