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New design for assembly (DfA) methodology for large and heavy parts assembled on site
Abstract
A literature review on the assembly design methodologies (DfA) oriented to the assembly of large and heavy parts, reveals the need to develop a DfA methodology. In addition, the lack of DfA evaluation methods for on-site assembly is also observed. The most widespread DfA methodologies are more oriented toward the improvement of factory assembly processes, where the assembly processes are well defined and standardised. Hence, this article presents a new methodology for the design of assemblies with large and heavy parts on site, called OSIA (On-Site Installation Analysis). OSIA methodology aims to provide data (indicators). On the one hand the theoretical basis of the OSIA methodology is based on three key concepts: i) analysis of assembly operations similar to the one used by the SMED methodology; ii) generic implementation process of DfA methodologies; and, iii) compilation of assembly operation times and estimation of standard times per operation. On the other hand, the steps in the implementation of the methodology are summarized in: i) database development with assembly operations and standard times; ii) assembly operations analysis; iii) calculation of assembly time; and iv) product optimization. In this way, OSIA methodology supports the designer in the specification phase, detailed design phase and in the redesign processes, providing the designer with indicators that make it possible to optimise the design of the parts and reduce the assembly operations of a product on site.
... As mechanical assemblies are complex structures [1], their planning is challenging. Using the assembly design concept [2] one can select the best construction solution for the designed product, taking into account, i.a., the estimated standard assembly time. At an early stage of product development, data on the manufacturing process are not fully known. ...
... According to DST, the basic probability assignment (BPA) function of two pieces of evidence m1 and m2 can be calculated from the equation (2) [16]. (2) where is the fused belief degree of the two pieces of evidence; is the degree of contradictory information between B and C, referred to as a normalization factor; ...
The problem solved in this article concerns assembly planning, which is time-consuming, but crucial in the development of mechanical products. At the product design stage there is no complete information about the manufacturing process, so it is necessary to develop an approach to help process the uncertain and incomplete information. In order to compare different product variants, the assembly time standard has to be estimated on the basis of the incomplete product and production process characteristics. This paper presents a method for estimating the assembly time standard using time classes, decision tree and evidence theory.
... The DFMA approach is a technique used to assess product designs that consider how simple the manufacturing and assembly processes will be [11]. To find the value of the design efficiency index, the modification design process requires the completion of the DFA Design for Assembly (DFA) study [12]. DFA seeks to simplify products to make them easier to assemble and require less time to complete [13]. ...
The locking mechanism on the band service, known as the lock band service, is used to move materials to the tire-making machine. A building machine is a device that assembles components into partially finished or green tires. The components are tread, which acts as the tire tread, band/ply, which are fabric sheets coated in rubber, and bead wire. Subsequently, the materials are put together on the drum-mounted construction machine. The ATB-I3 machine has the largest downtime owing to a band service fault, with 840 minutes in January 2024, and is the problem with the highest downtime in section A2. The cause of the excessive downtime in the band service is an issue with the band service lock system, namely the pneumatic movement lock mechanism on the band service component. As a result, adjustments must be made by altering the lock band service's design. After that, a weld joint strength analysis is performed to make sure the modification can be safely put into practice. To obtain the optimal modification design, the DFMA method is employed. With the use of the DFMA approach, the updated design—which had a design efficiency value of 4.23% to 4.31% before—was improved. The welding connection in the updated design is safe to use since, according to the results of the welding connection calculation, the lock band service holder has a maximum welding load of 294,645.08 N whereas the actual welding load is 147,928 N. The reduction in service band downtime was tested with this improvement. Following the implementation of the update in March 2024, the amount of downtime resulting from damage to the band service dropped by 445 minutes, or 52.97%, to 395 minutes
... Due to the distinct characteristics of large-scale equipment, tailored assembly solutions are imperative to monitor errors in the assembly process effectively, thereby meeting stringent precision requirements [4][5][6]. To tackle the aforementioned assembly monitoring challenges, Liu et al. [7] propose an Intelligent Collaborative Assembly System (ICAS) that leverages a blend of data-driven methodologies and Augmented Reality (AR) technology to facilitate real-time monitoring of assembly processes for large and complex products; Pang et al. [8] proposed to utilize point cloud processing algorithms with digital twin (DT) technology to compose a physical twin scene (PT) to represent on-site assembly, and to compose a part-centered manual assembly-assisted monitoring system; Peng et al. [9] propose a remote measurement system that integrates attitude sensors and laser sensors to perform measurement tasks during docking in outdoor environments. ...
