A Volumetric Difference-based Adaptive Slicing and Deposition Method for Layered Manufacturing

2003 ◽  
Vol 125 (3) ◽  
pp. 586-594 ◽  
Author(s):  
Y. Yang ◽  
J. Y. H. Fuh ◽  
H. T. Loh ◽  
Y. S. Wong
Keyword(s):  
Local Features ◽  
Layered Manufacturing ◽  
Deposition Method ◽  
Adaptive Slicing ◽  
Surface Normal ◽  
Staircase Effect ◽  
Slicing Method ◽  
Cusp Height ◽  
The Difference ◽  
New Criterion

Adaptive slicing capable of producing variable thickness is a useful means to improve the fabrication efficiency in layered manufacturing (LM) or Rapid Prototyping (RP) processes. Many approaches have been reported in this field; however, most of them are based on the cusp height criteria, which is not an effective representation of the staircase effect when the surface normal is near vertical. Furthermore, most of the existing methods slice the model without considering the local features in the plane of the sliced layer. This paper introduces a novel difference-based adaptive slicing and deposition method. The advantage of this slicing method is that the slicing error is independent of the surface normal. A new criterion for adaptive slicing is evaluated and compared with that based on cusp-height. An adaptive slicing algorithm, which uses the volumetric difference between two adjacent layers as the criterion for slicing, has been developed in this work. Different deposition strategies for the common area and the difference area are applied to layer fabrication while considering the local features of the sliced layer. The algorithm has been tested with a sample part, and the results indicate that a better surface finish can be achieved for both surfaces whose normals are nearly in the slicing plane and surfaces whose normals are nearly perpendicular to the slicing plane. It is found that the building time can be reduced by 40% compared with the traditional adaptive slicing. The proposed method has minimized the volumetric error between the built LM part and the original CAD model while achieving a higher efficiency. It is suitable for most commercialized LM systems due to its simplicity in implementation.

Adaptive Slicing of Parametrizable Algebraic Surfaces for Layered Manufacturing

1995 ◽  
Author(s):  
Prashant Kulkarni ◽  
Debasish Dutta
Keyword(s):  
Variable Thickness ◽  
Algebraic Surface ◽  
Layered Manufacturing ◽  
Algebraic Surfaces ◽  
Geometric Accuracy ◽  
Adaptive Slicing ◽  
Staircase Effect

Abstract As the various applications of Layered Manufacturing (LM) expand from just prototyping, the geometric accuracy issues become more prominent. Variable thickness, or adaptive, slicing aides in reducing a major source of geometric inaccuracy, the staircase effect. This paper develops a procedure for the adaptive slicing of a parametrizable algebraic surface to be manufactured by an LM process. An implemented example of the procedure is presented.

Volumetric Error Control in Layered Manufacturing

2014 ◽  
Author(s):  
Mohammad Taufik ◽  
Prashant Kumar Jain
Keyword(s):  
Layer Thickness ◽  
Surface Finish ◽  
Error Control ◽  
Layered Manufacturing ◽  
Volumetric Error ◽  
Adaptive Slicing ◽  
Inclined Surfaces ◽  
Novel Method ◽  
Cusp Height ◽  
Steep Slopes

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.

A novel adaptive slicing algorithm based on ameliorative area ratio and accurate cusp height for 3D printing

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yifei Hu ◽  
Xin Jiang ◽  
Guanying Huo ◽  
Cheng Su ◽  
Hexiong Li ◽  
...  
Keyword(s):  
3D Printing ◽  
Surface Quality ◽  
Three Dimensional ◽  
Geometric Error ◽  
Area Ratio ◽  
Adaptive Slicing ◽  
Content Type ◽  
Contour Matching ◽  
Slicing Method ◽  
Cusp Height

Purpose Adaptive slicing is a key step in three-dimensional (3D) printing as it is closely related to the building time and the surface quality. This study aims to develop a novel adaptive slicing method based on ameliorative area ratio and accurate cusp height for 3D printing using stereolithography (STL) models. Design/methodology/approach The proposed method consists of two stages. In the first stage, the STL model is sliced with constant layer thickness, where an improved algorithm for generating active triangular patches, the list is developed to preprocess the model faster. In the second stage, the model is first divided into several blocks according to the number of contours, then an axis-aligned bounding box-based contour matching algorithm and a polygons intersection algorithm are given to compare the geometric information between several successive layers, which will determine whether these layers can be merged to one. Findings Several benchmarks are applied to verify this new method. Developed method has also been compared with the uniform slicing method and two existing adaptive slicing methods to demonstrate its effectiveness in slicing. Originality/value Compared with other methods, the method leads to fewer layers whilst keeping the geometric error within a given threshold. It demonstrates that the proposed slicing method can reach a trade-off between the building time and the surface quality.

