Computer-Aided Linear Tolerance Analysis and Optimal Tolerance Distribution for Cylindrical Machined Parts

1998 ◽  
Author(s):  
Jhy-Cherng Tsai ◽  
Chin-Ming Shih
Keyword(s):  
Tolerance Analysis ◽  
Optimization Techniques ◽  
Worst Case ◽  
Tolerance Chart ◽  
Computer Aided ◽  
Machined Parts ◽  
Cylindrical Parts ◽  
Statistical Tolerance ◽  
Tolerance Distribution ◽  
Tolerance Accumulation

Abstract Quality and cost are among the most important concerns for a product. While tolerance is one of the typical metrics for quality, it is a trade-off between tolerances and costs in product development though the two factors often conflict with each other. This paper describes a systematic approach to compute linear tolerance accumulation for cylindrical parts by machining operations based on the tolerance chart. A computer-aided tolerance chart system is developed to assist the construction of the corresponding tolerance chart and the computation of accumulated linear tolerances for a given process plan. Tolerance distribution to each machining operation by optimization techniques is also investigated. The goal is to minimize machining cost subject to constraints on tolerance accumulation and process capability. It shows that the machining cost of a sample part with the worst-case tolerance analysis can be reduced by 39%, compared to that by experience, and can be further reduced if statistical tolerance analysis applies.

Automation of Linear Tolerance Charts and Extension to Statistical Tolerance Analysis

2003 ◽  
Author(s):  
Zhengshu Shen ◽  
Jami J. Shah ◽  
Joseph K. Davidson
Keyword(s):  
Statistical Analysis ◽  
Tolerance Analysis ◽  
Automated Analysis ◽  
Worst Case Analysis ◽  
Worst Case ◽  
Tolerance Charting ◽  
Tolerance Charts ◽  
Statistical Tolerance ◽  
Tolerance Accumulation ◽  
Statistical Tolerance Analysis

Manual construction of tolerance charts is a popular technique for analyzing tolerance accumulation in parts and assemblies. But this technique has some limitations: (1) it only deals with the worst-case analysis, and not statistical analysis (2) it is time-consuming and errorprone (3) it considers variations in only one direction at a time, i.e. radial or linear. This paper proposes a method to automate 1-D tolerance charting, based on the ASU GD&T global model and to add statistical tolerance analysis functionality to the charting analysis. The automation of tolerance charting involves automation of stackup loop detection, automatic application of the rules for chart construction and determination of the closed form function for statistical analysis. The automated analysis considers both dimensional and geometric tolerances defined as per the ASME Y14.5 – 1994 standard at part and assembly level. The implementation of a prototype charting analysis system is described and two case studies are presented to demonstrate the approach.

Parametric Kinematic Tolerance Analysis of Planar Pairs With Multiple Contacts

1996 ◽  
Author(s):  
Elisha Sacks ◽  
Leo Joskowicz
Keyword(s):  
Efficient Algorithm ◽  
Tolerance Analysis ◽  
Parametric Model ◽  
Worst Case ◽  
Multiple Contacts ◽  
Work Cycle ◽  
Computer Aided ◽  
Kinematic Models ◽  
Range Of Variation ◽  
Different Parts

Abstract We present an efficient algorithm for worst-case limit kinematic tolerance analysis of planar kinematic pairs with multiple contacts. The algorithm extends computer-aided kinematic tolerance analysis from mechanisms in which parts interact through permanent contacts to mechanisms in which different parts or part features interact at different stages of the work cycle. Given a parametric model of a pair and the range of variation of the parameters, it constructs parametric kinematic models for the contacts, computes the configurations in which each contact occurs, and derives the sensitivity of the kinematic variation to the parameters. The algorithm also derives qualitative variations, such as under-cutting, interference, and jamming. We demonstrate the algorithm on a 26 parameter model of a Geneva mechanism.