Large components are crucial in modern industrial applications, especially for internal gap monitoring and specific assembly methods. This paper examines the assembly of hydroelectric generator rotors and stators, introducing a spatial relative position monitoring system using multiple sensors. A dedicated position monitoring program is designed, and error sources within the system are thoroughly explored. Detailed error analysis and modeling reveal that verticality and angular errors significantly impact monitoring accuracy. To address this, two error control methods are proposed to effectively mitigate these issues, ensuring precise assembly of large components.
... Several DFA methods to evaluate the efficiency of a product design from a product assembly perspective have been proposed in the literature; the most prominent methods are the [9,[20][21][22][23][24][25][26][27] method-time measurement, manufacturing producibility handbook, Boothroyd and Dewhurst method, assembly evaluation methods, Lucas method, large-size methods, assembly-oriented product design, and DFA sandpit. The aim of these methods is to encompass a diversity of products, processes, and materials. ...
Design for assembly (DFA) is a common engineering technique aiming to reduce assembly costs, increase productivity, and reduce parts cost and material flow. Traditional DFA methods are based on CAD modelling and analysis using specific algorithms comprising the DFA rules. However, such traditional approaches lack of practicality and capability to consider the assembly know-how of designers and manufacturers. In order to overcome some of the limitations of current DFA methods, in this paper a new DFA system based on a haptic-enabled virtual reality approach is proposed. The proposed system, named haptic-enabled VR design for assembly (HVR-DFA), is able not only to simulate the product assembly and collisions among parts, but also to evaluate the product design and assemblability, and to automatically generate assembly planning data from the virtual assembly task execution. Consequently, the user can interactively assess DFA rules and part interferences during the virtual assembly execution. To evaluate the feasibility of the system, a case study corresponding to the assembly of a mechanical component is presented and analysed. The results have demonstrated that the proposed system is an effective DFA tool and more practical than the traditional methods. Moreover, it benefits from the know-how of the assembly experts.
... In addition, research shows that design for assembly (DFA) and design for manufacture (DFM) can guide designers to minimize the size of parts and reduce the assembly complexity, leading to a low-cost and high-efficiency assembly process [3,4]. However, in the actual production process, due to the disconnection between design and manufacturing after the MFA and DFM, the low reusability of design information makes it difficult to support the optimal design of products through the manufacturing data [5]. At the same time, product design data are difficult to update in real-time with the natural state of actual processing. ...
Digital twins are proposed to manage the industrial production sites by mapping physical space entities to virtual spaces. Existing digital twin modeling methods are mainly realized through deploying several modules, including a physical module, a virtual module, a service module, a data module, and a connection module. However, the assembly environment of the aircraft assembly process is complex and challenging to manage. These methods do not provide the data flow and the intrinsic interaction between modules. As a consequence, a digital thread-based modeling digital twin (DTDT) framework with five modules is established in this paper, which takes advantage of both the digital twin and digital thread. Benefited by better data management, the DTDT framework would be conducive to the controllability and traceability of the manufacturing process and product quality. The key characteristics of products, process parameters, and equipment operation conditions, are stored in the database module. And then, the digital thread module will link the entity module and virtual module together by building the directed graph, in which interfaces are provided to the system services module for the process monitoring and processing quality prediction. Finally, the implementation of the DTDT framework is shown through a case of the drilling and riveting process in aircraft assembly. The comparative analysis confirms that this model can improve the efficiency of the aircraft assembly process.
... The paper is a contribution to the improvement of the technological construction of product design methodologies in terms of assembly, i.e. the methodologies for the field of DFA (Design for Assembly) [4]. The main objective of improving the assembly process is mostly to reduce the unit cost per product. ...
In practical applications, statically predetermined pairs are frequently encountered. Designers use them to improve product stiffness. This paper describes a method to reduce the effects of problematic assembly in sliding pairs, which are often statically predetermined. Additionally, it addresses the crucial assembly problem of repetitive accuracy, particularly in assembly line design.
