Fixture Assembly Research Articles

Design, simulation and experimental investigation of a novel reconfigurable assembly fixture for press brakes

A reconfigurable assembly fixture is a major and important component of a reconfigurable assembly system. It is required for the assembly of a variety of press brake models in order to reduce the assembly time and overall production time. The stages and requirements for the design of an assembly fixture and understanding of the assembly process for press brake models were used to design a reconfigurable assembly fixture. A detailed design analysis of parts of the fixture and the hydraulic system is considered and presented in this article. The stress and displacement analysis of the parts is executed using Solidworks express simulation. The parameters of the hydraulic components were determined from force requirements, and the hydraulic system was modelled physically using Matlab Simscape hydraulics. The response of the hydraulic system was obtained for each actuator in the system in order to depict the output of the actuators from the spool displacement of the valves. Stress analysis conducted on parts of the fixture showed that it can withstand maximum stresses that are lesser than the yield strength of the material used for the part. It was also established that synchronization of hydraulic actuators can best be achieved by the use of a sine input to the electrohydraulic valve. An experimental investigation was done using FESTO hydraulic test bench in order to observe the synchronized extension and retraction of the hydraulic actuators. The simulation of the hydraulic system, electric system and the programmable logic controller was prepared using automation studio. The design is envisaged to provide the industries with relevant information on accurate location and gripping of press brake frames rather than turning and repositioning of the frame in order to fit other parts during assembly. The article provides relevant information on the design analysis of a reconfigurable assembly fixture for press brakes which is novel because articles on reconfigurable assembly fixtures have not considered its application to press brake assembly.

English

English

Aircraft Part and Its Assembly Fixture Model Based on Multi-domain Integrated Mapping

Aircraft Part and Its Assembly Fixture Model Based on Multi-domain Integrated Mapping

Variation simulation of stress during assembly of composite parts

Weight reduction requirements in aerospace and automotive industry lead to an increased use of composite materials. However, composite parts cannot be bent like sheet metal parts. Hence, only low forces can be applied to close gaps between parts, caused by geometrical variation in parts and assembly fixtures. Shimming is therefore used to compensate for bad fitting, with increase cost as a consequence. This paper investigates how variation in assembly fixtures and parts give rise to variation in gaps and thereby also to variation in stress. Monte Carlo simulations are used to find the distribution of stress, which supports shimming strategies.

Fixture Design Optimisation Considering Production Batch of Compliant Non-Ideal Sheet Metal Parts

Fixtures control the position and orientation of parts in an assembly process and thus significantly contribute to process capability that determines production yield and product quality. As a result, a number of approaches were developed to optimise a single- and multi-fixture assembly system with rigid (3-2-1 fixture layout) to deformable parts (N-2-1 fixture layout). These approaches aim at fixture layout optimisation of single ideal parts (as define by CAD model). However, as production yield and product quality are determined based on a production volume of real (non-ideal) parts. Thus, major challenges involving the design of a fixture layout for assembly of sheet metal parts can be enumerated into three categories: (1) non-ideal part consideration to emulate real part; (2) ‘N-2-1’ locating scheme due to compliant nature of sheet metal parts; and, (3) batch of non-ideal parts to consider the production process error at design stage.This paper presents a new approach to improve the probability of joining feasibility index by determining an N-2-1 fixture layout optimised for a production batch of non-ideal sheet metal parts. The proposed methodology is based on: (i) generation of composite parts to model shape variation within given production batch; (ii) selection of composite assembly representing production batch; (iii) parameterisation of fixture locators; and (iv) calculation of analytical surrogate model linking composite assembly model and fixture locators to probability of joining feasibility index. The analytical surrogate model is, then, utilised to maximise the probability of joining feasibility index starting from initial fixture locator layout. An industrial case study involving assembly process of remote laser welded door assembly illustrates and validates the proposed methodology.

