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As a system supplier for stamping and forming , welding and assembly technology , family-owned Otto Bihler Maschinenfabrik ( Bihler ) has over 70 years of experience “ Made in Germany ”. Using a new process , Bihler is now making the removal of isolation from hairpins more reliable and efficient . Its solution centres around the innovative sensor unit , which continuously measures the enamelled copper wire . The downstream isolation removal station then uses this data to precision-strip the isolation from each hairpin individually , with “ minimum loss of cross-section and in a way that ensures pure metal surfaces ,” according to the company .
The manufacture of hairpins made from enamelled copper wire has long been one of Bihler ’ s core fields of expertise . Hairpins are firmly established components in electric motors and demand for them has grown greatly in recent times due to the increasing popularity of e-mobility . That is why Bihler recently developed its BM-HP servo system , a fully automatic , end-to-end system that can manufacture up to 120 hairpins per minute and allows “ on-the-fly ” variant changes . “ The system guarantees absolute dimensional accuracy at the level of head shape , length and parallelism of the individual pin legs and , most importantly , guarantees the reproducibility of the 3D head geometry of each pin ,” confirmed Bihler .
Above : The new process for removing the isolation from hairpins is integrated in the BM-HP servo system , which can manufacture up to 120 hairpins per minute .
Intelligent removal of isolation from hairpins
Material removal
At the same time , Bihler is concentrating on further developing its hairpin manufacturing process . One particular challenge lies in removing the isolation from the ends of the pins .
“ The important thing is to produce a pure metal surface at the ends of the pin legs that is completely free from any enamel residue . At the same time , the cross-section of the copper wire must only be marginally reduced by the stripping-off of the enamel coating ,” explained Martin Lehmann , Bihler Key Account Manager , E-Mobility . This is particularly important from a safety perspective because inadequate leg crosssections would result in unwanted heating at the connecting points . However , it is equally vital that the coating is stripped away cleanly and without residue because the pin ends must be completely free from contamination if they are to be welded at the stator plate following assembly .
The task of stripping the isolation from the ends of the hairpins is made more difficult by the fact that many different enamel and coating variants may be applied to the copper body . The tolerances of the copper wire must also be considered . The centre of the copper wire is often slightly offset in the enamel coating , which is itself not of a uniform thickness . To compensate for these tolerances and reliably obtain a pure metal surface , a corresponding amount of material must be removed , unfortunately with the exact unwanted effect of making the cross-section too small and wasting a lot of valuable material .
This is the environment in which Bihler developed the isolation removal station . It shuns the conventional laser beambased approach and instead works purely mechanically . The enamel used to coat the surface that is to be stripped is unimportant . “ We can shave off any coating ,” stressed Lehmann . “ This allows us to produce an extremely high-quality surface while also working with precision .”
Hairpins made from enamelled copper wire are an integral part of all electric motors .
88 | ismr . net | ISMR April 2024