From 3D Models to 3D Prints: an Overview of the Processing Pipeline <s> Uniform and adaptive slicing <s> Describes a new approach to fast layered manufacturing. The improvements in speed are achieved entirely through software control of existing commercial layered manufacturing equipment. In particular, the exterior regions of a part are built with thin layers to provide a precise, smooth exterior surface, while its interior regions are built with fast, thick layers to reduce overall build time. This approach has been implemented and tested with .STL CAD models on a Stratasys FDM 1600 rapid prototyping system, where a 50‐80 per cent reduction in build time of dense parts has been achieved without reducing surface quality or part integrity. <s> BIB001 </s> From 3D Models to 3D Prints: an Overview of the Processing Pipeline <s> Uniform and adaptive slicing <s> This paper presents a new approach to adaptive slicing that significantly reduces fabrication times. The new approach first identifies the individual parts and features that comprise each layer in a given build, and then slices each independently of one another. This technique improves upon existing adaptive slicing algorithms by eliminating most of the slices that do not effectively enhance the overall part surface quality. Conventional adaptive slicing methods produce unnecessary layers that contribute to increased fabrication times without improving the overall quality of the part surfaces. These unnecessary layers result from fabricating all of the parts and features within the build volume at a given height using a single build layer thickness. Each thickness is commonly derived from the one part or feature existing at that height whose surface geometry requires the thinnest layer to meet a tolerance criterion. The new approach has been implemented on an FDM 1600 rapid prototyping system, and has demonstrated a 17‐37 per cent reduction in fabrication times compared to that of conventional adaptive slicing methods. <s> BIB002 </s> From 3D Models to 3D Prints: an Overview of the Processing Pipeline <s> Uniform and adaptive slicing <s> We present a pipeline of algorithms that decomposes a given polygon model into parts such that each part can be 3D printed with high (outer) surface quality. For this we exploit the fact that most 3D printing technologies have an anisotropic resolution and hence the surface smoothness varies significantly with the orientation of the surface. Our pipeline starts by segmenting the input surface into patches such that their normals can be aligned perpendicularly to the printing direction. A 3D Voronoi diagram is computed such that the intersections of the Voronoi cells with the surface approximate these surface patches. The intersections of the Voronoi cells with the input model's volume then provide an initial decomposition. We further present an algorithm to compute an assembly order for the parts and generate connectors between them. A post processing step further optimizes the seams between segments to improve the visual quality. We run our pipeline on a wide range of 3D models and experimentally evaluate the obtained improvements in terms of numerical, visual, and haptic quality. <s> BIB003
The simplest approach to divide the object into slices is to subdivide it uniformly, as illustrated in Figure 11 , left. Given a manufacturing layer thickness τ and an object height H, the object is divided into N = H τ slices. Each slice i is then located at height z i = i+0.5 N , which is the position of the plane that will be intersected with the object. This approach is widely adopted and most software offer it as a standard approach. However, many objects have a shape that varies greatly along its height. Therefore, in some regions uniform slicing might use too many slices, while it does not properly capture the shape in others. In particular, surfaces that are slanted with respect to the build direction produce a staircase defect through additive manufacturing. These areas require to use very thin slices (small τ). Uniform slicing forces the same small value of τ to be used throughout the entire part, which produce a large number of slices and increases manufacturing time. Most technologies are able to change the layer height during manufacturing. Adaptive slicing approaches exploit this property, by adapting the thickness of each slice to the shape geometry, as illustrated in Figure 11 , middle. Given a model for the geometric error (see Section 2.2), these approaches refine or coarsen the slices to meet a quality constraint while reducing print time. This can be achieved by locally determining the slice thickness from the error [DM94, SW While adaptive slicing is able to adapt to shape changes along the build direction, it still cannot adapt to a change in part complexity within the layer. Consider an object with a vertical wall on the left, and a slanted surface on the right. The vertical wall could be printed with thick slices, however the slope on the right imposes the use of thin slices to limit the staircase effect. To reduce this issue, locally adaptive slicing has been proposed BIB002 . The key idea is to first subdivide the object into different regions, each region being sliced independently, as is illustrated in Figure 11 , right. Depending on the target technology, the different regions can be built together by locally changing the layer height [TB98, WCT * 15], or they can be printed independently and later assembled  BIB003 . The main issue with this approach is that seams appear along the surface where different layer thicknesses meet. For techniques where parts are printed separately a manual assembly step is required. Interestingly a similar approach was used on the object interior by BIB001 : Since the inside is never visible, it can be sliced using a larger thickness than the exterior.This idea can be combined with the aforementioned techniques, for instance performing local adaptive slicing only on the exterior shell while the interior uses the maximal thickness  .