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Optimization of Machining Tolerance Allocation
Published in R. Saravanan, Manufacturing Optimization through Intelligent Techniques, 2017
The difference between these two problems is illustrated in Figure 5.6. In tolerance analysis, the component tolerances are all known or specified and the resulting assembly variation is calculated. On the other hand, in tolerance allocation, the assembly tolerance is known from design requirements, although the magnitudes of the component tolerances to meet these requirements are unknown. The available assembly tolerance must be distributed or allocated among the components in some rational way. The influence of the tolerance accumulation model and the allocation rule chosen by the designer on the resulting tolerance allocation will be demonstrated.
The Three-Dimensional Virtual Product
Published in Ali Jamnia, Introduction to Product Design and Development for Engineers, 2018
For mechanical systems, tolerance analysis is thought of as a process that studies relationships between the dimensions of various components within a given assembly. Relevant feature dimensions and their associated tolerances are added in a prescribed sequence in order to determine the upper and lower dimensional values of a target feature. Using this information, nominal gaps or interferences along with their associated tolerances are determined. Typical tools that are used in these calculations are worst-case analysis, root sum of squares method, or Monte Carlo analysis. Chapter 16 provides an in-depth review of tolerance analysis.
Building a prototype using off-the-shelf components
Published in Fuewen Frank Liou, Rapid Prototyping and Engineering Applications, 2019
Tolerance is also called the language of assemblies. Tolerance analysis can be used to increase understanding of part function, to discover and resolve problems on paper rather than in prototype or production, and to make intelligent design decisions.
A study of tolerance allocation and stack-up analysis to improve the assembly precision of an injection mold
Published in Journal of the Chinese Institute of Engineers, 2023
Yuo-Tern Tsai, Kuan-Hong Lin, Chun-Sheng Chen
Analytical models of tolerance analysis provide a quantitative evaluation of the design variations and the tolerance specifications. Tolerance analysis mainly discusses a model describing the closed loop of the work pieces combined and determines the tolerance sizes of the combinations. The main functions of tolerance analysis are to calculate the tolerance sizes of an assembly based on the closed loop of the dimensional chain. The simpler the closed loop is, the better the tolerance analysis in evaluating the assembly variation. A good model of tolerance analysis can predict how much the tolerance can match the actual limits of working precision. Engineers are usually more concentrated on the problems of tolerance allocation rather than tolerance analysis while performing tolerance designing (Chase 1999).
Surface fairness: a quality metric for aesthetic assessment of compliant automotive bodies
Published in Journal of Engineering Design, 2018
Ali Hashemian, Behnam Moetakef Imani
Nowadays, the most important objectives in automotive manufacturing industry can be categorised as follows: the reduction for production cost, increasing the overall quality and performance, decreasing the lead time and ensuring customer satisfaction. The propagation of dimensional and geometric tolerances through the assembly process would affect the quality and overall performance of products. Therefore, it is crucial to have a comprehensive model for analysing the relationship between the input tolerances and the final responses of the assembly. The tolerance analysis is an important link between design and manufacture which generally aims at predicting variation in one or several critical dimensions or features of the product with respect to manufacturing or assembling tolerances (Chase and Parkinson 1991). It can significantly shorten the design time and reduce the need for any physical prototyping based on statistical tolerance data. In addition, tolerance analysis can evaluate the quality of products and conduct quality audits in early stages of the design process.
Direct tolerance analysis of mechanical assemblies with normal and non-normal tolerances for predicting product quality
Published in International Journal of Computer Integrated Manufacturing, 2022
The conventional tolerance analysis methods generally use the worst case (WC) and root-sum squares (RSS) approaches for tolerance stack-up to estimate the tolerance accumulation on the assembly dimensions. Also, the conventional methods in the literature have been developed based on these main limitations that the assembly function is available in an explicit form and the dimensions are varied under the normality assumption. Therefore, to deal with these problems, a new tolerance analysis method was introduced based on the univariate DR method and the Pearson system. The proposed method can nonlinear tolerance analysis of the mechanical assembly without the need for existing the explicit assembly function. In addition, according to the proposed method, the dimensions can be varied under normal or non-normal distributions. The proposed approach was applied to tolerance analysis of some case studies and results were compared to improved-HLRF reliability index and MCS approaches. Results showed that the proposed approach can present more efficient results than the two other methods. The number of function evaluations in the proposed method to estimate the rejected product rate was much less than the other two methods. Unlike the conventional methods in the literature such as RSS and MCS, the proposed approach, is an accurate and efficient method to handle the tolerances that are distributed normally and non-normal without needing an explicit assembly function. It should be noted that the proposed method does not need any sensitivity analysis, so it is more efficient and practical in actual high-dimensional mechanical assemblies. The proposed algorithm can be easily automated to be used within CAD/CAM software for assembly quality control in industrial applications.