Algebraic Representation of Geometric and Size Tolerances

1995 ◽  
Author(s):  
S. H. Mullins ◽  
D. C. Anderson
Keyword(s):  
Tolerance Analysis ◽  
Design Analysis ◽  
Algebraic Representation ◽  
Dimensional Metrology ◽  
Algebraic Form ◽  
Worst Case ◽  
Mechanical Component ◽  
Analysis And Synthesis ◽  
Statistical Tolerance ◽  
Statistical Tolerance Analysis

Abstract Presented is a method for mathematically modeling mechanical component tolerances. The method translates the semantics of ANSI Y14.5M tolerances into an algebraic form. This algebraic form is suitable for either worst-case or statistical tolerance analysis and seeks to satisfy the requirements of both dimensional metrology and design analysis and synthesis. The method is illustrated by application to datum systems, position tolerances, orientation tolerances, and size tolerances.

Statistical Tolerance Analysis of Over-Constrained Mechanical Assemblies With Form Defects Considering Contact Types

2019 ◽  
Vol 19 (2) ◽  
Author(s):  
Edoh Goka ◽  
Lazhar Homri ◽  
Pierre Beaurepaire ◽  
Jean-Yves Dantan
Keyword(s):  
Tolerance Analysis ◽  
Optimization Methods ◽  
Optimization Techniques ◽  
Behavior Modeling ◽  
Functional Requirements ◽  
Mechanical Assembly ◽  
Mechanical Assemblies ◽  
Statistical Tolerance ◽  
The Individual ◽  
Statistical Tolerance Analysis

Tolerance analysis aims toward the verification impact of the individual tolerances on the assembly and functional requirements of a mechanism. The manufactured products have several types of contact and are inherent in imperfections, which often causes the failure of the assembly and its functioning. Tolerances are, therefore, allocated to each part of the mechanism in purpose to obtain an optimal quality of the final product. Three main issues are generally defined to realize the tolerance analysis of a mechanical assembly: the geometrical deviations modeling, the geometrical behavior modeling, and the tolerance analysis techniques. In this paper, a method is proposed to realize the tolerance analysis of an over-constrained mechanical assembly with form defects by considering the contacts nature (fixed, sliding, and floating contacts) in its geometrical behavior modeling. Different optimization methods are used to study the different contact types. The overall statistical tolerance analysis of the over-constrained mechanical assembly is carried out by determining the assembly and the functionality probabilities based on optimization techniques combined with a Monte Carlo simulation (MCS). An application to an over-constrained mechanical assembly is given at the end.

Worst Case Tolerance Analysis with Nonlinear Problems

1988 ◽  
Vol 110 (3) ◽  
pp. 232-235 ◽  
Author(s):  
W. H. Greenwood ◽  
K. W. Chase
Keyword(s):  
Iterative Method ◽  
Significant Influence ◽  
Three Dimensional ◽  
Nonlinear Problems ◽  
Tolerance Analysis ◽  
Rational Basis ◽  
Worst Case ◽  
Manufactured Products ◽  
Engineering Drawings ◽  
Tolerance Accumulation

When designers assign tolerances on engineering drawings, they have a significant influence on the resulting cost and producibility of manufactured products. A rational basis for assigning tolerances involves constructing mathematical models of tolerance accumulation in assemblies of parts. However, tolerance stacks in two or three-dimensional problems or other nonlinear assembly functions may distort the resultant assembly tolerances, altering the range and symmetry. An iterative method is described for adjusting the nominal dimensions of the component parts such that the specified assembly limits are not violated.

A Design-and-Build Project to Introduce Concepts Relating to Dimensional Variation

1998 ◽  
Vol 26 (4) ◽  
pp. 259-272
Author(s):  
S. M. Panton ◽  
P. R. Milner
Keyword(s):  
Classroom Environment ◽  
Tolerance Analysis ◽  
Cylinder Block ◽  
Worst Case ◽  
Good Design ◽  
Minimum Number ◽  
Dimensional Variation ◽  
Assembly Problem ◽  
Statistical Tolerance ◽  
Statistical Tolerance Analysis