2P1-W06 掌にカメラを装着した4指12自由度ハンドによる治具組立の基礎研究

Due to introducing robots to industrial production lines, it is expected that the productivity is increased, labor costs are reduced, and regular production is kept. At present, however, dexterity embedded into the robots is much inferior to skills of human beings. To improve the dexterity, we investigate robotic assembly of fixtures used in the production lines. To assemble the fixtures, we use a 4-finger 12 d.o.f. hand with a camera on the palm. In this paper, we investigate a grasp and insertion task of a bolt to a hole. And we investigate a grasp and insertion task of a slide unit to another slide unit. In these tasks, uncertainty of grasping by the hand occurs. To overcome the problem, we utilize the information of a 6-axis force sensor equipped in the robot wrist and the camera image.

Wax Patterns for Integrally Cast Rotors/Stators of Aeroengine Gas Turbines

Modern turbine engines for aerospace applications need precision investment cast components such as integrally cast rotors and stators, for their hot end turbine stages. Traditionally, these turbines are used as starter engines. In recent times, such engines are also used for strategic missile applications. The rotor/stator castings consist of a central hub (shrouded in some designs) over which a number of aerofoil shaped blades are located. Since these components cannot be machined, investment casting is the only available route for manufacture and hence stringent dimensional aerospace quality has to be in-built in the casting process itself. In the process of investment casting, pattern generation by injection of wax into dedicated dies/moulds is the first critical step. Traditional approach deals in producing individual blades with hub/shroud features through wax injection and assembly of a set of such injected patterns onto a dedicated and precisely manufactured fixture to wax-weld and generate an integral wax pattern, a process known as the ‘segmental approach’. It is possible to design a single-injection die with retractable metallic inserts in the case of untwisted blades of stator patterns without the shroud. Such an approach is also possible for twisted blades of rotors with highly complex design of inter-blade inserts and retraction mechanisms. DMRL has for long established methods and procedures for the above to successfully supply precision castings for various defence related projects. In recent times, urea based soluble insert approach has also been successfully applied to overcome the need to design and manufacture a precision assembly fixture, leading to substantial reduction in component development times. Present paper deals in length various approaches tried and established at DMRL to generate precision wax patterns for aerospace quality turbine rotors and stators. In addition to this, the importance of simulation in solving issues related to wax injection is also touched upon.

Application of Virtual Reality Means in Dashboard Function and Dashboard Assembly Fixture Ergonomic Analysis

Manual assembly has in some areas of production dominant role. For its effective performance the different jigs and fixtures may be used. For the design of such fixtures, it is useful to use CAD systems. The proposed fixture is necessary to additionally verify from the different points of view, including the ergonomic. For the fixture verification from ergonomic point of view, it appears that it is useful to use virtual reality components such as data gloves and their connection to the CAD design. The article describes the application of data glove for the verification of the functionality of the product and the functionality of its assembly fixture from ergonomics point of view.

AN AUTOMATIC FIXTURE DESIGN SYSTEM FOR CREATING PRISMATIC PARTS

A modular fixture system is a flexible alternative to a dedicated fixture. In this paper, an automatic modular fixture design system is suggested for creating prismatic parts. The system contains fixture planning, fixture modelling, and fixture assembly. The part geometrical database and process plans are considered as inputs to the system. A rule- based method is applied to assign the feasible locating scheme and the locating and clamping datum. The search strategy is designed to determine the most suitable locating and clamping points. The final fixture assembly is made with the standard fixture components using the CATVBA Editor inside CATIAV5. The proposed methodology is successfully validated with a case study.

Design and analysis of an assembly fixture for the column of a CNC horizontal machining centre

Design and analysis of an assembly fixture for the column of a CNC horizontal machining centre

An automatic fixture modeling system using search strategy

Fixtures are critical part of both traditional and modern manufacturing operations. The time allocated to the design and manufacture of these components significantly impacts production cycle time and can improve the quality of current and future products, and therefore, significant consideration is required to design fixture and their applications in manufacturing. In this article, design of an automatic modular fixture modeling system is proposed for prismatic components. The proposed system consists of fixture planning, fixture layout, and fixture assembly modules. The process and setup plans are used as input into the system. A rule-based system is developed to assign suitable locating scheme to locate and clamp datum for fixture planning phase. The search strategy is designed to select the locating and clamping points based on geometric and functional constraints. The final fixture assembly is achieved using standard fixture components and CATVBA editor using CATIA V5 as the platform. The graphical fixture database is constructed using commercial fixture components from manufacturers such as Fixture Works and Carrlane. The proposed methodology is successfully validated with multiple case studies.

