Case Study Two heads prove better than one for EDM machining

Editor: Eric Culp

In contrast to high-speed milling, electrical discharge machining (EDM) is nowadays often considered a complementary technology for mould making. ILMA Plastica, an Italian manufacturer of injection tools, is using both techniques to improve its efficiency.

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The EDM unit from ONA has eliminated one processing step and forced the toolmaker to adjust the production flow.
The EDM unit from ONA has eliminated one processing step and forced the toolmaker to adjust the production flow.
(Source: ONA)

Machine tool-related technologies, as tool and mould makers well know, are continually evolving to enable manufacturers to become more and more competitive in the market, according to Antonio Caraffini, president of ILMA Plastica, Oltrona di Gaviratea, Italy, a company specialising in moulds for the automotive industry. He said that fifty years ago, a workshop was equipped with different types of machines: drills, lathes, mills, punchers, copiers, and grinders. But the work performed by some of these units has disappeared or decreased significantly. He noted that at present, the technologies most used at shops are high-speed milling and EDM.

EDM, a long-time mainstay

EDM systems (both wire and die-sinking) have always been one of the fundamental technologies in the manufacture of moulds. In contrast to high-speed milling, in recent years this technique has often been able to find its niche due to notable increases in performance.

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Mario Minichetti, director general of EDM equipment supplier ONA Italia, said concepts and philosophies in the field of erosion, especially die-sinking erosion, have changed completely over the past twenty years. “In the past, the machines worked, in particular, on roughing operations using medium- to large-sized electrodes, discharge control was limited and, therefore, the efficiency and the result were left to the skill of the operator.” He said this process endured until the end of the 1990s, when the arrival of the high-speed milling machine led to a slowdown in the development of new solutions because it was unclear whether HSC technology would completely replace erosion in workshops.

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Such dire predictions proved premature, Minichetti explained. “With time, the high-speed machine was found to be limited in its applications and to have particularly high management costs. Consequently, EDM, boosted by significant developments, began to take on importance again.” He added that innovations have completely transformed this technology, significantly increasing installation performance. Generators can improve control of the process automatically, and graphite electrodes have been running without the supervision of operators who are experts in EDM. Another aspect is the many technological tables on the numerical control, which are a real help to the user.

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