A design-and-build project which has been used to introduce Year 2 students of Mechanical Engineering to the concepts of dimensional variation and the influence of dimensional variation on function and assembly. The project simulates the cylinder head cylinder block assembly problem and specifies requirements in terms of a tolerance on concentricity of the cylinders in the head and block, and the interchangeable assembly of the head and block. Materials which are easily and cheaply sourced and tools which are easily manufactured and safe to use in a classroom environment are used throughout. During the project the students are exposed to concepts such as worst-case and statistical tolerance analysis, sensitivity analysis, geometric moment effects, minimum constraint design, co-variance and gauging. The exercise also emphasizes that good design means components that function and assemble with the minimum number of tight tolerances.

scholarly journals Cross-Domain Tolerance Analysis for Directional Control Valves Based on Imperfect Information

2018 ◽  
Vol 885 ◽  
pp. 276-289
Author(s):  
Ralf Tautenhahn ◽  
Jürgen Weber
Keyword(s):  
Imperfect Information ◽  
Tolerance Analysis ◽  
Product Characteristics ◽  
Worst Case ◽  
Control Valves ◽  
Cross Domain ◽  
Directional Control ◽  
Statistical Tolerance ◽  
Available Information ◽  
Noise Factors

The task of tolerance analysis usually addresses the question of the mechanical mountability of an assembly. We extend this viewpoint when talking about directional control valves in a crossdomain tolerance analysis; an analysis whose task is to determine the possible variation in the key product characteristics induced by a specific tolerance concept. As the available information about the noise factors to be toleranced is almost always imperfect generalised methods for their representation and the propagation of their impact on the key product characteristics are required. In this study the capabilities and potentials of belief and plausibility measures as well as fuzzy random variables are compared to traditional worst-case and statistical tolerance analysis.

A Nonlinear Tolerance Analysis Method Using Worst-Case and Matlab

2011 ◽  
Vol 201-203 ◽  
pp. 247-252
Author(s):  
Mei Qiong Yu ◽  
Yan Yan ◽  
Jia Hao ◽  
Guo Xin Wang
Keyword(s):  
Mathematical Formulation ◽  
Tolerance Analysis ◽  
Worst Case Analysis ◽  
Analysis Method ◽  
Worst Case ◽  
Analysis Methods ◽  
Precision Design ◽  
Basic Parameters ◽  
Statistical Tolerance ◽  
Production Requirement

The tolerance analysis methods are usually used to test the result of product design and assembly; moreover the tolerance analysis also is a fundamental technique in precision design process. So far, there are two kinds of tolerance analysis methods: statistical tolerance analysis and worst-case analysis; they have their own characteristics and drawbacks. In this paper, it presents a nonlinear tolerance analysis method which uses Matlab tool to construct the nonlinear tolerance analysis mathematical formulation and calculate the result of nonlinear tolerance analysis based on the principle of worst-case tolerance analysis. All the processes are dealt with and tested by computer. The engineers only enter some basic parameters through the standardized interface, and then the result can be obtained without artificial intervention. In addition, the accuracy of calculation result meets the production requirement. The system of the nonlinear tolerance analysis is easier for engineers to use.

Validation of the Tolerance Analysis of Compliant Assemblies

1999 ◽  
Author(s):  
Eric Sellem ◽  
Alain Rivière ◽  
Charles André De Hillerin ◽  
André Clement
Keyword(s):  
Sensitivity Analysis ◽  
Mechanical Model ◽  
Tolerance Analysis ◽  
Assembly Process ◽  
Worst Case ◽  
Key Characteristics ◽  
Statistical Tolerance ◽  
Compliant Parts ◽  
Complex Parts ◽  
Statistical Tolerance Analysis

Abstract Current statistical tolerance analysis of assemblies are generally based on Monte Carlo simulation or Worst Case. The available software tools using this technique model the assembly of rigid parts, by only considering the kinematic laws. Sellem (1998) proposed a linear mechanical model taking both deformation and assembly process into account in the computation of tolerance assemblies of compliant parts. This paper presents the validation of this method by a comparison with measurements performed on an actual assembly of four complex parts. Some improvements in the modeling of the assembly process are also presented and described a sensitivity analysis approach to identify the key characteristics of the assembly.

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