Compensating warpage of 3D printed parts using free-form deformation

3D printing is a common technique for producing complex parts or molds in a small series scale by using ink-jet technology. The size accuracy is of great importance for the use of this technology in the manufacturing sector. However, the chemical solidification reaction of the powder with the binder during the fabrication of parts results in shrinkage. Warpage results whenever shrinkage does not occur uniformly throughout the entire part. Consequently, the size deviation is a result of the layer-wise printing process and the inhomogeneous shrinkage. A possibility to reduce these deviations is a pre-deformation of the part data, contrary to the expected defect. This is implemented by using a free-form deformation (FFD) approach. The FFD deforms the surrounding cuboid of an object in order to adapt the embedded object. Thus, an increased size accuracy is achieved by choosing suitable parameters for the FFD. This paper describes the implementation of the FFD to compensate the significant, frequently appearing defects in the 3D printing process. The relevant defect types and typical values for the deviation are presented. Furthermore, factors of influence are identified and the deviations are described by mathematical functions. These functions are transferred to an application for the FFD. The effect of the FFD is shown for reference parts and suitable compensation parameters are presented. Finally the knowledge-based transfer to related geometries is investigated and the effect of the compensation is discussed. (C) 2015 The Authors. Published by Elsevier B.V.