REDUCING WARPAGE IN ADDITIVE MANUFACTURING WITH NOVEL TOOLPATH DESIGN

Warpage in Additive Manufacturing (AM) is one of the major unsolved problems, especially with Fused Filament Fabrication (FFF). As layers cool, internal stresses cause nonuniform shrinkage, resulting in undesirable shapes and therefore limited applicability in precision industrial manufacturing. Existing solutions include methods to increase bed adhesion such as brims, rafts, and methods to control the environment such as uniformly heated enclosures, and materials with less shrinkage such as carbon fiber-reinforce polymers to improve stability and resistance to warpage. Recent approaches utilizing pre-deformation involve modifying the initial part geometry to compensate for the warpage rather than preventing it, such that the shrinkage process itself transforms the part into the desired final shape. However, designing such inverse geometries is often imprecise because shrinkage does not occur the same way reversely and it depends strongly on the part shape. Therefore, all of these approaches have pros and cons. In this technical paper, we propose a novel concept to reduce the warpage, demonstrate through FFF printing, and verify the concept by measuring the warpage amount. We provide this novel approach as an additional option as a solution for the users to choose when it comes to a warpage issue. The novel approach we present in this paper, currently filed as a patent application, involves adding extra material into each bead using customizable out-of-plane deposition toolpaths. This method preserves the original part dimensions, allows for compensation in unavoidable shrinkage during solidification, and keeps the total bounding volume constant. We present 3D printing experiments with large shrinkage polymers, Polypropylene and Nylon-11, verifying the applicability of the method with FFF test parts, and demonstrate a warpage reduction by over 40% compared with conventional printing approaches. We intend to extend our method by including various materials, applying them to a larger scale AM and a large range of user-defined input geometries.