scholarly journals A Tolerance Analysis Approach Based on Robot Kinematics

2011 ◽  
Vol 2-3 ◽  
pp. 352-357
Author(s):  
Xiu Heng Zhang ◽  
Hong Yi Liu ◽  
Zhong Luo
Keyword(s):  
Three Dimensional ◽  
Mathematical Expression ◽  
Tolerance Analysis ◽  
Analysis Approach ◽  
Robot Kinematics ◽  
Small Displacement ◽  
Functional Requirement ◽  
Percentage Contribution ◽  
Cad Cam ◽  
Functional Features

This paper presents a tolerance modeling approach based on robot kinematics theory within CAD/CAM system. Based on the differential kinematics theories, each feature of characteristics including size tolerance and geometrical tolerance was established as a corresponding small displacement torsor. In order to express the relation between the small displacement of all functional features and the functional requirement, the final expression was represented to establish the projection of analysis of the tolerance chain. A mathematical expression was obtained by the mean instead of single points, and the constraints can be represented by interval using the standard deviation, not limit deviations. After having identified the unit components and the functional requirement from the tolerance chain, we obtained the percentage contribution of each unit feature to the functional requirement. A percentage contribution can help designer to decide which tolerance is tighten or loosen. The application of the tolerance analysis approach in a simple three-dimensional sample was also discussed in this paper.

A New Approach to Assemble Tolerance Analysis Based on CE/TOL

2014 ◽  
Vol 852 ◽  
pp. 634-638
Author(s):  
Xiu Heng Zhang ◽  
Peng Ba
Keyword(s):  
Three Dimensional ◽  
Tolerance Analysis ◽  
Functional Requirement ◽  
Modeling Tools ◽  
Manufacturing Costs ◽  
New Approach ◽  
Percentage Contribution ◽  
Technical Requirements ◽  
Processing Program ◽  
Mechanical Products

Quality indicators (precision, durability, reliability) of the mechanical products are heavily depended on their tolerance to select reasonable. According to the technical requirements and the processing program of the product in whole or in parts, the parts and components can be allocated on a reasonably tolerance, and the balance can be found between the product's features and manufacturing costs. In this paper, Pro / E modeling tools are used to design parts and assembly. In the assembly process, assembly of components designed is analyzed and synthezed by the using of CE/TOL (tolerance analysis) module of Pro/E. we obtained the percentage contribution of each unit feature to the functional requirement. A percentage contribution can help designer to decide which tolerance is tighten or loosen. The application of the tolerance analysis approacch in a simple three-dimensional sample was also discussed in this paper. Results show that this approach makes manufacturing costs and the probability of excessive interference and accuracy reduce. The accuracy of the product is improved.

Application of a Unified Jacobian—Torsor Model for Tolerance Analysis

2003 ◽  
Vol 3 (1) ◽  
pp. 2-14 ◽  
Author(s):  
Alain Desrochers ◽  
Walid Ghie ◽  
Luc Laperrie`re
Keyword(s):  
Three Dimensional ◽  
Tolerance Analysis ◽  
Small Displacement ◽  
Manufacturing Processes ◽  
Functional Requirements ◽  
Tolerance Zone ◽  
Kinematic Chains ◽  
Final Assembly ◽  
Novel Method ◽  
Assembly Constraints

Because of uncertainties in manufacturing processes, a mechanical part always shows variations in its geometrical characteristics (ex. form, dimension, orientation and position). Quality then often reflect how well tolerances and hence, functional requirements, are being achieved by the manufacturing processes in the final product. From a design perspective, efficient methods must be made available to compute, from the tolerances on individual parts, the value of the functional requirement on the final assembly. This is known as tolerance analysis. To that end, existing methods, often based on modeling of the open kinematic chains in robotics, are classified as deterministic or statistical. These methods suppose that the assembled parts are not perfect with regard to the nominal geometry and are rigid. The rigidity of the parts implies that the places of contacts are regarded as points. The validation or the determination of a tolerance zone is therefore accomplished by a series of simulation in specific points subjected to assembly constraints. To overcome the limitations and difficulties of point based approaches, the paper proposes the unification of two existing models: the Jacobian’s matrix model, based on the infinitesimal modeling of open kinematic chains in robotics, and the tolerance zone representation model, using small displacement screws and constraints to establish the extreme limits between which points and surfaces can vary. The approach also uses interval algebra as a novel method to take tolerance boundaries into account in tolerance analysis. The approach has been illustrated on a simple two parts assembly, nevertheless demonstrating the capability of the method to handle three-dimensional geometry. The results are then validated geometrically, showing the overall soundness of the approach.