... Steel structures in construction are sensitive to deformation [9,10]. Briefly, the current study focuses on the manufacturing process, installation process, 3D reconstruction, and reverse modeling [4,9,11]. ...
Steel structures that benefit from having lightweight, ductility, and seismic behaviors are capable of improving the overall performance of civil engineering in environmental protection, project quality, process management, and ease of construction, making the procedure more feasible for builders. The application of steel structure techniques has been widely used in bridges, tall buildings, and complex projects around the world. Increasing demand for planning and design has led to structural projects upgrading in structural complexity and geometrical irregularity. However, steel structure projects are still limited by the principal disadvantage of susceptibility to deformation. Therefore, the challenges of the assembly and manufacturing process for steel structures are important. In this paper, to achieve full-loop tracking and control of the assembly and manufacturing process, we propose an integrated approach to undertake the aforementioned challenges via digital twin technology, which combines three modules: (1) deformation detection, (2) pose estimation and optimization, and (3) deformation correction and pose control. This proposed methodology innovatively merges gravitational deformation analysis with geometrical error analysis. Furthermore, the validity of this method’s implementation is demonstrated by the New Shougang Bridge project. The results show that the assembly precision satisfies the standard of less than H/4000, nearing H/6000. Moreover, the elevation difference is less than 20 mm, which satisfies the control precision of the geometric pose. The new method that we propose in this paper provides new ideas for structural deformation control and high-precision assembly, as it realizes dynamic deformation sensing, real-time deviation analysis and manufacturing, and efficient optimization of the assembly process.
In recent years, the demand for smarter and more customized products has increased. Traditional manufacturing systems are typically designed for mass production, which is not suitable for producing customized products. It requires a new manufacturing system that is flexible, scalable, and reconfigurable, for example, a matrix-structured manufacturing system. As the manufacturing system and product design form a symbiotic relationship, products should also be designed for the new manufacturing system to optimize performance. This paper presents a four-stage methodology to improve the product and product family design targeted production in matrix-structured manufacturing systems. The four stages include a product family analysis, indicator calculations, product optimization, and digital twin-based verification and validation. The proposed methodology is applied in a laboratory case study. The result shows that the improved product design has a significantly higher design efficiency than the original ones. We conclude that the methodology of Design for Matrix-Structured Manufacturing Systems has a holistic view on the product family and can optimize the production efficiency in matrix-structured manufacturing systems.
The increasing gap in shopfloor operators’ skillset regarding advanced information and communication technologies along with workforce’s diversity require a cognitive system bridging such technical gaps in order to address evolving production demands and satisfy the human need for self-fulfillment and self-actualization at work. This study discusses on a two-level collaborative filtering approach to improve the distribution of information content provided to an operator for completing a manufacturing activity while considering his or her feedback. A prototype implementation is evaluated in a case study related to the operator’s job rotation on a shopfloor that involves multiple workstations and tasks.
The assembly process is sometimes blocked due to excessive dimension deviations during large-scale assembly. It is inefficient to improve the assembly quality by trial assembly, inspection, and accuracy compensation in the case of excessive deviations. Therefore, assemblability prediction by analyzing the measurement data, assembly accuracy requirements, and the pose of parts is an effective way to discover the assembly deviations in advance for measurement-assisted assembly. In this paper, a coordination space model is constructed based on a small displacement torsor and assembly accuracy requirements. An assemblability analysis method is proposed to check whether the assembly can be executed directly. Aiming at the incoordination problem, an assemblability optimization method based on the union coordination space is proposed. Finally, taking the space manipulator assembly as an example, the result shows that the proposed method can improve assemblability with a better assembly quality and less workload compared to the least-squares method.
