Machining electrified automotive powertrains

Posted on 27 Jul 2019 and read 595 times
Machining electrified automotive powertrainsOne of the main challenges when producing electrified automotive powertrains is the high-precision machining of the main bore in the stator housing.

Most machining on these housings can be carried out on machines with an HSK A63 spindle configuration, but in most instances the main stator bore usually requires machining with an HSK A100 spindle, due to the high cutting torque required (up to 500Nm) and the tool weight.

However, cost-effective manufacturing with short cycle times is best achieved by complete machining on a single machine with “a small spindle connection”.

These machines are characterised by their high spindle speeds, as well as lower investment and operating costs, which is why Rugby-based Mapal Ltd ( has developed an ultra-light (10kg) fine-boring tool that can be used on machines with smaller spindles.

The company has also optimised the cooling channels and introduced a special back-flushing system that ensures the effective removal of the chips and prevents them from scratching the machined surface.

For the machining of thin-walled battery housings, Mapal has developed its SPM milling cutter.

Thanks to a highly positive cutting-edge geometry and the optimised chip flutes, the cutting force is reduced by up to 15% compared with conventional milling cutters; and if deep pockets are to be machined, Mapal uses special PCD milling cutters.

The cutting edges on these are arranged with both positive and negative axis angles, and in combination with a trochoidal milling strategy, the cutting force is kept very low during machining operations.

Meanwhile, at the heart of an electric refrigerant compressor are two ‘nested’ aluminium spirals, the scroll stator and scroll rotor.

The efficiency of the compressor depends on how precisely these parts are manufactured, and despite thin walls and the depth of the parts, finishing has to be carried out in a single pass.

For this application, Mapal uses its SPM milling cutter with a finishing geometry and a highly positive rake angle; this configuration of the cutter can machine the base, wall and chamfer in a single step.

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