Volumetric adaptive slicing of manifold mesh for rapid prototyping based on relative volume error

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Qianyong Chen ◽  
Jinghua Xu ◽  
Shuyou Zhang
Keyword(s):  
Rapid Prototyping ◽  
Surface Quality ◽  
Relative Volume ◽  
Confocal Laser ◽  
Adaptive Slicing ◽  
Content Type ◽  
Layer Height ◽  
Part Surface ◽  
Slicing Method ◽  
Cusp Height

Purpose Compared with cusp height and area deviation ratio, volume error (VE) caused by the layer height could represent the stair-case effect more comprehensively. The proposed relative volume error (RVE)-based adaptive slicing method takes VE rather than cusp height as slicing criteria, which can improve part surface quality for functionalized additive manufacturing. Design/methodology/approach This paper proposes a volumetric adaptive slicing method of manifold mesh for rapid prototyping based on RVE. The pre-height sequences of manifold mesh are first preset to reduce the SE by dividing the whole layer sequence into several parts. A breadth-first search-based algorithm has been developed to generate a solid voxelization to get VE. A new parameter RVE is proposed to evaluate the VE caused by the sequence of the layer positions. The RVE slicing is conducted by iteratively adjusting the layer height sequences under different constraint conditions. Findings Three manifold models are used to verify the proposed method. Compared with uniform slicing with 0.2 mm layer height, cusp height-based method and area deviation-based method, the standard deviations of RVE of all three models are improved under the proposed method. The surface roughness measured by the confocal laser scanning microscope proves that the proposed RVE method can greatly improve part surface quality by minimizing RVE. Originality/value This paper proposes an RVE-based method to balance the surface quality and print time. RVE could be calculated by voxelized parts with required accuracy at a very fast speed by parallel.

A Comparison of Two Different IMPSAT Models in Compositional Simulation

SPE Journal ◽  
2007 ◽  
Vol 12 (01) ◽  
pp. 145-151 ◽  
Author(s):  
Jarle Haukas ◽  
Ivar Aavatsmark ◽  
Magne Espedal ◽  
Edel Reiso
Keyword(s):  
Explicit Solution ◽  
Oil And Gas ◽  
Compositional Simulation ◽  
Flow Equations ◽  
Gas Phases ◽  
Compositional Model ◽  
The Difference ◽  
The Stability ◽  
New Criterion ◽  
Nonlinear Iteration

Summary A new IMPSAT model, with explicit solution of variables that are isochoric (i.e., complementary to volumes), is compared to the conventional IMPSAT model, which determines phase mole fractions explicitly. The compared properties are performance of the nonlinear iteration and numerical stability. The use of complementary variables in the new IMPSAT model makes the nonlinear system better conditioned. Consequently, fewer nonlinear iteration steps are required. The resulting speedup more than compensates for the added costs of introducing and using the isochoric variables. The stability criterion associated with the new IMPSAT model is in many cases significantly less conservative than the conventional criterion. However, for cases in which there is little or no saturation change between the hydrocarbon phases (e.g., for retrograde gas condensate cases or single hydrocarbon phase cases), the difference between the criteria is insignificant. The timestep sizes for which instabilities occur are practically the same for the two models, and no oscillations have been observed unless both the new and the conventional criterion are violated. Consequently, the stability properties are similar, and the new criterion seems to apply to both models. Our conclusions are supported by numerical results. Introduction An isothermal compositional model of Nc components involves the solution of Nc flow equations per gridblock (e.g., the mass balance equations): (Eq. 1) where ?ni is the change in the amount of component i during timestep ?t, while fi and qi are the component interblock flow and source rates. In addition, phase equilibrium between the oil and gas phases (e.g., equalities of fugacities), (Eq. 2) must be taken into account. Because of the large number of equations and the complex thermodynamics, it is too demanding to determine all variables implicitly (i.e., simultaneously in all gridblocks). Instead, we use a partially explicit approach, where some variables are determined implicitly, while others are determined explicitly, gridblock by gridblock. The explicit solution relies on explicit treatment of variables (i.e., evaluating parts of the interblock flow with variables from the previous time level).