Design for manufacture and assembly (DfMA) has become a buzzword amid the global resurgence of prefabrication and construction industrialization. Some argued that DfMA is hardly new, as there are concepts such as buildability, lean construction, value management, and integrated project delivery in place already. Others believe that DfMA is a new direction to future construction. This paper aims to review the development of DfMA in manufacturing and its status quo in construction, and clarify its similarities and differences to other concepts. A multi-step research method is adopted in this study: First, an analytical framework is generated; Secondly, a literature review is conducted on DfMA in general, and DfMA-like concepts in the AEC industry; The third step is to compare DfMA with related concepts. This study reveals that DfMA as a philosophy is hardly new in construction, and the empirical implementation of many DfMA guidelines has begun in the AEC industry. The findings suggested that DfMA is a new and mixed ‘cocktail’ of opportunities and challenges to improve construction productivity with the advancement of construction materials, production and assembly technologies, and ever-strengthened logistics and supply chain management. This study sheds light on three research directions: DfMA implementation and guidance strategies, DfMA frameworks and blueprints, and applications in cast in-situ or intermediate prefabrication construction. Our research findings provide a synopsis of DfMA research and development in construction. This paper can also serve as a point of departure for future theoretical and empirical explorations.
The pursuit of modern product sophistication and production efficiency has bolstered Design for Manufacture and Assembly (DfMA) around the world. Being both a design philosophy and a methodology, DfMA has existed in manufacturing for decades. It is coming into vogue in construction as a potential solution to the industry’s lackluster productivity amid enduring exhortation of cross-sectoral learning. However, many studies of DfMA in construction are still simply following the DfMA guidelines developed from manufacturing without adequately considering important differences between the two sectors of construction and manufacturing. This study aims to develop a series of construction-oriented DfMA guidelines by adopting a mixed-method approach. It critiques existing DfMA guidelines in relation to the characteristics of construction, and further argues that construction-oriented DfMA should consider five fundamental aspects: contextual basis, technology rationalization, logistics optimization, component integration, and material-lightening, either individually or collectively. A case study is then conducted to substantiate and verify the feasibility of these guidelines. This research sheds new light on the cross-sectoral learning of DfMA from manufacturing to construction. The guidelines can be used as the benchmark for the evaluation of manufacturability and assemblability in practice. It also opens up a new avenue for further DfMA studies in construction.
This paper describes a new design methodology for long life and large size (Ll-Ls) product assembly, which has been developed modifying and merging existing Design for Assembly (DfA) methodologies to adapt them to the particularities of this kind of products. These goods are often formed by different large and heavy subcomponents that need to be assembled and commissioned on field, which require the use of several people or special machinery, aspects that are not considered in traditional DfA methodologies. The new methodology, through a Lucas-Hull DfA methodology based approach, gives the chance to evaluate and enhance different design options in the design phase without the need to construct and test prototypes, which are usually quite expensive for this typology of products. An in-house tool has been created to help the designer in the evaluation of different options, where the identifications of the critical features that penalize the assembly of Ll-Ls products are easily identifiable. A case study has been carried out over a solar tracker to test the new approach where design efficiency has been optimized up to 20.4 percentage points through the advices given by the methodology. This means that the optimized design can save up to the 22.8% of the assembly cost in an standard 4.6MW plant, which usually has up to 850 solar trackers. Yet, although the results are really promising, the need to study and add logistic factors to the methodology for this kind of products has been proven, as involved high costs in the whole installation process need to be considered
Design for Assembly (DFA) methodologies help the designer to take into account the assembly process during the development phases of a product (specifications, conceptual design and detailed design), thus improving the assembly process of the product. After a bibliographic review, it is verified that the most extended DFA methodologies are: Boothroyd-Dewhurst method, Lucas method, Hitachi AEM method and Modified Westinghouse method. All these methodologies help to achieve improvements in some of the development phases, but none of them assist the designer in all the phases of the process.
This article presents a DFA methodology that considers the assembly process of a product during all the phases of its development (DFA-SPDP). For this purpose, DFA-SPDP method is created from the four most widespread methodologies. This methodology brings together the main quantitative parameters of the four methodologies in a single method. As a conclusion, applying DFA-SPDP method, the designer is supported throughout the process of developing a product, with information equivalent to that resulting from the application of the four methodologies.
The fast development of smart sensors and wearable devices has provided the opportunity to develop intelligent operator workspaces. The resultant Human-Cyber-Physical Systems (H-CPS) integrate the operators into flexible and multipurpose manufacturing processes. The primary enabling factor of the resultant Operator 4.0 paradigm is the integration of advanced sensor and actuator technologies and communications solutions. This work provides an extensive overview of these technologies and highlights that the design of future workplaces should be based on the concept of intelligent space.
