The advantages of wet-milling electrodes

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Higher dimensional accuracy

For this, graphite electrodes were specially manufactured with Seagull ball milling tools (B-2-20-60) on two Mikron Mill S400 machines from GF Machining Solutions. Cooling is performed directly at the milling point with compressed air on the one hand and emulsion on the other. To check the run and the diameter of the milling tool, it was measured before and after with the 1210 laser measuring device from z-Mike. Contour and surface were optically checked with C-View from Cimtrode with 1,000-fold magnification.

“The results speak clearly for wet machining: After 290 minutes of milling time, the tools used with cooling lubricant showed 30 percent less wear than those from dry machining. After 490 minutes, the result was even more clearly in favour of wet machining: 40 percent less wear,” said an impressed Daniel Gruber, Managing Director of Cimtrode. The wear with cooling lubricant was, at most, 0.0052 mm; without it, it was 0.0087 mm.

Here, wet machining was not only responsible for longer tool life but also the significant increase in the dimensional accuracy of the electrodes. After 490 minutes, the dimensional accuracy of the wet-processed electrode was still within the tolerance range of 0.005 mm. In dry machining, there were significant dimensional deviations.

Positive effects on quality measurements and accuracy

“Excellent time results for the milling tools and high levels of sustainability in the electrodes were one side of the coin, now the erosion results also had to be right,” says Arndt Fielen. For this, the erosion time, the surface roughness on the finished component and the erosion of the electrodes were compared in several conducted tests. In the test set-up, a roughing electrode and a finishing electrode were used. The erosion was between 3 and 6 µm, the roughness of the surface at the component between Ra 0.82 to 0.87. All electrodes were used for around 40 minutes.

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In contrast to dry milling, using lubricant enables tool and mould manufacturers to machine copper, graphite and steel on the same machine and ensures greater cleanliness. Tool lives are extended, tool costs reduced and the dimensional stability is increased.

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