Direct 3D Layer Metal Deposition and Toolpath Generation

2008 ◽  
Author(s):  
Jianzhong Ruan ◽  
Lie Tang ◽  
Todd E. Sparks ◽  
Robert G. Landers ◽  
Frank Liou
Keyword(s):  
Solid Freeform Fabrication ◽  
Deposition Method ◽  
Single Track ◽  
Uniform Thickness ◽  
Post Processing ◽  
Freeform Fabrication ◽  
Manufacturing Efficiency ◽  
Layer Deposition ◽  
Staircase Effect ◽  
Parallel Layer

Multi-axis slicing for solid freeform fabrication (SFF) manufacturing process can yield non-uniform thickness layers, or 3-D layers. Using the traditional parallel layer construction approach to build such a layer leads to a staircase which requires machining or other post processing to form the desired shape. This paper presents a direct 3-D layer deposition approach. This approach uses an empirical model to predict the layer thickness based on experimental data. The toolpath between layers is not parallel; instead, it follows the final shape of the designed geometry and the distance between the toolpath in the adjacent layers varies at different locations. Directly depositing a 3-D layer not only eliminates the staircase effect, but also improves the manufacturing efficiency by shortening the deposition and machining times. A single track deposition experiment has demonstrated these advantages. Thus, it is a beneficial addition to the traditional parallel deposition method.

scholarly journals Comparative Analysis of Genetically-Modified Crops: Conditional Equivalence Criteria

2021 ◽  
Author(s):  
Changjian Jiang ◽  
Chen Meng ◽  
Adam W. Schapaugh ◽  
Huizhe Jin
Keyword(s):  
Genetically Modified ◽  
Genetically Modified Crops ◽  
Genotypic Differences ◽  
Unintended Effects ◽  
Equivalence Test ◽  
History Of ◽  
Equivalence Criterion ◽  
The Difference ◽  
New Criterion ◽  
The Given

AbstractThe comparative assessment of genetically-modified (GM) crops relies on the principle of substantial equivalence, which states that such products should be compared to conventional counterparts that have an established history of safe use. In an effort to operationalize this principle, the GMO Panel of the European Food Safety Authority proposed an equivalence test that directly compares a GM test variety with a set of unrelated, conventionally-bred reference varieties with part of the difference as the known background of the test (the same as the given control). The criterion of the EFSA test, however, is defined solely by genotypic differences between the non-traited control and reference varieties (i.e. the background effect) while assuming the so-called GM trait effect as zero. As the outcome of an EFSA equivalence test is determined primarily by the similarity, or lack thereof, of the control and references, a conditional equivalence criterion is proposed in this investigation that focuses on “unintended” effects of a GM trait which is irrespective of the (random) genotypic value of a given control. The new criterion also includes a mean-scaled standard similar to the 80-125% rule for bioequivalence assessment practiced in the pharmaceutical industry as an alternative when the reference variation is zero or close to zero. In addition, optional criteria are proposed with a step-wise procedure to control the rate of false negatives (non-equivalence by chance) providing a comprehensive assessment under multiple comparisons. An application to maize grain composition data demonstrates that the conditional equivalence criterion provides effect-specific and more robust assessment of equivalence than the EFSA criterion did, especially for GM traits showing negligible or no unintended effects which are likely true for most traits in the current market.

scholarly journals An underspecification approach to Hausa resumption

2016 ◽  
Author(s):  
Berthold Crysmann
Keyword(s):  
Recent Work ◽  
Local Features ◽  
Division Of Labour ◽  
Single Feature ◽  
Pronoun Use ◽  
Non Local ◽  
Unbounded Dependency ◽  
The Difference ◽  
Treat All

Within recent work on the treatment of resumption in HPSG, there is growing consensus that resumptive unbounded dependency constructions (=UDCs) should be modelled on a par with gap-type UDCs (Alotaibi and Borsley, 2013; Borsley, 2010; Crysmann, 2012b; Taghvaipour, 2005), using a single feature for both types of dependencies, rather than separate features, as proposed by Vaillette (2001a,b). Yet, authors disagree as to where exactly in the grammar the resumptive function of pronominals should be established: while Crysmann (2012b, 2015) advances an ambiguity approach that has pronominal synsem objects being ambiguous between a resumptive and an ordinary pronoun use, Borsley (2010); Alotaibi and Borsley (2013), by contrast, treat all pronominals, resumptive or not, as ordinary pronouns and effect their resumptive use by means of tailoring the amalgamation principle to potentially include pronominal indices. While their decision provides a straightforward account of McCloskey’s generalisation that resumptives always look like the ordinary pronouns of the language, it fails to capture the difference in semantics between ordinary pronominal and resumptive uses. In this paper, I shall reexamine the evidence from Hausa and propose to synthesise the approaches put forth by Alotaibi and Borsley (2013) and Crysmann (2012b), and propose that the potential for pronominal and resumptive function (including their difference w.r.t. semantics and non-local features) is captured by means of underspecification, yet the decision as to canonical vs. non-canonical use is made at the level of the governing head (Borsley, 2010; Alotaibi and Borsley, 2013). I shall argue that this division of labour is sufficient to derive the correct gap-like semantics for resumptives, maintains standard deterministic amalgamation, and, finally, provides an answer to McCloskey’s generalisation.

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