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hp tooling 2021 #4

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The journal of hp tooling is an english, global publication on all aspects of high precision tools, accessories and their applications.

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World’s leading trade fair for grinding technology GrindTec 2022 15 - 18 March | Messe Augsburg | Germany | www.grindtec.de materials & tools Comparison of edge zone damage for original LACH EDG procedure and EDM wire cutting; compared to EDM wire cutting the controlled spark gap of the EDG procedure prevents edge zone damages – unnecessary feed depths or complex interventions into the matrix are not required – further finishing is not needed Comparison (as of 1988) of original LACH EDG procedure (left) and EDM wire cutting (right), using the example of a cutting edge (magnifield 1,000 times); clearly visible for EDM is the damage in the edge zone which can be up to 0.02 mm and therefore impacts tool time significantly crystalline material, known as pCD, for the tool manufacturer and in particular for its imminent “success story” in auto mobile, aviation, furniture, wood and plastic processing industries. The patent application in question, with priority of Octo ber 13 th , 1978, was published as European patent on April 21 st , 1982, for a “procedure for machining a polycrystalline synthetic diamond and use of this so-machined diamond.” To place this event in a historical context: up to this discovery, even manufacturers of polycrystalline diamonds (pCD) such as General Electric – and later, at the end of the 1970’s de Beers – were unable to efficiently divide their produced pCD circular blanks into segments. For want of other techniques, the composite pCD material, consisting of a “baked on” diamond layer with an initial thickness from 0.3 to 0.8 mm, would be scored at the desired segment using a thin diamond cut-off wheel and afterwards broken (including the diamond) – at the time this was state-of-the-art technology. During my intensive research regarding this and following reports in connection with the “spark patent”, I found in the professional correspondence of a GE lawyer from November 1983 that GE only then had become aware of using electric sparks as a mean for dividing and form - ing pCD. The following developments at LACH DIAMANT are presented in my previous “poly – poly – or what?” reports [3, 4, 5] ; as well as the, quasi per chance, additionally arising business segment of “diamond tools for wood and plastics” which led to the foundation of LACH-SPEZIAL-Werkzeuge GmbH. “Now Lach lost it completely – he wants to machine wood with diamonds” were typical comments at that time. The further development of NC and CNC machine technology made diamond tools worldwide indispensable for the wood and composite processing industry, the beginning of a triumphal success; but I will cover this in one of the next editions. like winning the lottery The possibilities resulting from the discovery of spark erosion for efficient machining of polycrystalline synthetic cutting materials, pCD and CBN-pCBN, were like a lottery win for the “bundled” LACH DIAMANT and LACH- SpEZIAL businesses. In addition, license and know-how Dia-2100-CNC 1999 Dia-2100-classic 2000 Dia-5085-CNC 2000 28 no. 4, November 2021

World’s leading trade fair for grinding technology GrindTec 2022 15 - 18 March | Messe Augsburg | Germany | www.grindtec.de materials & tools sales contributed their part. The move to the present head office in Donaustrasse in Hanau was conducted in 1984. Despite all euphoria, the question remained how I could control the sparks in order to use best their “erosion potential” for machining, forming, profiling and cutting polycrystalline cutting materials. All this while the competing cutting material carbide had just become “fashionable.” What “spark generating device” was available to us on the market in 1978/79? On one hand, there was the so-called vertical erosion machine and on the other the erosion wire machine (EDM) which was still in a development stage (NC with punched tape). Subsequently, we got to know both procedures, one at the former Matra company (EDM) and the other at Nassovia (vertical erosion). That is why the pCD cutting edges of the worldwide first diamond profile milling cutter for wood and plastic machining were formed on an EDM machine at Matra. This diamond tool with semi-circle overlapping cutting edges, with Ø 13.4 mm each, was delivered to the Resopal H. Römmler GmbH factory in Gross-Umstadt. Now at the very latest, we had to make a decision since the customer announced further orders after the initial successful implementation: wiring or sinking? The time of “free trial work” was over; we had to make an investment. Initially, we decided to use both technologies. ‣ wire: the cutting quality was insofar usable (as of 1979) – however, too time intensive for running it over all the cutting edges of a milling cutter ‣ sinking: the entire electrode width could be utilized for each pCD cutting edge, even as profiled electrode. An advantage – and in the end a significant time factor compared with wire technology In both cases, we can already observe “travelling sparks”, while the sinking procedure is superior to the wiring because the wider electrode is more efficient than the thinner wire when it comes to diamond removal and forming. always room for improvement Initially it was necessary that one worker per vertical eroding machine had to manually advance each tooth of the diamond milling tool to the electrode. This was the beginning of LACH DIAMANT’s machine engineering which automated this process “tooth by tooth.” At first, this helped to avoid an explosive increase in manufacturing costs. But after further brainstorming – there was still room for improvement! This new technology, utilizing sparks to produce polycrystalline diamond tools, was a never-beforerealized symbiosis. “Why not simply bend the rigid electrode – make it circular?” Voilà! What was the result? The circular electrode – “rotation eroding!” And therefore, the birth of the electrical discharge grinding procedure – that is “EDG.” Whether copper or graphite carbon, both are perfect for EDG; however, the graphite electrode comes with the advantage of easier profiling. We chose the name “spark grinding”, a “touchless grinding”, and we added the English term “gentle touch.” “Touchless grinding” triggered an order for ten smaller engraving machines from our “novice” machine engineers in Taiwan, with the plan to equip those later with spark generators – in fact “touchless”, but nevertheless, the less precise, instable axes of these machines ultimately had to be moved. You can surely imagine the result. “This method did not acchieve the desired eroding result.” Thanks to newly employed experienced machine engineers, such as Armin Staub who is still active today, LACH DIAMANT spark grinding machines evolved into longlasting machines with the required stability. Regarding the spark generator and the special software controlling sparks and axes, LACH DIAMANT was able to employ the services of a young, dynamic business under the management of Andreas Weber. Years ahead of time This cooperation is one reason why LACH DIAMANT EDG spark erosion grinding machines were already years ahead of any potential future competitors. Dia-2100-mini 2005 3Dia Saw Grinder 2014 Dia-2200-mini 2016/19 no. 4, November 2021 29

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