A New Structural Bonding Process for Ferromagnetic Sheet Stacking used in Electric Motors (Rotors, Stators…)  Christophe Casteras*, Bruno Bonduelle** and Frederic Martin***  Abstract  A new structural bonding process has been developed for the assembly of the thin iron sheet stacking  used in electrical motors. This process, based on screen printing technology, improves the stack  cohesion and allows very precise geometrical dimension machining. A stator has been assembled based  on such a structurally bonded stack, and it has been submitted to a complete qualification test sequence  similar to an existing space-qualified stator with a potted stack. Process development, test results, and  comparisons are presented hereafter.  Introduction  A new onset of brushless DC motors for space was developed at SOTEREM for a satellite platform  application. This electrical motor is a large and powerful one, whose performance at high rotation speeds  is disturbed by eddy current. To lower the eddy current, ferromagnetic thin sheet stacking must be used for the stator. The potting employed to maintain this stack was already qualified but was deemed difficult  to produce and has some industrial constraints for large diameter stators.  So, in parallel, a structural technique of bonded assembly was developed by CLIX Industries under CNES  funding, to solve the stator ferromagnetic sheet stacking issue. The objectives were to increase cohesion  and rigidity, to reduce the structural mass, to increa se electromagnetic performance, to improve the  workability of stacking without delamination, and finally to obtain better manufacturing precision. The  difficulty with the structural bonding tech nique is to obtain very thin uniform ad hesive joints (of about few  microns), which increases the iron/insulator ratio and generates an insulating layer at any point to limit iron losses.   The first part of the article presents a new process that relies on a technique of adhesive serigraphy  adapted to adhesive rheology prope rties. Screen printing technology is used for assembling thin  ferromagnetic sheet stacks with structural bonding. This technology makes the depositing of very thin and regular adhesive films on to the elementary parts of a stator stack possible. All kinds of resins can be  applied including structural adhesives with a wide range of viscosities and tacks.  In addition, this structural bonding technology makes stacks machinable. An original method of wire  electro-erosion machining was developed to cut out the stacks (insulating layer & conductor sheet) after  gluing. This technique makes it possible to avoid tolerance issues of elementary components and to increase precision of the final stator geometry.  The second part of the article pres ents the test results of the evaluation  campaign towards space and  launch environment that has been performed on the motor equipped with the previous potted stator. A  comparison with a similar space-qualified stator, based on a varnished structurally bonded stack, is also  given. * CNES, Toulouse, France  ** SOTEREM, Castanet Tolosan, France  *** CLIX Industries, Toulouse, France  Proceedings of the 39th Aerospace Mechanisms Symposium, NASA Marshall Space Flight Center, May 7-9, 2008  61