Tolerance analysis and optimization based on 3DCS

At present, with the increasing requirements of major enterprises on assembly accuracy, the problem of interference and excessive clearance between parts needs to be solved. In order to analyze and optimize the tolerances in the actual assembly of the parts, a three-dimensional vector ring model is proposed on the basis of the dimensional chain model, and the tolerance distribution is optimized by the “dichotomy method”. With the help of 3DCS, the virtual assembly of the automobile headlight is carried out, and the sensitivity analysis is carried out by establishing the measurement of the gap between the turn signal and headlight in the automobile headlight, and the simulation results are used to obtain a reasonable improvement in tolerance allocation that meets the design criteria and saves costs. The results are compared with the traditional method of optimizing the allocation of equal tolerances and are clearly superior, providing a method for optimizing the allocation of tolerances to parts in engineering practice.

Knowledge creation and application of optimal tolerance distribution method for aircraft product assembly

Purpose This paper aims to illustrate the tolerance optimization method based on the assembly accuracy constrain, precession constrain and the cost of production of the assembly product. Design/methodology/approach A tolerance optimization method is an excellent way to perform product assembly performance. The tolerance optimization method is adapted to the process analysis of the hatch and skin of an aircraft. In this paper, the tolerance optimization techniques are applied to the tolerance allocation for step difference analysis (example: step difference between aircraft cabin door and fuselage outer skin). First, a mathematical model is described to understand the relationship between manufacturing cost and tolerance cost. Second, the penalty function method is applied to form a new equation for tolerance optimization. Finally, MATLAB software is used to calculate 170 loops iteration to understand the efficiency of the new equation for tolerance optimization. Findings The tolerance optimization method is based on the assembly accuracy constrain, machinery constrain and the cost of production of the assembly product. The main finding of this paper is the lowest assembly and lowest production costs that met the product tolerance specification. Research limitations/implications This paper illustrated an efficient method of tolerance allocation for products assembly. After 170 loops iterations, it founds that the results very close to the original required tolerance. But it can easily say that the different number of loops iterations may have a different result. But optimization result must be approximate to the original tolerance requirements. Practical implications It is evident from Table 4 that the tolerance of the closed loop is 1.3999 after the tolerance distribution is completed, which is less than and very close to the original tolerance of 1.40; the machining precision constraint of the outer skin of the cabin door and the fuselage is satisfied, and the assembly precision constraint of the closed loop is satisfied. Originality/value The research may support further research studies to minimize cost tolerance allocation using tolerance cost optimization techniques, which must meet the given constrain accuracy for assembly products.

Differences of Total Activity and Heat Tolerance of Complement in Plasma Between Black and Yellow Populations

Background The goal of this paper is to compare and evaluate the differences in total activity and Heat Tolerance of complement distribution Between Black and Yellow populations.Methods Blood samples of Black and Yellow healthy individuals were randomly collected, and plasma was obtained. The test plasma was diluted in a five series concentration, following with standard reaction and experimental reaction measurements. The basic principle of heat tolerance temperature calculation is to consider the ratio value (ratio method) in which heat tolerance of TCA calculated and plotted according to the area of trapezoidal and triangle as follows: C x°C=OD1-OD5+(OD2-OD5+OD3-OD5+OD4-OD5)*2. Where Cx°C is the total complement activity of the specimen measured in the two reaction conditions.Results The total activity of complement in Black individuals was statistically significantly lower than Yellow individuals (P< 0.05). The heat tolerance of total complement activity was higher among blacks than yellow individuals with no differences between the two groups (P> 0.05). The frequency values of total activity of complement distributed in the yellow individuals was statistically higher than Blacks (P<0.05) and The heat tolerance of total complement activity was statistically higher significant among Blacks than Yellow individuals (P<0.05).Conclusions There is a high differences in total complement activity and heat Tolerance distribution between Black and Yellow populations, may predict health status and innate immunity level differences between African race and Asian race.

The Method of Tolerance Analysis Base on the Monte Carlo

The primary goal of concurrent engineering is to minimize the time spend and to reduce quality problems encountered between a product's conception and customer use, thereby minimizing cost and maximizing product quality. Tolerance is an important index of product design and manufacture. Although they are small as compared with part dimensions, tolerances can propagate and accumulate in an assembly affecting the product assimilability. Moreover, tolerance is inevitable because manufacturing exactly equal parts is known to be impossible. This paper presents a brief review of statistical tolerance and clearance analysis for the assembly, and proposes a method of tolerance analysis by a leading commercial computer-aided tolerance (CAT) analysis system, VisVSA. This method can ensure assembly precision requirements, and design optimally tolerance distribution based on Monte Carlo simulation, take a example of brake assembly to detailed introduce the use of this method. The purpose of this article is expected to make the following contributions: (i) to help the designers to evaluate products for assimilability, (ii) to provide a new perspective to tolerance problems, and (iii) to provide a tolerance analysis tool, VisVSA, which can be incorporated into a CAD or solid modeling system.

Tolerance Optimal Design System Development and Application Based on UG Quick Stack Module

Computer-aided design tolerances (CADT) technology got far behind the CAD, CAPP, CAM etc, although there are many commercial tolerance software, but the tolerance optimal design still can’t be completed, which seriously affects the CAX technology's integral roles. Based on the tolerance computation function of the UG Quick Stack module, this paper accomplishes the product assembly relation modeling, tolerance distribution, locked circle calculation and so on, achieves the optimal design tolerance of whole product.

Advances in and Limitations of Up-and-down Methodology

Sequential design methods for binary response variables exist for determination of the concentration or dose associated with the 50% point along the dose–response curve; the up-and-down method of Dixon and Mood is now commonly used in anesthesia research. There have been important developments in statistical methods that (1) allow the design of experiments for the measurement of the response at any point (quantile) along the dose–response curve, (2) demonstrate the risk of certain statistical methods commonly used in literature reports, (3) allow the estimation of the concentration or dose—the target dose—associated with the chosen quantile without the assumption of the symmetry of the tolerance distribution, and (4) set bounds on the probability of response at this target dose. This article details these developments, briefly surveys current use of the up-and-down method in anesthesia research, reanalyzes published reports using the up-and-down method for the study of the epidural relief of pain during labor, and discusses appropriate inferences from up-and-down method studies.