A system for selectively encapsulating porogens inside the layers during additive manufacturing: From conceptual design to the first prototype

Additive manufacturing (AM) has greatly expanded the range of part fabrication to encompass both geometrical complexity and material variation. However, challenges still remain with respect to the implementation of AM technologies. One such issue is related to the de-powdering step required for the removal of support powder inside internal channels and voids during powder-bed AM approaches. This study proposes a novel design and methodology for selectively encapsulating the sacrificial paraffin particles inside the powder layers during the binder jet AM process. The paraffin particles will be generated by punching through the sheet of material which includes a mesh structure carrying a thin layer of wax. Several experiments were designed to evaluate the performance of the proposed system, particularly the effect of input parameters on the size, shape and number of porogen particles as well as their distribution on the substrate. The obtained results revealed the direct influence of mesh structural properties on the porogen particle morphology. Moreover, applying the lower voltage (8 V) and needle diameter (0.28 mu m) to separate the porogen improved the repeatability of the range of data (52 +/- 3%-80 +/- 12%), distributing the particles in the area less than 1 mm distance from the center of needle. Then, four categories of the samples were designed for the AM process, 3 samples including porogen of different sizes, and one control sample. The porosity of the specimens measured after sintering process did not show any significant variations among the samples (35.5 +/- 1%-37.7 5%), due to the limited number of encapsulated porogen. The average diameter of the pores, after removing porogen during the heat treatment phase, illustrates the close similarity to the porogen particles size. (C) 2017 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.