High-End-Technologie in
engine production

Angular heads by ROMAI for Compensating Bores in Crankcases

ROMAI-Winkelköpfe bei BMW

Compensating bores or pulsation holes, as they are called at BMW in Steyr, are bores running laterally in the crankshaft bearings of 6-cylinder gasoline engines. In order to implement these, additional front-end holes would have to be drilled, which afterwards would have to be closed with screw plugs. A specially developed angular head by ROMAI, adapted to the tight space available within the crankcase, as well as to the high cutting forces, and the limitations of the automatical tool changer (atc), makes this effort redundant.

The milling of the so-called pulsation holes on the crankcase is seen as one of the most challenging machining steps when manufacturing 6-cylinder gasoline engines. Pulsation holes are pressure compensation holes, which run laterally within the crankshaft bearings. In order to manufacture these in the conventional way, front-end holes have to be drilled on the crankcases from both sides across the whole chain casing. As a tool, a 3-stage spiral drill would be used. Apart from the effort of three additional bores, the front-end holes would have to be closed again in a downstream bolting station.