Abstract

Assembly line balance

The results show that the algorithm improves upon the best-performing methods from the literature in terms of solution quality,and verifies more optimal solutions than the other available exact methods

Introduction

Tolerance Design

Begin

1. The design of the entire manufacturing process of a product –and more particularly the assembly process – has a key impact on the performance of an industrial company.

2. Manufacturing imprecisions and measurement uncertainties lead to observable geometric deviations, which decrease the function and quality of mechanical products and have thus to be limited by geometric tolerances.

3. The objective of tolerance analysis is to check the feasibility and quality of assemblies or parts for a given GD&T scheme.

4. Manufacturing tolerances serve to satisfy not only the functional requirements given in the product definition model, but also the manufacturing constraints, such as machine accuracy and minimum extra machining thickness.

Content

1. The application of GDT for mechanical design has gained widespread acceptance in industry.

2. Geometrical tolerancing allows the designers to specify the maximum available tolerance and consequently (从而) design the most economical parts.

3. A properly tolerance drawing is not only a picture that communicates the size and shape of the part, but it also explains the tolerance relationships between features.

4. In this paper, angularity is taken for study.

5. As shown in Fig. 1.

6. Tolerance stack ups of individual components and their assembly have been carried out (开展) using graphical approach.

7. Many efforts have been made to develop assisting solution for assembly process planning.

8. Several methods have been proposed in (提出) the literature to evaluate (direct problem) or to optimize (inverse problem) assembly process plans.

9. But these methods are generally limited to a single aspect of the general problem – such as sequence planning or tolerancing – and a single performance indicator.

10. This paper aims at proposing an original method to select assembly techniques and to allocate geometrical tolerances on components by solving a multi-objective optimization problem to minimize cost and maximize quality.

11. Extensive (大量的) work has been conducted (进行) to assist the generation of assembly sequences.

12. However, very few issues about assembly technique selection are addressed.(得到解决)

13. The aim of this paper is to propose a method to select an assembly technique for each joint of a product and to allocate geometrical tolerances accordingly.

14. Research works assert (断言) that the tolerance stack-up has an impact on the F.E results[1] and the assembly process[2] as the case of the sheet metal assembly[3].

15. In our previous work, a method taking into account the tolerances on (考虑) CAD model was established [4] (已发表).

16. In the past, various mathematical approaches for the representation of geometric tolerances in tolerance simulation models have been proposed.

17. The objective of tolerance analysis is to check the feasibility and quality of assemblies or parts for a given GD&T scheme.

18. A large amount of fundamental research efforts has been given to explore the mathematical basis for tolerance analysis.

19. It is very important to avoid warranty returns and manage the rate of out-of-tolerance products in production that can lead to assembly line stoppages and/or wastage of out-of-tolerance mechanisms.

20. The approach proposed here focuses on adjusting the dimensions of the inner components rather than trying to reduce the impact of the sources of variation.

21. This model fills a research gap (填补了研究空白) as it holds a relational focus on how actors, tools, and communication flow in collaborative design between the different main activities in PD.

22. When it comes to (当涉及到) mechanical structures composed of a high number of components, like aeronautical structures, choices made for the assembly process account for a large share in the total delivery cost and geometrical quality of the assembled products.

23. Manufacturing imprecisions and measurement uncertainties lead to (导致) observable geometric deviations, which decrease the function and quality of mechanical products and have thus to be limited by geometric tolerances.

24. Various numerical methods were employed to (被用来) deal with complicated computations associated with tolerance design models.

25. A substantial amount of research has been carried out regarding optimal tolerance allocation using cost- -tolerance functions.

26. Despite numerous studies have been conducted in tolerancing during the last decades and many scientific progresses have been achieved, the problem is still far from solved, typically regarding three-dimensional manufacturing tolerancing.(用于总结的开始)

27. Making trades-off (作权衡) between automated and manual assembly plans proved to be very complex.

Introduction conclude

1. The second section details the data structure used to define a parametric assembly plan, what is required to tackle its optimization. The multi-objective optimization set to solve the problem addressed in this paper is described in the third section.

2. The entire method is illustrated through a simple case study presented in Section 6 where results are exposed and discussed. It is followed by a conclusion.

