The History of CNC EDM: How CNC EDM Evolution Changed Our Industry.

Posted on Nov 12, 2019

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The force that moves the development of programmed cutting is not precision nor accuracy, as a manual operation by experienced machine tool operators has already reached its technical peak in the 20th century when the computer was not invented yet.

The History of CNC EDM: How CNC EDM Evolution Changed Our Industry.

The force that moves the development of programmed cutting is not precision nor accuracy, as a manual operation by experienced machine tool operators has already reached its technical peak in the 20th century when the computer was not invented yet.

However, just like any other crafts owned by men, such ownership of special skills and processing results as a monopolized situation is not that admired by business owners and country leaders who are pursuing great productivity and repeatability. With the intention to conquer such obstacle, numerically controlled machinery was developed and the technology is applied to all kinds of machine tools, including electrical discharge machining (EDM) facilities, which is also known as spark machining, spark eroding, burning, die sinking, wire burning or wire erosion. It is a manufacturing process whereby a targeted shape is obtained by using electrical discharges which normally cause sparks.

Numerical Controlled (NC) EDM

With the NC controlled EDM machining during the process, unwanted workpiece materials are removed from the workpiece by a series of rapidly recurring current through operators’ surveillance. Among the EDM components, one of the electrodes is called the tool-electrode, and the other is called the work piece-electrode. The machining process is determined by the tool and workpiece which would not make actual contact, avoiding much conventional hear issues that were caused by the traditional metalworking machinery.

CNC Wire Cut EDM

After the era of NC, due to the advancement of computers, a full-fledged epoch of CNC time came in the 1990s which brought a new age of machining in the metalworking industry. While most CNC machinery is controlled under specific systems such as Siemens, Mitsubishi, Fanuc, the control system for the EDM machine is not that dominated by that type of controller supplier but rather, more by the PLC system. There are several kinds of CNC EDM processing today and here in the present article, we discuss one type which is largely adopted in the manufacturing of household appliances, filter nets, 3C electric consumables, and other smaller sized objects.

EDM In The USSR

In the days of the USSR, the development of EDM was successful and brought great advancement in technology. Wire-cut type of the EDM machine arose in the late 1960s for the purpose of making tools and dies from hardened steel. The earliest numerical controlled (NC) machine tools were conversions of punched-tape vertical milling machines. The first commercially available NC machinery built as a wire-cut EDM machine was manufactured in the USSR in Russia during the era of the late 1960s in which the processing of aerospace, military, and defense, automotive were growing in an active step.

Machines that could optically follow lines on a master drawing were developed by David H. Dulebohn's group in the 1960s at Andrew Engineering Company for milling and grinding machines. Later in history, master drawings were then produced by computer numerical controlled (CNC) plotters for greater accuracy and precision, and repeatability. A wire-cut EDM machine using the CNC drawing plotter and optic line follower technology was produced in the early 1970s. After that, Dulebohn later used the same plotter CNC programmed to directly control the EDM machine for operation, and the first CNC EDM machine was manufactured in the year 1976, rendering great processing convenience in the metalworking sector.

Automation Added Into EDM

After the introduction into the commercial applications of the wire EDM technology controlled by CNC, the applications have advanced substantially during the recent two decades due to the progress in the technology. Furthermore, with the introduction of automation mechanisms in the current decade, feed rates for the EDM machine have been increased significantly and the surface finish can be eventually well controlled by the program.

CNC Wire & Die-sink EDM

Besides wire cutting EDM, die-sinking EDM is also a popular type in the kind that serves many other processing demands. The development of die-sinking goes back early when two Russian scientists (B. R. Lazarenko and N. I. Lazarenko) were tasked before the end of World War Two in the 1940s to investigate the methods of preventing the erosion of tungsten electrical contacts due to sparking effects. They failed in this task, but their feats contributed to the technology. The scientists did find that the erosion was more precisely controlled if the electrodes were under some specific circumstances and this inspired a lot to the following experiments.

This new finding led them to invent the EDM machine used for processing and machining hard materials such as tungsten. The name of Lazarenko's' machine is called an R-C-type machine, which is named after the resistor-capacitor circuit that is used to charge the electrodes. Meanwhile, in the land of the USA, there was an independent circumstance that also developed well. There was an American team, which was composed of Harold Stark, Victor Harding, and Jack Beaver, who successfully developed an EDM machine for removing broken drills and taps from aluminum castings. The American team initially constructed their machines from feeble electric-etching tools, because they were not very successful at first so that the methodology is redirected later. After that, Stark, Harding, and Beaver's machines were able to produce 60 sparks per second, which is a technological breakthrough at that time.

Today, EDM machines that are based on their design used vacuum tube circuits that we're able to produce thousands of sparks per second, significantly increasing the speed of cutting, rendering great potentiality and productivity for business owners all over the world.

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