Drilling EDM & Discharging Process

Posted on Jan 13, 2019

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Drilling EDM & Discharging Process

Conventional drilling machines or tools often cause many chip and overheat issues during the drilling process, and these issues have always been the key to hindering the precision and quality of output.

About Drilling EDM

The process of traditional drilling machines has issues of chip and overheats, reducing the output accuracy and quality. Starting around 1040s, industry professionals began to study some methods to overcome these obstacles, and EDM is one of the solutions.

Electrical discharge machining (EDM) is also known as spark machining, spark eroding, burning, die sinking, wire burning, or wire erosion. These are named by workers in different countries or different industrial fields. EDM is a machining method that uses sparks to produce metal work pieces of different shapes, so it is also called sparking machining in the Chinese market.

 

Working and classfication

During EDM machining, excess metal material is removed from the work piece through a series of rapidly recurring current. One of the critical electrodes is called the tool electrode. Nowadays, there are many types of EDM. Here we will discuss one of the types widely used in metal processing and manufacturing. It can be used to process household appliances, filters, 3C electrical consumables, and other smaller size work pieces.

 

Small Hole drilling EDM

The small hole drilling EDM is used to make a through hole in a work piece, and then the wire for wire-cut EDM operation passes through the through hole. A separate EDM head designed for small hole drilling will be installed on the wire cutter and allow large hardened plates to corrode finished parts from it as needed. Small hole drilling EDM is used to drill rows of holes in the leading and trailing edges of the turbine blades of jet engines. Airflow through these small holes by drilling EDM will allow the engine to withstand higher temperatures.

 

Historical development of EDM technology

Wire-cut electric discharge machine tools emerged in the late 1960s, and their purpose was to manufacture tools and molds from hardened steel. The earliest NC machine tools were derived from the transformation of perforated vertical milling machines. In the late 1960s, the Soviet Union manufactured the first commercial CNC machine tool in Russia, which is wire EDM machine tool. During this period, the processing of aerospace, military and national defense, and automobiles is moving in a positive direction.

 

Demands stimulates progress

In the 1960s David H. Dulebohn's group developed machine tools for milling and grinding machines at Andrew Engineering Company. Then, master drawing is made by a computer numerical control (CNC) plotter to reach higher accuracy and repeatability. In the early 1970s, a wire-cut EDM machine equipped with CNC drawing plotter and optical line follower technology was produced.

Based on this development, Dulebohn then used the plotter CNC to program to directly control the operation of the EDM machine, and produced the first CNC EDM machine in 1976. The capability and application of commercial EDM wire cutting have made great progress in recent decades. In addition, the feeding speed of the EDM machine has been greatly improved, and the finish of the surface finish can be well controlled.

 

Other kind of EDM machining

In addition to wire cutting and drilling EDM, die sinking EDM is also widely used in the industry to process special work pieces. The history of die sinking EDM machine can be traced back to the end of the Second World War (WWII) in 1943. Two Russian scientists (named BR Lazarenko and NI Lazarenko) were instructed to study methods to prevent erosion of tungsten electrical contacts due to sparking effects. They discovered physical principles in the laboratory, which later changed the entire industry.

Their efforts contributed to this technology. They found that when the electrode is in a specific condition, the erosion can be controlled more accurately, which greatly inspired subsequent scientific and industrial experiments. This knowledge prompted them to invent an EDM machine tool for machining hard materials such as tungsten. Lazarenko’s machine is called as an R-C-type machine, which means resistor-capacitor.

 

Today’s applications

EDM is a very common metal cutting technology today, used to process hard and complex materials. It is widely used in the mold and tool manufacturing. Now, it is also applied to make prototypes and parts, especially in the aerospace, automotive and electronics fields.

Read More: Drilling machining process

 

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