FSW

This paper study on the difference effect of tool forces cause by different tool pin. The threaded cylindrical pin is best for FSW.

Most of the literature on FSW focuses on aluminum alloys; however, recently interest has grown in applying this technique to the joining of thermoplastic materials.

This paper addresses this gap (弥补差距) of a study on the effects of process parameters.

In the paper a new fixture for FSW of Ti-alloys was proposed(建议) and the results of experiments were presented.

In the recent years few attempts were carried out(开展) to develop FSW process aimed to maximize the mechanical performances of the welded parts.

Bakavos and Prangnell (2009) investigated the effect of pin length on the lap shear strength of FSSW welds produced in a 0.91 mm aluminum sheet.

Bakavos et al. (2011) first demonstrated (展示) the material flow was strongly influenced by surface features of the shoulder.

Tozaki et al. (2010) also performed (完成)FSSW using the scroll tool, and showed that it can produce high strength welds in a 2 mm thick sheet, although a depth of penetration greater than 0.5 mm was required.

The strength of welds in FSSW is mainly influenced by material flow and heat generation between the tool/workpiece interfaces, as reported by Mishra and Ma (2005).

Chao and Qi (1998) established a method to estimate heat generation.

It has also been shown in Bhushan (1999) that the friction coefficient of Al on mild steel is in the range of 0.5–0.6, but the friction coefficient of Al self-mated pair is in the range of 0.8–1.2.

The analysis was conducted on (实施了) the welded surfaces instead of the section (Zucchi et al., 2001) taking into account that the surface is the part more exposed to the environment.

In recent years, the application of FSW has been a research focus.

Despite(尽管) the widespread growth of FSW as a commercial joining process, the development and evolution of the microstructure at welded joint, the relationship between microstructure and properties of joint is not well understood.

FSW is a solid-state welding process that has been proven to be very effective for joining of some metallic materials such as aluminums, copper, and magnesium alloys.

In contrast to fusion welding techniques, FSW results in a much lower distortion, no welding arc, a lower weld finishing costs, and the lower residual stresses associated with a low heat input of the processing.

While the research and applications of FSW have mainly focused on the aluminum alloys, investigations into the FSW of copper and copper alloys are quite limited.

They reported the grain size of the stirred zone (SZ) decreased from 9 to 3.5 lm with decreasing rotation rate from 800 to 400 rpm at constant traverse speed of 50 mm/min.

They indicated that variations of both micro hardness and yield strength of the SZ are related to grain size with the Hall–Petch relationship.

Alternatively, Aota and Ikeuchi (2010) performed FSSW using a dome-shaped tool without a pin, and reported that the depth of the material flow was less than 0.5mm.

A number of studies have been conducted to evaluate the feasibility of FSW of magnesium alloys.

One concern with this reasoning is that, in such series of welds it is not only the tool rpm that is varied

In the published literature the effects of forge force have not received as much attention as tool rotation and welding speed effects.

At about same time Record et al. reported a design of experiment based approach where nine welding parameters were used.

As the application of friction stir welding widens it will be important to understand the behavior of process variables.

This understanding will be helpful in a variety of scenarios.

Bautista et al. (2010) stated that the intrinsic electrical conductivity also depends significantly on the mechanical strain.

Hardness measurements are usually performed to evaluate the hardness field of a joint, directly correlated with the microstructure produced during Friction Stir Welding (FSW) as shown by Barcellona et al. (2006).

In aluminum alloys a large variety of second phases and precipitates is observed depending on the chemical composition of major alloying elements and the time to form complete or incomplete stoichiometric precipitates (Mishra and Ma, 2005).

Lakshminarayanan and Balasubramanian (2008) quantified (量化) the contribution on UTS of rotational speed, feed rate and axial force on welded specimens of a ZnMgAl alloy, applying the statistical Taguchi method for process parameters optimization.

Ericsson and Sandstrom (2003) emphasized (强调) the relevance of fatigue behavior of FSW joints for aircraft and automotive appli-cations.

In the last few years many efforts were carried out to investigate the fatigue properties of friction stir welded joints and how they can be related with welding process.

James et al. (2003) deeply analyzed the influences of process parameters, welding defects and residual stress on the fatigue behavior.

