Investigation of Digital Computer Aided Design Assembly and Tesselation Effects on Digital ABS Part Quality in Polyjet 3D Additive Manufacturing

Current PolyJet technology systems for additive manufacturing (AM) have an ability to create geometric design features, multi and complex material morphologies with built layer thicknesses in the order of tens of microns. This paper investigates digital design approximations involving non-coplanar and planar sub-assembled computer-aided design (CAD) models on Digital ABS (Acrylonitrile Butadiene Styrene) part quality in a PolyJet-3D process. A test part configuration involving non-coplanar and planar inclusions is employed, and differences in part quality when AM printed with a single material (Digital ABS) modeled as a single part or assembly are analyzed. Digital approximation errors due to non-coplanar inclusions resulted in imperfections in print/material quality and defects at sub-assembly interfaces even when printed with single Digital ABS material. Findings indicate that non-coplanar assembled digital designs lead to imperfections in printed material quality and defects due to tessellation errors. Presence of such imperfections was dependent upon tolerances used in a polygonal approximation of curved geometries. Digital design approximations not only impact the final part quality but also its mechanical behavior. AM parts formed with Digital ABS using a Stratasys PolyJet system were found to show brittle material characteristics when test coupons were printed using digital designs from sub-assemblies of non-coplanar geometrical features. In contrast, PolyJet printed test coupons from digital designs of non-assembled and assembled planar configurations showed ductile material characteristics.