Review of the application of flexible, measurement-assisted assembly technology in aircraft manufacturing

Aircraft assembly is the most important part of aircraft manufacturing. A large number of assembly fixtures must be used to ensure the assembly accuracy in the aircraft assembly process. Traditional fixed assembly fixture could not satisfy the change of the aircraft types, so the digital flexible assembly fixture was developed and was gradually applied in the aircraft assembly. Digital flexible assembly technology has also become one of the research directions in the field of aircraft manufacturing. The aircraft flexible assembly can be divided into three assembly stages that include component-level flexible assembly, large component-level flexible assembly, and large components alignment and joining. This article introduces the architecture of flexible assembly systems and the principles of three types of flexible assembly fixtures. The key technologies of the digital flexible assembly are also discussed. The digital metrology system provides the basis for the accurate digital flexible assembly. Aircraft flexible assembly systems mainly use laser tracking metrology systems and indoor Global Positioning System metrology systems. With the development of flexible assembly technology, the digital flexible assembly system will be widely used in current aircraft manufacturing.

Study on Surface Electric Field Simulation of High Voltage Transmission Line Assembly

For the studies in the field of high voltage power transmission, this paper has adopted the method of finite element node potential, and put forward two kinds of high pressure sensor-fixture modeling scheme for the sensor-fixture of the high voltage side, the simulation analysis shows that the sensor-fixture surface should be smooth, and should not appear the conclusion of edges and corners. While through establishing the four clamps assembly optimized model, and simulates the strain gages, fixtures and conductor surface field strength and electric field distribution in the model as a whole in turn, this paper Finally got the optimal size of fixture structure and assembly of each part reasonable location layout.

Comparison of Weighted Decision Matrix, and Analytical Hierarchy Process for CAD Design of Reconfigurable Assembly Fixture

Reconfigurable assembly fixtures are major components of a reconfigurable assembly system. They are precision components which require an intensive design process due to their usage and interaction with other components in the assembly system. Concept selection is a time consuming activity in the engineering design process, because it involves decision making and consideration of multiple factors. A computer aided design approach of four concepts was developed for a reconfigurable assembly fixture, based on functional requirements, cost, and manufacturability. The weighted decision matrix and analytical hierarchy process was used to compare these concepts. The decision criteria and evaluation technique used during this concept selection process is novel thus calling for its application in design of engineering components. The results of the two methods are presented graphically and the variations in the results obtained are used to judge the suitable method among both processes for the optimal design.

Production scheduling of assembly fixtures in the aeronautical industry

In this work, we study the production scheduling of a real world assembly problem present in the aeronautical industry. Parts of aircrafts should be produced on fixtures, which are commonly used in aircraft manufacturing and consist of several workstations. Due to a lack of physical space in the fixture, when a workstation is in use, other workers cannot use adjacent workstations in this fixture. These constraints are called here adjacency constraints. This assembly fixture scheduling problem is studied in the context of a workforce learning process including four main qualification stages (or epochs). Mathematical models are developed and implemented for each stage using a modeling language and an optimization solver. Computational experiments with this approach were performed in a case study of a Brazilian aeronautical company and they resulted in better solutions than those currently practiced in the company.

Otimização na programação de montagens na indústria aeronáutica

Este trabalho estuda um caso prático de programação da produção na indústria aeronáutica. Tarefas devem ser programadas em gabaritos de montagem com várias estações de trabalho adjacentes entre si, levando em consideração restrições especiais de processamento simultâneo destas tarefas (restrições de adjacência). Tais restrições surgem devido às limitações de espaço físico no gabarito. Este estudo é uma continuação do estudo anterior publicado em Silva, Morabito e Yanasse (2011), em que este problema foi inicialmente abordado do ponto de vista de minimizar o makespan para processar todas as tarefas. Aqui o problema é visto de forma mais abrangente no contexto de qualificação de força de trabalho com quatro fases, em que o objetivo é minimizar as necessidades de mão de obra para executar a programação em cada fase, sendo que cada fase de qualificação é representada por um modelo de otimização linear inteira. Estes modelos foram implementados em um software de otimização e vários experimentos computacionais foram realizados para verificar a aplicação da abordagem. Os resultados sugerem que existem ganhos de produtividade importantes que podem ser explorados utilizando os modelos desenvolvidos neste trabalho.