Shusheng et al. (2006) referred (提到) a ‘zigzag-curve’ defects that can occur over the whole section of the stir zone, even if optimized welding parameters are employed.

Cirello et al. (2006) examined the influence of relevant FSW process parameters, i.e. the tool rotating speed, the feed rate and the tool sinking into the samples, on the fatigue resistance of AA6082-T6 butt joints.

Feng et al. (2010) observed the effects of the welding parameters on the LCF behavior and microstructure evolution of friction stir welded 6061Al-T651 alloy.

The influence of FSW on the fatigue life of Al6063-T6 notched samples was investigated in Moreira et al. (2008).

In the present work, an analytical model for heat generation for taper cylindrical (TC) pin profile in FSW was developed.

Khandkar et al. introduced a torque based heat input model for SC pin profile.

Gadakh and Kumar have made an attempt to develop an analytical model for heat generation for TC pin profile but they have modeled it incorrectly.

Suresha et al. reveals (揭示) that the conical tools show better joint efficiency compared to the square tools.

According to Liu and Zhang, for a fusion welding process model, the welding distortion decreases with increasing restraining force.

FSP has been successfully employed in several aluminum alloys to confer or enhance superplasticity.

Main Contain

Tolerance Allocation

About Pic, Table and Equation

1. The inverse problem displayed in Fig.1 is solved thanks to a multi-objective optimization.

2. In order to provide a clear representation of the sequence, both approaches are combined in an Assembly Sequence Graph. An example is displayed in Fig. 3.

3. Table 1 gives an example of an assembly technique to make a temporary joint between a tool and a component.

4. Fig. 5 presents an overall flowchart of the search for non-dominated points in the non-conformity rate versus cost plane.

5. The difference between these two problems is illustrated in Fig. 3. In tolerance analysis the component tolerances are all known or specified and the resulting assembly variation is calculated. In tolerance allocation, on the other hand, the assembly tolerance is known from design requirements, whereas the magnitude of the component tolerances to meet these requirements are unknown.

Content

1. A tolerance has to be allocated to each component dimension to ensure that the product’s KC are kept within the authorized boundaries.

2. The manufacturing company know-how can be formalized by building an assembly technique library.

3. When it comes to assembly technique selection, not only the recurring cost has to be taken into account, the non-recurring cost must also be evaluated.

Instance

Tolerance Allocation

1. In order to illustrate the proposed method, a rod and crankshaft assembly (Fig. 14) is selected as a validation (验证).

2. A prismatic part to be machined is used to illustrate the proposed approach, as shown in Fig. 2.

3. The models and method mentioned above can be verified by taking a precision horizontal machining center for an example.

Conclusion

Tolerance Allocation

Lead

1. The present paper explains an efficient and effective graphical method that aims towards the systematic solution of tolerance stack up problems.(1st)

2. Based on the results of analysis, reallocation of tolerances can be done to fulfil the functionality of the system.

3. This paper aims at presenting an original method for computer-aided assembly process planning. (1st)

4. This paper has presented comprehensive and systematic mathematical tools for dealing with the tolerance analysis and synthesis of cam-modulated linkages.(1st)

Undertake

1. It addresses the problem of assembly technique selection and of component geometrical tolerance allocation.

2. This problem is solved to satisfy both objectives of minimizing a cost indicator and maximizing a quality indicator.

3. This is achieved by writing a multi-objective optimization problem.

文章针对——问题所在——问题描述——如何实现

Details

1. The objective of this optimization model is to maximize the manufacturability and assembility of a cam-modulated linkage while maintaining acceptable kinematic accuracy of its output motion.

2. As opposed to some others methods in the literature, tolerances are design taking into account the singular value decomposition of the dependence structure of data.

3. To verify the fitting quality of parts in a mechanical assembly, a new criterion called the assemblability index is introduced.

Ending and instance

1. Therefore, the proposed approach is well adapted to (非常适合于) an industrial context (工业背景下) where decision-aid capabilities are essential. 用于总结方法

2. The use case and the quality and cost indicators presented in this paper are intentionally kept simple to let the reader focus on the global method.

3. More complex models for non-conformity rate or cost evaluation can easily be applied using the same framework.

The method is currently under test on industrial-scaled use cases.