In a manufacturing shop floor, context-aware intelligent service systems can be used to provide information services to shop floor personnel, according to their situation. This article presents an industrial Internet of things (IIoT) context-aware information system that provides decision support for mobile or static operators and supervisors. The system uniquely combines key IIoT concepts such as multi-layered, service-oriented architecture, which integrates several subsystems, such as sensor data acquisition together with concepts for developing context-aware systems such as context modelling and contextual data information provision. The proposed solution is relevant for several manufacturing environments. However, in dynamic, semi-structured manufacturing environments that the workstations are not fixed but dynamically change over time and in which the workers are mobile and not static to some predefined workstations, the utilisation of context-aware information delivery is considered as even more relevant. For that reason, a case study with a medium-sized shipyard has been selected and conducted. Industrial requirements were gathered and led to use cases for a customised implementation of the proposed solution into a shipyard. The proposed solution includes a number of context-aware apps that support the users in carrying out production tasks. The study provided insights into the suitability of the solution presented in the shipyard environment and brought to light further aspects that would improve the proposed context-aware system.
In this paper, emerging technologies in the automotive assembly are discussed, along with techniques used in the vehicle assembly plants. The discussion involves technologies directly dealing with assembly processes such as handling, joining, human resources etc. as well as with supporting systems, mainly the information technologies. An overview of the existing technologies is provided. The assembly systems are unable to cope with the requirements of mass customization and need to be enriched with new technologies for a higher flexibility potential. Concepts integrating various new technologies into supporting both automated and human based assembly operations are presented and discussed versus this identified inability for mass customization. Future assembly plants need to utilize flexibility systematically, both for the system design and its operation. For this purpose, a close loop approach is discussed.
The benefits of integrated design and manufacturing systems in mid to high volume production are widely accepted. The low production volume, large component size and high complexity product domain is less well served by this technology. Examples of this kind of product are machine tools, ships, aircraft and buildings. Design for assembly techniques are a method by which design and manufacture can be integrated and aid the realization of full-process concurrent engineering. Quantifies the significance of this product domain to the UK economy, describes the particular nature of these designs for assembly processes, reviews existing work in the field and specifies the problems encountered. Defines an industrial and academic solution programme. Proposes an integrated approach to applying design for assembly to this repetitive direct engineering domain.
Traditional Design for Assembly methods are limited to part sizes between a few millimeters to a few tens of centimeters in overall size and to part weights under a few kilograms. Parts in the range of a meter in overall size and weighing a few tens of kilograms are examined in this paper. An experimental plan separates weight, mass and inertia and correlates these properties with assembly difficulty and time. When windage, part flexibility and operator fatigue are absent, a set of three parameters serve to model these effects on human assembly performance. Adaptation of this result is made to extend a Design for Assembly methodology.
The Assemblability Evaluation Method (AEM) is an effective tool developed by Hitachi, Ltd. to improve design quality for better assembly producibility. The AEM has been widely used by the Hitachi Group as well as by more than 20 other well-known companies around the world. Using this method, in the early design stage, product design quality is analyzed quantitatively and weaknesses in the design's assembly producibility are highlighted. In addition, the effects of design improvements are confirmed with respect to assembly cost. Through these activities, design improvement is realized. In order to improve the functionality and the accuracy of the method to allow a wide variety of use, the extended AEM has been developed. Based on a constructed product and process model, a new evaluation system has been developed and part-based cost estimation has been realized. In this paper, the concept, theory, evaluation procedure, and accuracy of the extended method are described.
Traditional Design for Assembly methods are limited to part sizes between a few millimeters to a few tens of centimeters in overall size and to part weights under a few kilograms. Parts in the range of a meter in overall size and weighing a few tens of kilograms are examined in this paper. An experimental plan separates weight, mass, and inertia and correlates these properties with assembly difficulty and time. When windage, part flexibility, and operator fatigue are absent, a set of three parameters serve to model these effects on human assembly performance. Adaptation of this result is made to extend a Design for Assembly methodology.
The need for a method of estimating assembly times for large products during the product design phase is discussed. An approach to the development of a database of part acquisition and handling times is described and some preliminary results are presented. Comments and conclusions are made regarding the feasibility of the proposed approach.
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