Dull Punch Line is Not a Joke – Worn Cutting Edge Causes Higher Iron Losses in Electrical Steel Piercing Sampsa V.A. Laakso 1* , Arijussi Väänänen 2 , Sven Bossuyt 1 and Antero Arkkio 3 1 Department of Mechanical Engineering Aalto University Espoo, 02150, Finland 2 Department of Materials Science and Engineering Aalto University Espoo, 02150, Finland 3 Department of Electrical Engineering and Automation Aalto University Espoo, 02150, Finland Published in: Sampsa V.A. Laakso, Arijussi Väänänen, Sven Bossuyt, Antero Arkkio, Dull punch line is not a joke – Worn cutting edge causes higher iron losses in electrical steel piercing, Robotics and Computer- Integrated Manufacturing, Available online 21 March 2018, ISSN 0736-5845, https://doi.org/10.1016/j.rcim.2018.03.006. Abstract Electrical steel is used for the active parts in electrical machinery that form the magnetic circuits because the material experiences low iron loss, and thus, has superior magnetizing properties. A typical electrical sheet has a thickness of 0.5 mm and is punched into its final shape via a piercing process. Piercing causes large deformations and residual stresses in the narrow zone of the cut surface. The deformations and stresses weaken the magnetic properties of the electrical sheet and result in additional losses, as the iron loss increases after piercing [1]. This paper presents a simulation model of the piercing process to evaluate the deformations and stresses on the cut surface. The model is constructed using the commercial FEM solver Deform. There has been an attempt to simulate the magneto-mechanical state of the punched surfaces, but the piercing process itself was not simulated [2]. The electrical steel sheet investigated in this paper is isotropic electrical silicon steel M400-50A (EN 10106-96). Keywords: Piercing; Electrical Steel; Iron Losses; FEM; Simulation; M400-50A 1. Introduction Non-oriented electrical steels, such as M400-50A, are commonly used in rotating machines. The M400- 50A designation reads as M for magnetising steel with maximum iron losses of 4 W/kg (400), 50 for a thickness of 0.5 mm and A for non-oriented grains. The iron losses in electrical steels can be divided into two main categories: hysteresis losses and dynamic losses. Dynamic losses can be further divided into classical losses and excess losses, which are significantly smaller than dynamic losses [3]. Piercing is a typical process for manufacturing electrical steel sheet parts. It results in good production output, * Sampsa V.A. Laakso, DSc (Tech.): Tel.: +35840 70550 39; E-mail: sampsa.laakso@aalto.fi