EDM EDM drilling — Corporate manufacture of perfect drill holes

Editor: Steffen Donath

EDM drilling makes it possible to produce the smallest drill holes, independent of material hardness. CFK meet the requirements of their customers for machining of their workpieces each and every day.

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This is not CFK’s first purchase of a Heun machine.
This is not CFK’s first purchase of a Heun machine.
(Source: Heun Funkenerosion)

CFK, a service provider based in Kriftel, Germany, is highly specialised in the fields of wire-cutting, die-sinking, EDM drilling and additive manufacturing. They have been operating in the field of electrical discharge machining (EDM) for more than 30 years. As a result, they dispose over a wide range of EDM drilling technologies and vast experience. Some 70 employees manufacture very small to very big parts — starting with surgical grippers in the micrometre range up to turbine parts and shape plates, which can have a weight of up to 4 t.

The quantities available range from single pieces to serial production of 500,000 parts and more. One particular skill of CFK is EDM drilling. Here, start holes for wire cutting are machined alongside individual drill holes in different drilling angles and single and serial parts with complex hole patterns. Start-hole drilling is required for subsequent processing with wire-cutting machines. For simple workpieces, the start holes are manufactured manually, while for complex parts a program is generated from CAD/CAM data. For challenging cooling holes, parts with a hole pattern or the optimisation of drilled holes, processes and methods are often developed in co-operation with the customer.

A special feature of CFK processing is 5-axis EDM-drilling using 5-axis programming. The five axes are required to position the workpiece, since the electrode is only able to travel vertically.

Aside from individual productions for the mould and die industry as well as automotive industry, CFK also specialises in the fields of aviation and medical technology. “We have gained extensive know-how in programming and techniques, especially for the turbine industry,” tells Christoph Over, managing director of CFK. The requirements very often result in frozen processes, which require a firm working procedure. “In large-part manufacturing, everything must be very accurate,” explains Over. “The raw parts are very expensive. Thus, it is not possible to just try.”

CFK decided to purchase another Heun machine for a variety of reasons — familiarity being one of them.
CFK decided to purchase another Heun machine for a variety of reasons — familiarity being one of them.
(Source: Heun Funkenerosion)

Wide processing spectrum

When the machine parks for EDM drilling had to be expanded, the persons responsible decided on a Heun machine. Heun machines have beeen part and parcel of CFK’s production hall since 1997. At present, CFK has one 3-axis Heun APos 600, one 3-axis Heun A-Pos 1200 and two 5-axis Heun A-Pos 1200s. A third 5-axis machine will shortly be added.

With its Heun machines, CFK is able to machine workpieces up to a size of 2,000 x 1,200 mm, a height of 800 mm and a weight of 8 t. The maximum travel is 1,200 x 600 x 800 mm (X/Y/Z). Electrode diameters from 0.1 to 6 mm can be used. Furthermore, the machines are equipped with a 70-fold electrode changer to enable 24 h run times. “We are one of the few wage-based service providers to provide such machine sizes and such a wide spectrum,” states Over.

Since the purchase of the first Heun machine, a close partnership has evolved between the machine manufacturer and CFK. Back then, the geographical proximity and the fact that Heun was one of the most experienced German producers of CNC machines in the field of EDM drilling were the main reasons for the purchase, according to CFK. “Also, when five-axis technology was introduced, Heun was basically unrivalled,” explains Over. “Heun was one of only two candidates and simply offered better value for money.” Therefore, they remained with the tried-and-tested machine manufacturer.

Technical specifications aside, CFK also appreciates the close communication with Heun.
Technical specifications aside, CFK also appreciates the close communication with Heun.
(Source: Heun Funkenerosion)

Proven machines and systems

CFK has remained very satisfied with the co-operation with Heun to this day. Between the two companies, there is a lively exchange of information. What’s more, detailed and, above all, fast consultation is available thanks to their geographical proximity. Christoph Over knows that “the quality is right and meets their needs”. It is also very important that the employees have already gained experience with the Heun machines and the related control system and thus do not have to be retrained.

Heun’s EDM drilling machines run with Peps, one of the leading CAM systems in the field of wire-cutting, mainly because of its easy operation and the possibility of programming different conics, the company explains. The employees of CFK already know this system. That is why it makes sense to only purchase new machines that run with Peps, like the machines of Heun, CFK notes, explaining the purchase.

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Another advantage is the machining speed of Heun machines. “With hundreds of holes to be drilled, the speed must be fast,” states Over. “Speed and precision are the key factors in EDM drilling.” And not only in this process: Speed also plays a major role in start-hole drilling. “Start-hole drilling is a necessary evil and one generally wants to get it over with as quickly as possible,” says Over.

Co-operation strengthens both sides

To be successful, one needs well-functioning technology as well as close collaboration and active exchange between the machine manufacturer and the operators. There is an active exchange between the employees of CFK and Heun, the company explains. “For example, before the order of the new machine was placed, two of our employees went to Heun to test it on some workpieces in order to see whether the machine would meet our requirements or not,” Over says. If and when this is not the case, the companies co-operate in solving the particular problem. Heun, after all, also grows with the requirements of its customers. Heun listens to the wishes of the operators and thus they are able to develop together.