MAXIMIZING INTERLAYER BONDING IN ADDITIVE MANUFACTURING USING AN INTEGRATED OPTIMIZER MODEL

Maximizing interlayer bonding is important to the production of parts using Material Extrusion (MEX) additive manufacturing by reducing the risk of failure by delamination. In MEX additive manufacturing, interlayer bonding is governed by the polymer diffusion characteristics and the highly transient temperature history of printed layers as they become bonded together. Due to continuous cooling from conductive, convective, and radiative heat losses, the time between layers, known as layer time, determines substrate layer temperature and interlayer bonding strength. Therefore, layer time is a process parameter suitable for optimization with the objective of maximizing interlayer bonding. Existing methodologies for optimizing layer times rely upon empirically found layer times for a particular set of bead dimensions and material system. This paper introduces a methodology for optimizing interlayer bonding in a single iteration based on predictions of the transient temperature history for each layer. The integrated optimizer model can optimize the printing process for a defined bonding condition throughout the print by adjusting the layer time using a variable printing speed. The methodology has been demonstrated using a reduced order 1-dimensional heat transfer model and compared to an example constant layer time optimization, with improvements in bonding consistency and strength of bonding as a result when verified against a physics-based process simulation carried out with Additive3D.