A small displacement torsor model for 3D tolerance analysis of conical structures

2014 ◽  
Vol 229 (14) ◽  
pp. 2514-2523 ◽  
Author(s):  
Sun Jin ◽  
Hua Chen ◽  
Zhimin Li ◽  
Xinmin Lai
Keyword(s):  
Three Dimensional ◽  
Tolerance Analysis ◽  
Dimensional Euclidean Space ◽  
Small Displacement ◽  
Analysis Method ◽  
Tolerance Zone ◽  
Geometric Tolerances ◽  
Small Displacement Torsor ◽  
Conical Surfaces ◽  
Conical Structures

The small displacement torsor model is a classic three-dimensional tolerance analysis method. It uses three translational vectors and three rotational vectors to represent tolerance information in three-dimensional Euclidean space. However, the target features of this model mainly focused on planes and cylinders in previous studies. Little attention is invested to conical features and their joints which are used widely and more complex than the planar and cylindrical features. The objective of this article is to present a three-dimensional mathematical method of tolerance representation about conical surfaces and their joints based on the small displacement torsor model, and propose a mathematical model of variations and constraint relations of components of the small displacement torsor for conical surfaces caused by geometric tolerances limited by its tolerance zone. In addition, a simple example involving conical structures is used to demonstrate three-dimensional conical tolerance propagation. Both deterministic and statistical results are obtained by this model.

Dimensional Analysis of the Generated Design Solutions for Reconfigurable Manufacturing System

2013 ◽  
Author(s):  
Aamer Baqai ◽  
Arsalan Shafiq
Keyword(s):  
Manufacturing Systems ◽  
Performance Indicator ◽  
Three Dimensional ◽  
Tolerance Analysis ◽  
Machining Process ◽  
Small Displacement ◽  
Reconfigurable Manufacturing Systems ◽  
Reconfigurable Manufacturing ◽  
Design Solutions ◽  
Geometric Variation

Reconfigurable Manufacturing Systems (RMS) is the recent addition in the series of different of types manufacturing systems. Various approaches deal with generation of design solutions for such systems. In this paper two and three dimensional tolerance analysis of the generated design solutions using algorithmic approach for reconfigurable manufacturing systems is carried out. In this analysis quality is considered as the key performance indicator. Among the existing techniques and methods used for tolerance evaluation, the approach of representing the tolerances as Small Displacement Torsors (SDT) is used. The modified method of graphs is selected for representing the machining process plans among the existing methods. Heuristics for the said graphs are defined. For each geometric variation the torsors are written. 2D or 3D dimensional simulation is performed and solutions are classified according to their tolerance values. The proposed methodology has wide application in the generative approach of process plan generation for reconfigurable manufacturing systems.

Milling Fixture Design: A Tolerance Analysis Approach

2009 ◽  
Vol 37 (2) ◽  
pp. 111-117 ◽  
Author(s):  
Yongyooth Sermsuti-Anuwat
Keyword(s):  
Tolerance Analysis ◽  
Tolerance Allocation ◽  
Analysis Approach ◽  
Fixture Design ◽  
Functional Requirement ◽  
Specification Limits ◽  
Metal Machining ◽  
Jigs And Fixtures ◽  
Basic Equations

Jigs and fixtures are essential for metal machining. In their designs, the sizing of these components of work holding devices requires a great deal of experience and careful judgment. This paper describes an application of loop equations for tolerance allocation in jig and fixture design. The technique makes use of two basic equations, for sizes and for tolerances, to relate all functional dimensions to a functional requirement. This can simplify and facilitate the design of specification limits for jig and fixture components. The implementation of the technique is illustrated through a simple example of a milling fixture.

scholarly journals Development of a time-series shotgun metagenomics database for monitoring microbial communities at the Pacific coast of Japan

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kazutoshi Yoshitake ◽  
Gaku Kimura ◽  
Tomoko Sakami ◽  
Tsuyoshi Watanabe ◽  
Yukiko Taniuchi ◽  
...  
Keyword(s):  
Time Series ◽  
Microbial Communities ◽  
Pacific Coast ◽  
Three Dimensional ◽  
Amplicon Sequencing ◽  
Metagenomic Data ◽  
Shotgun Metagenomics ◽  
Functional Features ◽  
Pacific Coast Of Japan ◽  
Marine Microbial Communities

