基于小位移旋量公差建模和蒙特卡洛模拟的装配体公差优化设计方法

提出一种基于小位移旋量(SDT)公差建模和蒙特卡洛模拟的装配体公差优化设计方法,通过分析装配精度链、装配结合面和结合面公差3个对装配精度具有重要影响的核心要素之间的关系,利用SDT理论和蒙特卡洛模拟法建立公差模型,再利用齐次变换理论建立结合面误差模型和装配精度模型,进而推导出装配体装配精度与结合面公差相关的映射模型;结合公差制造成本、装配精度可靠度原则,建立装配体装配精度的公差优化模型,并以顶尖装配体为例完成公差优化分析。研究发现:在满足装配精度可靠度的前提下,可使顶尖装配体加工成本降低9.02%,而装配精度可靠度提高至97.81%,验证了所提方法的有效性。     

Creo产品装配成功率预测系统开发

为了解决在产品设计阶段对产品装配精度与装配成功率进行预测的问题,针对装配体模型,基于公差分析理论,运用VS2010与Matlab混合编程技术,开发了Creo环境下的装配成功率预测系统。该系统可以对装配体约束信息、材料特征、形状特征、精度信息(包括尺寸精度、几何精度、表面精度)等进行自动提取,基于极值法、概率法和蒙特卡罗法等对装配体进行公差分析,基于蒙特卡罗法进行装配体模型装配精度的自动计算和装配成功率预测,最后以某齿轮装配件为研究对象对系统进行了测试应用。结果表明,该系统可以便捷、准确地实现产品装配成功率的预测。     

飞机薄壁零件装配偏差建模与仿真分析

为了准确有效地实现飞机薄壁零件装配偏差预测与控制,提出一种飞机薄壁零件装配偏差建模与仿真分析方法。根据飞机薄壁零件装配工艺过程,考虑零件制造偏差、工装夹具偏差和装配变形,基于确定性定位法和影响系数法建立装配偏差模型。在此基础上,基于蒙特卡洛法对装配偏差模型进行仿真求解,根据偏差源敏感度进行装配偏差优化。以某型飞机机身壁板装配偏差分析为例,验证了所提方法的有效性。     

A computer aided chaining approach for predicting the shape accuracy in manufacture of automotive structures

The increasing competition and the urge to reduce costs and shorten product-life-cycles in the automotive industries imply the application of virtual manufacturing mock-ups. Computer aided engineering methods including simulations of the structural behavior during manufacturing and assembly contribute to eliminate trial-and-error along the production chains of vehicle structures. Such digital mock-ups also provide an input for additional tolerance analyses and allow the identification of the pending quality of structure components in advance. In this way large numbers of experiments and adjustments on the existent production lines can be avoided. In this paper an approach is introduced, which allows the replication of the physical effects along manufacturing chains based on thermo-mechanical models. The rendered results after considering successive operational steps provide the basis for initial estimations regarding the shape accuracy of structure assemblies. For a specific example of the automotive body-in-white a first run of a manufacturing process chain is investigated in order to predict the shape quality of a probable production cycle by applying a tolerance chain analysis. The results enable the scrap identification due to non-satisfied quality of assemblies. Finally, based on the achieved results a re-engineering of the manufacturing chain is suggested in order to fulfill quality requirements.     

拆解机工作装置运动学分析与仿真

以拆解机为研究对象,利用D-H方法对拆解机工作装置进行运动学数学建模,获得相应的正向运动学方程,结合蒙特卡罗法在MATLAB中进行仿真,得到拆解机工作空间模拟图,明确运动过程中的极限位置及其与拆解机各部件尺寸的关系。建立拆解机工作装置虚拟样机模型,利用ADAMS软件对结构进行运动仿真,得到工作装置运动过程中的空间轨迹仿真曲线。与MATLAB中的工作空间模拟图进行对比后可知,两者基本一致。分析结果表明:应用D-H坐标系及蒙特卡罗法对拆解机进行运动学分析和仿真,能够在得到的结果具有一定正确性的同时提高设计效率,为拆解机实际应用提供参考。     

Allocation of assembly tolerances to minimize costs

The cost and quality of an assembly depend on the processes used to manufacture its components. The specific processes and process settings are often dictated by the tolerances on the components. One long-standing challenge is allocating the assembly tolerance to components. Many methods have been proposed, most of which endeavor to minimize cost. We propose a tolerance allocation method that minimizes cost by jointly considering process variation and tolerance specifications. A cost model including processing cost, scrap cost, and quality loss is employed. The cost is minimized by a heuristic strategy. An overrunning clutch assembly case study is used to evaluate the method.     

