The force that moves the development of programmed cutting is neither precision nor accuracy. Because the manual operation by experienced machine tool operators has reached the technical peak before the invention of the computer in the 20th century.
This article discusses about the history of EDM, the electrical discharge wire EDM, and the development of discharge machining.
However, like any other crafts owned by men, the ownership of special skills and the results of processing has not attracted the admiration of business owners and state leaders who pursue high productivity and repeatability.
To overcome this obstacle, people developed CNC machines and applied them to various machine tools, including electrical discharge machining (EDM) equipment, also known as spark machining, spark eroding, burning, die sinking, wire burning or wire erosion. This is a manufacturing process that uses a discharge that usually causes sparks to obtain the target shape.
Electrical Discharge Machines
With NC-controlled EDM machining during the machining process, unwanted work piece materials are removed from the work piece by a series of rapidly recurring current through wire EDM operated by operators’ surveillance.
In the wire EDM assembly, one electrode is called a tool electrode, and the other electrode is called a work piece electrode. The machining process is determined by tools and work pieces that will not actually touch, and avoid many common hearing problems caused by traditional metal processing machinery rather than wire EDM.
Discharge machining was hard to be controlled by manual in the old days but with the NC system, discharge machining can be achieved more easily.
After the numerical control era, due to the development of computers, the 1990s was a mature era of the CNC time, which brought a new processing era to the metal processing industry.
Although most CNC machines are controlled by specific systems, such as Siemens, Mitsubishi, Fanuc, the control system of EDM machines is not dominated by the type of controller supplier, but by the PLC system.
Nowadays, there are many types of CNC wire EDM. In this article, we will discuss a widely used one in the manufacture of household appliances, filter nets, 3C electric consumables, and other smaller sized objects. Discharge machining can be applied to even wider spectrums but here the present article will focus on specific applications of it.
Electrical Discharge Machines In The USSR
During the Soviet period, the development of wire EDM was a success and brought tremendous technological advancement. Wire EDM machines appeared in the late 1960s, and the purpose is to use hardened steel to make tools and molds.
The earliest numerical control (NC) machine was a conversion of a punched-tape vertical milling machine. In the late 1960s, the Soviet Union manufactured the first commercial CNC machine tool in Russia.
It was a wire EDM. During this period, history of EDM was also the history of aerospace, military and defense, and automobile processing were developing in a positive direction.
David H. Dulebohn's team developed a machine for milling and grinding machines by Andrew H. Dulebohn at Andrew Engineering Company in the 1960s. Later in history, a master drawing was produced by a computer numerical control (CNC) plotter to improve accuracy, precision and repeatability.
In the early 1970s, a wire EDM machine using CNC plotters and optical wire follower technology was produced. Since then, Dulebohn later used the same plotter, programmed to control the CNC plotter directly to the EDM machine, and manufactured the first CNC EDM machine in 1976, which provides great processing convenience in the metalworking sector based on the discharge machining.
Automation Added Into EDM
After the wire cutting electrical discharge machining technology controlled by CNC was introduced into commercial applications in the history of EDM, the application has made substantial progress in the last two decades due to the advancement of this technology.
With the introduction of automated mechanisms in the past decade, the feed speed of EDM machines has been significantly increased, and the surface finish can be well controlled by the program.
CNC Wire & Die-sink EDM
In addition to wire-cut EDM, die sinking EDM is also a popular type that can meet many other machining needs. Before the end of the Second World War in the 1940s, when two Russian scientists, B. R. Lazarenko and N. I. Lazarenko, were appointed to study methods to prevent corrosion of tungsten electrical contacts due to sparking effects, the development of sinking molds can be traced back to the early days in the history of EDM development.
They failed to complete this task, but their feats contributed to this technology. Scientists have indeed found that if the electrode is in certain specific environments, the corrosion can be controlled more accurately, which greatly inspired the following experiment.
This new discovery prompted them to invent EDM machines for processing and machining hard materials such as tungsten. The name of Lazarenko machine is called R-C machine, named after the resistance capacitance circuit used to charge the electrodes. This naming is well know in the history of EDM.
At the same time, in the United States, there is an independent situation that is also developing well. There is an American team consisting of Harold Stark, Victor Harding and Jack Beaver. They have successfully developed an EDM machine for removing broken end drills and taps on aluminum castings.
The American team initially used weak electrical-etching tools to make machines. Because they were not very successful at first, they later changed to this method. After that, Stark, Harding, and Beaver machines were able to generate 60 sparks per second, which was a technological breakthrough in the history of EDM at the time.
Today, EDM machines based on their design use vacuum tube circuits. We can generate thousands of sparks per second, greatly increasing the cutting speed, and bringing huge potential and productivity to business owners around the world.