AbstractAlthough numerous metagenome, amplicon sequencing-based studies have been conducted to date to characterize marine microbial communities, relatively few have employed full metagenome shotgun sequencing to obtain a broader picture of the functional features of these marine microbial communities. Moreover, most of these studies only performed sporadic sampling, which is insufficient to understand an ecosystem comprehensively. In this study, we regularly conducted seawater sampling along the northeastern Pacific coast of Japan between March 2012 and May 2016. We collected 213 seawater samples and prepared size-based fractions to generate 454 subsets of samples for shotgun metagenome sequencing and analysis. We also determined the sequences of 16S rRNA (n = 111) and 18S rRNA (n = 47) gene amplicons from smaller sample subsets. We thereafter developed the Ocean Monitoring Database for time-series metagenomic data (http://marine-meta.healthscience.sci.waseda.ac.jp/omd/), which provides a three-dimensional bird’s-eye view of the data. This database includes results of digital DNA chip analysis, a novel method for estimating ocean characteristics such as water temperature from metagenomic data. Furthermore, we developed a novel classification method that includes more information about viruses than that acquired using BLAST. We further report the discovery of a large number of previously overlooked (TAG)n repeat sequences in the genomes of marine microbes. We predict that the availability of this time-series database will lead to major discoveries in marine microbiome research.

scholarly journals Virtual Surgical Planning, Stereolitographic Models and CAD/CAM Titanium Mesh for Three-Dimensional Reconstruction of Fibula Flap with Iliac Crest Graft and Dental Implants

2021 ◽  
Vol 10 (9) ◽  
pp. 1922
Author(s):  
Carlos Navarro Cuéllar ◽  
Manuel Tousidonis Rial ◽  
Raúl Antúnez-Conde ◽  
Santiago Ochandiano Caicoya ◽  
Ignacio Navarro Cuéllar ◽  
...  
Keyword(s):  
Bone Resorption ◽  
Surgical Planning ◽  
Iliac Crest ◽  
Three Dimensional ◽  
Titanium Mesh ◽  
Iliac Crest Graft ◽  
Virtual Surgical Planning ◽  
Fibula Flap ◽  
Dimensional Reconstruction ◽  
Cad Cam

Mandibular reconstruction with fibula flap shows a 3D discrepancy between the fibula and the remnant mandible. Eight patients underwent three-dimensional reconstruction of the fibula flap with iliac crest graft and dental implants through virtual surgical planning (VSP), stereolitographic models (STL) and CAD/CAM titanium mesh. Vertical ridge augmentation and horizontal dimensions of the fibula, peri-implant bone resorption of the iliac crest graft, implant success rate and functional and aesthetic results were evaluated. Vertical reconstruction ranged from 13.4 mm to 10.1 mm, with an average of 12.22 mm. Iliac crest graft and titanium mesh were able to preserve the width of the fibula, which ranged from 8.9 mm to 11.7 mm, with an average of 10.1 mm. A total of 38 implants were placed in the new mandible, with an average of 4.75 ± 0.4 implants per patient and an osseointegration success rate of 94.7%. Two implants were lost during the osseointegration period (5.3%). Bone resorption was measured as peri-implant bone resorption at the mesial and distal level of each implant, with a variation between 0.5 mm and 2.4 mm, and with a mean of 1.43 mm. All patients were rehabilitated with a fixed implant prosthesis with good aesthetic and functional results.

A CAD/CAM Representation Model Applied to Tolerance Transfer Methods

1998 ◽  
Author(s):  
Alain Desrochers
Keyword(s):  
Three Dimensional ◽  
Dimensional Representation ◽  
One Dimensional ◽  
Dimensional Tolerance ◽  
Representation Model ◽  
Three Dimensional Representation ◽  
Tolerance Chart ◽  
Cad Cam ◽  
Tolerance Charts

Abstract This paper presents the adaptation of tolerance transfer techniques to a model called TTRS for Technologically and Topologically Related Surfaces. According to this model, any three-dimensional part can be represented as a succession of surface associations forming a tree. Additional tolerancing information can be associated to each TTRS represented as a node on the tree. This information includes dimensional tolerances as well as tolerance chart values. Rules are then established to simulate tolerance chains or stack up along with tolerance charts directly from the graph. This way it becomes possible to combine traditional one dimensional tolerance transfer techniques with a powerful three-dimensional representation model providing high technological contents.

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