An accuracy analysis of the peg-and-hole assembly problem

A peg-and-hole assembly may adopt clearance, transition or interference fits depending on the functional requirements of the particular design. The international standards that are used for the specification of the nature of a fit refer, nevertheless, only to dimensional deviations. They do not consider the actual geometry of the assembly components. Geometrical tolerances are assigned in addition to the dimensional tolerances whereas, for certain applications, the latter may also include some provision for them. Maximum and minimum functional clearances, dimensional and geometrical tolerances of a peg-and-hole assembly consist of a system where values of the first two variables are design-imposed and the dimensional/geometrical tolerance values have to be suitably allocated. This tolerance allocation cannot, however, be effected by a straightforward approach. The unknown variables are more than the available clearance/tolerance relationships and in the current engineering practice, the problem solution is usually based on experimental/empirical data and/or general tolerance assignment guidelines. The paper addresses this problem through a systematic analysis of the accuracy requirements of a peg-and-hole clearance fit assembly. The analysis is then followed by the development of a methodology for the evaluation of the dimensional and geometrical tolerances of the assembly components. The presented algorithm is further applied and discussed in a case study.     

基于3 DOF并联机器人的误差分析

目前使用比较广泛的公差分析方法是通过装配尺寸链得到公差设计函数,但该方法不能有效适用于结构复杂且精度要求极高的机器人制造业。基于仅考虑主动关节误差的情况下,通过误差数学模型的建立,对定向误差以及位置误差进行分析,进而得到三自由度并联机器人的结构的详细分析结果,并提供了基于数值分析方法在给定标称配置下计算机器人定向误差和位置误差的有效方法。     

Modeling and Control of Compliant Assembly Systems

The assembly of compliant, non-rigid parts is widely used in automotive, aerospace, electronics, and appliance manufacturing. Dimensional variation is one important measure of quality in such assembly. This paper presents models for analyzing the propagation of dimensional variation in multi-stage compliant assembly systems and the use of such models for robust design and adaptive control of assembly quality. The models combine engineering structure analysis with advanced statistical methods in considering the effect part variation, tooling variation, as well as part deformation due to clamping, joining and springback. The new adaptive control algorithm makes use of the fine adjustment capabilities in new programmable tooling in achieving reduction of assembly variation.     

一种基于关键特性识别的综合成本公差优化模型

当前基于制造成本与质量损失的公差优化模型缺乏对制造成本与产品质量间复杂关系的考虑以及对关键特性的控制。针对这一问题,提出一种引入制造成本与质量损失的权重系数和组成环灵敏度系数的装配公差优化模型。该模型的权重系数由设计、工艺、制造以及市场调研等相关领域专家进行评判打分确定,灵敏度系数依据关键特性识别的数学模型获取。最后以某型飞机外襟翼接头为例,验证该模型的可行性和有效性。     

浅淡汽车门槛加强板的工艺分析与优化

以某车型门槛加强板为例结合装车匹配过程中易出现匹配间隙大的问题,从工艺设计、模具设计及制件变更等方面找到一些好的方法来解决优化门槛加强板易出现的回弹问题,从而缩短了开发周期,降低了调试成本,改善制件质量。     

Technology chain optimization: a systematic approach considering the manufacturing history

The optimization of technology chains is usually conducted as a local problem of each individual process step. However, in order to optimize the technology chain in terms of product properties a local optimization is insufficient and a more holistic approach is indispensable. Existing methods, which consider the manufacturing history of a workpiece, are often accompanied by a high level of effort in research. This paper presents a systematic approach to integrate the manufacturing history into the technology chain optimization process going along with a significant reduction of effort compared to existing methods based on simulation and experiments. Resulting from previous methods and models a set of representative variables is identified to describe interactions and dependencies within technology chains. Furthermore, an approach consisting of three steps is developed which allows a visualization as well as an explanation of the cause-and-effect relationships within technology chains. This approach is used to deduce two different optimization strategies for technology chains. The first strategy allows a global optimization by adjusting specified parameters without changing the processes within the technology chain. Whereas the second strategy comprises a redesign of the whole chain.     

Wavelets-based method for variation analysis of non-rigid assemblies

This paper proposes a new method based on wavelets analysis and finite element method (FEM) for the variation analysis of non-rigid assemblies. It is well known that the part fabrication variation, coupled with the part's deformation during the assembly process, is one of the main factors affecting the assembly quality. But little investigation has been done on how component variations with different scales contribute to the final dimensional variation of non-rigid assemblies. The proposed approach takes the part variation as a signal and applies wavelets transform to decompose it into different scale components. The deformation of non-rigid assemblies that corresponds to these different scale components is calculated by using FEM. Since the part variation is resulted from manufacturing, manufacturing engineers can apply this method to get valuable information to avoid major variation causes in manufacturing process and make a better process plan. The proposed method is illustrated through a case study on an assembly of two flat sheet metal parts.     

