Structural FEA of Asymmetrically Loaded Washing Machine Drums

The walls of a washing machine drum are perforated (punctured with holes) creating a tessellated array of frustums which allow water in and out of the drum (in when washing, out when spinning). The shape, proximity, arrangement, orientation and spatial density of the frustums affect the torsional and bending stiffness of the drum. The frustum design features listed in a European patent conferred (according to the patent holders) an improved drum bending stiffness (of +25%), thereby distinguishing it from the prior art. A competitor, believing their existing patent had been infringed, contested the legality of this patent. 

To resolve the dispute Double Precision Consultants were instructed by lawyers from a multinational law firm (and a member of the UK’s Magic Circle of leading law firms) to conduct elastic finite element simulations of the various drum designs. 

When the drum designs were ranked (according to stored strain energy density), the supposed improvements in bending stiffness were, in fact, not realised. An equivalent experimental programme would have been significantly more expensive, and taken substantially longer, than the corresponding finite element simulations.