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Additive manufacturing technologies enable the production of parts by successively adding layers. In powder-based technologies, each powder layer is selectively solidified following the respective cross-section of the parts either by the application of high-energy radiation or by the selective deposition of binder. By repeating the steps of layer deposition and selective solidification, parts are fabricated. The layer-wise build-up and the ambient conditions lead to warpage of the parts due to the temporarily and locally uneven distribution of shrinkage throughout the part. This leads to deviations in shape and dimension. The development of these technologies fosters a change from prototyping to manufacturing applications. As a consequence, higher standards regarding the shape and dimensional accuracy are required. Therefore, new strategies to minimize the resulting deformations are necessary to reduce rejects and widen the range of applications of the described technologies. In this paper, an empirical, a knowledge-based and a simulative approach for warpage compensation are introduced. They are all based on the pre-deformation of the digital 3D part geometry inverse to the expected deformation during manufacturing. The aim of the research is the development of a comprehensive method that enables users to improve their part-quality by supporting the pre-deformation process. Contrary to existing work, this method should not be process-specific but cover a wide range of additive manufacturing techniques. Typical forms of deformation of the processes laser sintering, laser beam melting and 3D printing (powder-binder) are presented and compensation strategies are discussed. Finally, an outlook on the ongoing research is given.

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Purpose The purpose of this work is to explain the emergence of warpage due to a locally and temporally inhomogeneous shrinkage in 3D printing (Binder-Jetting) of polymers. Design/methodology/approach An analysis of shrinkage yields parameters for a one-dimensional layer model of the binding process. Based on this, residual stresses and deformation are calculated by means of a numerical simulation model. Findings The simulation supports the assumption that the curling of specimens is created by a force transmission between layers due to inhomogeneous shrinkage. Furthermore, the layered production process might contribute to nonlinear deformations of not horizontally orientated surfaces. Research limitations/implications The simulation allows imitating the warping during the manufacturing process qualitatively. Exact values of deformations cannot be predicted, yet. Practical implications The results expand the knowledge about warpage effects in 3D printing caused by the layer-wise building process. Originality/value The developed model imitates the mechanisms leading to deformations during the 3D printing process, focusing on the physical interaction of layers with each other.

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