GKN Powder Metallurgy (www.gkn.com) and Porsche Engineering (www.porscheengineering.com) are ‘growing’ the metal AM process to make it suitable for new e-drive powertrain applications.

A new powder material — 20MnCr5 — has characteristics that are key for parts used by the automotive industry.

Porsche Engineering has been investigating how to use this material for components of its e-drive powertrains. Using the technique of structural optimisation in combination with GKN’s AM and 20MnCr5, a unique design of a differential — including the ring gear — has been developed, leading to a more efficient transmission.

GKN developed 20MnCr5 as an optimal candidate for laser powder-bed fusion. It is a medium-strength steel that can be case-hardened.

To validate the potential of the powder and methodology, GKN and Porsche used 20MnCr5 on a conventional front transverse transmission.

The differential housing is normally produced by casting. Finite-element analysis showed a very homogeneous stress level and allowed the wall thickness to be reduced.

Based on the original load requirements, the calculation shows that the following was achieved: 13% weight reduction (about 1kg); 43% decrease of tooth stiffness variations in the radial direction; 69% decrease of tooth stiffness variations in the tangential direction; and 8% inertia reduction.