三轴数控机床加工精度可靠性分析

机床作为机械制造业的基础,几何误差、热误差、装配误差等都会影响数控机床的加工精度,数控机床加工精度的高低直接决定产品的生产质量。为保证数控机床对产品的加工质量,需要对数控机床的加工误差数据处理,求得数控机床加工精度可靠性,而一次二阶矩法和蒙特卡罗法是常用的可靠性分析方法。以三轴数控机床为研究对象,针对给定的误差数据,运用一次二阶矩法和蒙特卡罗法分析出数控机床加工精度可靠性。此分析对提高数控机床加工精度及保证使用寿命具有重要指导意义和参考价值。     

基于仿真分析的BT40主轴系统公差设计与优化

公差设计质量直接影响产品的性能和制造成本。为提高主轴系统公差设计的质量和效率,提出了一种基于建模仿真的公差设计与优化方法。模拟BT40主轴系统的结构和装配过程,首先在CETOL6σ软件中建立主轴系统的数字化公差模型,利用该模型分析各主要公差对系统输出精度的贡献度和敏感度。然后以类比法公差设计作为原始方案,仿真检验其设计效果。最后以公差贡献度和敏感度为依据,对原有公差设计方案进行修正及优化。结果表明:优化后的方案显著提高了主轴系统的输出精度。     

基于区间分析的平面尺寸链求解实例研究

针对极值法求解尺寸链过于保守、统计法求解尺寸链需知晓各环的概率分布等问题,研究了用区间分析方法来计算复杂平面尺寸链方程组的原理和方法。首先,将尺寸链中的各环尺寸及其偏差以区间数的形式来表示,构建区间参数方程组;其次,利用Krawczyk算子及INTLAB工具箱编写了求解区间参数方程组的应用程序,并引入区间截断法;最后,对机枪机心结构尺寸链实例分别进行了区间分析计算和CE/TOL6σ软件计算,并进行对比和分析研究。研究结果表明采用区间分析求解平面尺寸链的计算结果优于极值法,并能弥补RSS统计法的固有缺陷。     

Hosing注塑模具多功能成型零件的结构设计

分析了Hosing零件的工艺结构,介绍了分模的过程,研究并阐述在保证模具结构紧凑合理并便于修模的前提下,各成型零件的工艺结构设计及改进方法。成型零件不仅起了成型塑件形状和保证尺寸的作用,还具备了流道、导滑面、定位及支撑运动部件的功能,降低了模具的制造成本。     

Concurrent optimization of design and machining tolerances using the genetic algorithms method

The allocation of design and machining tolerances has a significant effect on both manufacturing cost and quality. This paper presents a procedure to concurrently allocate both design and machining tolerances based on optimum total machining cost. The non-linear multi-variable optimization problem formulated is solved using the genetic algorithms method. Two design examples involving concurrent allocation of both design and machining tolerances are presented to demonstrate the effectiveness of the method.     

Integrative process chain optimization using a Genetic Algorithm

For the production of forged components, it is necessary to coordinate and optimize the production stages along the process chain. This includes the mainstream processes as well as the associated process chain of the die manufacturing. Up to now, these processes and process chains are planned and optimized independent from each other because of the different and often contradictory target criteria. In this paper, a new approach for a holistic optimization of forged process chains will be presented. At first, a systematic mathematical dependency-analysis between the processes of an application scenario was carried out. Based on this analysis, a holistic Pareto-based optimization of the process parameters by the use of a Genetic Algorithm was consecutively performed. The article ends with the presentation and discussion of the computational results.     

Quantitative circularity tolerance analysis and design for 2D precision assemblies

Circular, cylindrical, or spherical features are fundamental geometric features in engineering. As precision requirement becomes more stringent, it is not sufficient to consider only size tolerance of circular and cylindrical parts. However, currently there is no quantitative and systematic way of assigning circularity and cylindricity tolerances. This paper investigates how to specify circularity tolerance quantitatively for 2D assemblies. Statistical matrices to quantify positioning error of two perfectly circular mating parts subject to size tolerance for both clearance and transition fit conditions are first developed. The analysis is then extended to nonideal profiles whose profile errors are assumed to deviate from a best-fit circle according to a normal distribution. The assumption of the normal distribution is then removed for more general results via computer simulation. For this purpose, an experimentally verified profile model is used to generate realistic profiles as those produced by various machining processes. Numerous pairs of these realistic profiles are then assembled virtually using Monte Carlo simulation to quantify their positioning errors. The simulation results and the analytical results are compared for cross-checking. Finally, systematic design procedures are proposed to assign circularity tolerance by prescribing a fit condition with a desirable process capability. By the nature of circularity tolerance, this paper addresses a 2D assembly. The result of this 2D analysis can be a foundation for more complicated 3D problems, such as assigning cylindricity tolerance.