An intelligent interactive approach for assembly process planning based on hierarchical classification of parts

Assembly process planning is a difficult problem in the product design and development process. In order to reduce the difficulty of assembly process planning (APP), this paper presents an approach to finding a practical plan for assembly process through the intelligent interactive method based on hierarchical classification of parts. First, two hierarchical classification principles towards interactive disassembly are presented based on the key assembly constraint (KAC). Then, the initial assembly relationship of the product is readjusted to a new hierarchical structure which is more suitable for assembly planning according to a novel hierarchical classification algorithm. On the basis of the new hierarchy of product, an intelligent disassembly-based approach is presented, which not only takes full advantage of the ant colony algorithm for searching and constructing an initial assembly sequence with three available assembly principles, but also makes full use of the experience and knowledge of the human being for achieving a better assembly process. The intelligent disassembly approach can achieve an optimized assembly sequence, paths and scheme necessary information regarding the required assembly fixtures and tools. Finally, a case study shows that the proposed approach is feasible and practical.

Finite Element Analysis for Assembly Fixtures Based on ANSYS

Structure analysis is a vital link while designing aircraft assembly fixtures. ANSYS software is applied to analyze the structure of an aircraft assembly fixture based on a general method proposed in this paper. Firstly, a frame-type riveting assembly fixture is modeled, the static load and the boundary condition is preset according to the requirement of finite element analysis. Secondly, the static stiffness and strength is calculated considered both the condition with and without working load. Finally, the analysis and optimization process is conducted. The effectiveness and feasibility of this method has been proved combined with the simulation result and the reality test. The method can be applied to other aircraft assembly fixture when taking finite element analysis, thus it has the application and popularization value.

Application of the Jacobian–torsor theory into error propagation analysis for machining processes

The Jacobian–torsor theory is used to provide mathematical models of tolerance analysis, establishing a mathematical relationship between the open loop and closed loop of tolerances. The model allows additional chain of torsors joining them. So it is easy to model new ones. Therefore, the ability to calculate the end tolerance of assembly is useful in error propagation analysis. This paper formulates the error propagation model based on the Jacobian–torsor theory. With this theory, workpiece, fixtures, machine tool, and tool are regarded as an assembly. As a result, error sources can be grouped in a sequential manner and described by the parameters of the small displacement torsor. Moreover, the corresponding error propagation model can consider nonpunctual contacts of the fixture assembly, overcoming the limitation of the 3-2-1 layout. An experiment was conducted to demonstrate the model application and verify the effectiveness of the proposed methodology.

A constraint-based tolerance analysis in a multi-operation single setup and multi-operation multi-setup part–fixture assembly

This paper presents a constraint-based approach to tolerance analysis in a multi-operation single setup and multi-operation multi-setup part–fixture assembly. First, several error sources are identified, modeled individually, and combined into a single accumulated error model that contribute to the final accumulated tolerances. This is used to determine the position and orientation of a machined feature. Second, the accumulated errors are expressed a function of the deviation parameters of the small displacement torsor (SDT). Third, a relationship is established between the tolerance requirements and the SDT parameters using a constraint-based mapping. The constraints capture the essential property of the part accuracy requirements and serve as boundaries for the machined feature. The method has the following advantages: (a) it establishes a direct link between error sources and part accuracy requirements, (b) it provides a direct way of evaluating the effect of each error source as well as their combined effect on part accuracy, and (c) it serves as a feedback system with the capability of providing advanced knowledge of the various physical behaviors of the part-to-fixture elements. Two simple examples are used to illustrate the approach.