From 3D Models to 3D Prints: an Overview of the Processing Pipeline <s> Form <s> Abstract The 1980s witnessed the emergence of new manufacturing technologies that build parts layer by layer. These layered-manufacturing techniques can significantly reduce the design-to-product leadtimes. The paper overviews several procedures for generating the layers from a cad model such that the resulting part can be accurately manufactured using LMT. <s> BIB001 </s> From 3D Models to 3D Prints: an Overview of the Processing Pipeline <s> Form <s> As more choices of materials and build processes become available in layered manufacturing (LM), it is increasingly important to identify fundamental problems that underlie the entire field. Determination of best build orientation and minimizing build cost of a part are two such issues that must be considered in any LM process. By decoupling the solution to these problems from a specific LM technology, not only can the solution be applied to a variety of processes, but more realistic cost comparisons of parts built on different machines become possible. <s> BIB002 </s> From 3D Models to 3D Prints: an Overview of the Processing Pipeline <s> Form <s> In any rapid prototyping process, the layer by layer building process introduces an error in the amount of material used compared to the volume specified by the computer-aided design model. This affects the dimensional accuracy as well as the surface finish for different part build orientations. This paper describes a methodology for computing the volumetric error for any orientation of the parts built by the fused deposition modelling rapid prototyping system. The technique can be applied to determine the best orientation of the part, based on the minimum volumetric error. The technique is verified by comparing the results with the experimental measurements of the volumetric errors of the parts built at different orientations. <s> BIB003 </s> From 3D Models to 3D Prints: an Overview of the Processing Pipeline <s> Form <s> This paper presents a novel method for adaptive slicing based on volumetric error considerations for Layered Manufacturing (LM). In the general LM process uses constant layer thickness throughout the part height which leads to poor surface finish at inclined surfaces. Therefore, adaptive slicing was proposed to control the surface roughness by adaptively selecting the layer thickness based on surface finish at a particular angle or slope of the surface. Most of the researchers used the cusp height concept for adaptive slicing. However, limitation of cusp height based adaptive slicing procedure is that, it does not have any direct control on volumetric error and it is quite possible that with a very little variation in cusp height a large variation in volumetric error may occur on steep slopes of surface. In the proposed work an algorithm is developed and implemented for adaptive slicing to control/select layer thickness based on user specified volumetric error/loss. A model is developed to calculate volumetric loss for the particular layer considering the geometry of the model.Copyright © 2014 by ASME <s> BIB004
In additive manufacturing objects are created by approximating a given design with a set of layers stacked one on top of the other along the build direction. The goal of form fidelity is to detect the difference in shape between these two entities. We present here the two most widely adopted metrics in literature to evaluate the error introduced by layered manufacturing: the cusp height error and the volumetric difference. • The cusp-height error concept was introduced in the context of adaptive slicing for layered manufacturing BIB001 . It is defined Approximating a curved surface with a stack of layers piled along the building direction introduces the typical staircase effect and reduces fidelity (a). As can be noticed nearly horizontal surfaces introduce more error than nearly vertical ones. Cusp height (b) and volumetric difference (c) are among the most widely used proxies to estimate fidelity. as the maximum distance between the manufactured part's surface and the design surface BIB002 . It depends on the layer thickness l and the angle θ between the local surface orientation and the build direction (Figure 2b ), namely Note that | cos θ| is very small for nearly orthogonal angles and grows up to 1 when θ is close to 0 degrees. This well encodes the big approximation error difference between nearly vertical and nearly horizontal surfaces, as shown in Figure 2a . The integral of the cusp height on the whole surface is a good estimator of the fidelity of the printed model. To this end, for triangulated surfaces the cusp height is computed separately on each facet as the dot product between the build direction b and the triangle normal n, | cos θ| = |b · n|. It is then scaled by the triangle area and normalized by the total mesh area so as to accommodate uneven tessellations and make it scale independent [WZK16]; • The volumetric difference is the difference between the volume enclosed by the design and the volume of the printed object (red area in Figure 2c ). In BIB003 Masood and colleagues explain how to evaluate the volumetric error for simple geometries such as cylinders, cubes, pyramids and spheres. Such work was then extended to complex geometries in [MRI03] . Notice that, although they are both used as proxies to minimize the staircase effect, volumetric difference and cusp height are not equivalent. Taufik and colleagues BIB004 express a preference for volumetric error. They observe that, if the shape to be printed contains steep slopes, to a little variation in cusp height may correspond a large variation in volumetric difference, thus making the latter more accurate than the former.