Search

Digital twins are representations of real-world systems in the digital world, relying on physical system data to optimise, manipulate, detect, and interact. The requirements of digital twins diverge depending on the application in focus. The complexity ranges from simple to highly complex use cases, which increases setup time and reduces maintainability. Therefore, different representations and views of the digital twin are necessary, e.g., file type conversions or abstractions of geometry. Standards that try to solve these problems are ISO 21597, by providing containerisation and linkage of data, and ITU-T Y.3090 and ISO 23247, by providing frameworks to support the creation process of digital twins. Based on these standards, this paper aims to enable a holistic view of digital twin applications in flexible manufacturing cells to reduce the implementation effort when the system is installed or changes. We identify a digital twin's most relevant features, parameters, and assets. This feature set is categorised regarding the frequency of changes. The main observable manufacturing elements are machine tools, robots, peripheral devices like autonomous mobile robots (AMRs), manufacturing utilities like tools, and processes. Various information systems depend on or interact with these manufacturing cells, e.g., CAM, PLM, MES, tool management, fleet control, and cell control. While applying the framework of ISO 23247 to a flexible manufacturing cell, we found that life cycle changes are only considered for products and not for the digital twin itself. Therefore we try to emphasise life cycle changes by linking the manufacturing cell to a life cycle meta-layer, simplifying the design, deployment, and updates of digital twin applications. This linkage remains valid through changes, reducing application maintenance effort by allowing re-instantiation of the applications. Therefore, a multidimensional representation of the physical layer can address rapidly changing real-time data to hardly changing life cycle information. [ABSTRACT FROM AUTHOR]

In the sheet metal industry, companies rely on nesting procedures to organise the cut patterns of sheet metal. Most of the current nesting algorithms and methods focus solely on laying out the cutting patterns only to reduce material usage. However, in dynamic manufacturing environments, such as engineer to order (ETO) companies, efficient nesting has to be addressed together with effective production scheduling. Therefore, reducing the trade-off between high material utilisation (to lower production cost) and effective production planning (to honour tight delivery deadlines) is essential. This paper presents a novel scheduled nesting approach for ETO companies. The framework is built on the existing "scheduled nesting" model, where material utilisation and variables implied from different operations around the nesting process are considered together. The proposed artifact, called Scheduled Nesting System (SNS), is based on a constrained optimisation objective function to be minimised and considers a wide range of variables, which are either directly or indirectly connected with nesting. These variables are material usage, operation of cutting machine cost, cost of changing metal sheets, cost of cutting orders to stock, and order due date, to name a few. The dynamic nature of the ETO operations is as such included by adapting pending nests based on incoming orders. Based on these variables, the framework finds a nest, which has a minimal cost. The study focuses on ETO companies' sheet metal nesting process, and test results show the SNS's potential for lead-time and production cost reduction. [ABSTRACT FROM AUTHOR]

This paper contributes to a novel approach for analysing and quantifying the benefits for reconfigurable cellular manufacturing and assembly systems (RCMS/RCAS), also known as Matrix production, based on modelling and dynamic simulation. International market trends concerning consumer behaviour and demand result in increasing flexibility requirements, which conventional production lines struggle to meet, thus creating the need for flexible production and assembly systems such as Matrix production. The flexibility results in additional variables and thus a more complex system behaviour. To utilize its benefits, the design and setup of a matrix production is crucial and for potential real-world applications. However, methods to quantitatively assess beneficial features of a matrix production are only beginning to appear in the literature, making decision-making for a production system transformation challenging. This paper contributes a simulation-based approach to analyse the performance benefits of matrix production using modelling and dynamic simulation. The method is demonstrated with a simplified automotive assembly use case for a dynamic multi-variant production. The results confirm the feasibility of the method and quantify the potential for increased assembly system performance gained from specific flexibility features in a matrix production. [ABSTRACT FROM AUTHOR]

Assembly systems are required to be more flexible due to unpredictable resource and demand fluctuations. Line-less assembly systems (LAS) implement flexible job routes through multi-purpose resources and flexible transportation systems. Moreover, a completely reactive layout through (re-)arrangement of stations with mobile resources enables reconfigurations without interrupting production. A scheduling that can handle the complexity of dynamic events is necessary to plan job routes and control transportation in such an assembly system. Since the system layout and the job scheduling influence each other, only an integrated view of layout planning and scheduling implements a reactive system behaviour. Existing pre-planning methods with fixed cycle times are not designed for reactive layout optimization during line-less assembly operations with mobile resources. Therefore, the contribution of this paper is an integrated online optimization architecture for layout evolution using mobile resources and simultaneous job scheduling to increase the efficiency of LAS. The optimization is implemented using modular matching and scheduling algorithms considering temporary station setup states and parallel processing based on zone restrictions. The proposed algorithms are connected to a modular discrete-event simulation and scenario analysis tool of LAS. The simulation and control architecture is validated by applying an industry-based use case. The reactive layout evolution, including station exchanges and mobile resource repositioning are benchmarked with nonflexible control methods. Results show that the developed control system allows for shorter average lead-time and increased throughput and utilization of (mobile) resources. [ABSTRACT FROM AUTHOR]

The current market trends have focused on personalization, where products based on the same platform can have different variations so they can satisfy multiple market segments. Trying to keep up with these trends, industries have introduced hybrid Human Robot Collaborative stations that offer short throughput times, along with the flexibility to process different tasks. For this kind of flexibility to be achieved in production, a concept is examined for remotely reprograming industrial robots. As a result, a fully automated assembly line or a production station, could be repurposed to handle different products or processes, using the currently installed equipment with minor adjustments. The concept that is described in this paper presents a teleoperation – based method for process design and control of industrial robots utilizing Virtual Reality. The main aim is to reduce the time and effort required for repurposing the robot operation without the physical presence of a robot operator at the shop floor. A case study is presented to demonstrate the above described concept. [ABSTRACT FROM AUTHOR]

In small and medium-sized enterprises, the wiring of control cabinets is a very time-consuming process as it is mostly performed manually. Thus, a novel automated approach for wiring control cabinets with batch size 1 is provided. The task is executed by a lightweight robot and based on an ECAD model of a wired cabinet. Therefore, a method is described to export digital data from ECAD and adjust the digital information to real-world conditions. To detect the approximate real-world poses of the components, a 2D image from a stationary visual sensor is used for CAD-based template matching by normalized cross-correlation. A high accurate visual 3D sensor that is mounted on the robot end-effector is moved to the approximate poses of the component ports to measure the exact poses. The results prove the functionality of the developed method, which allows to position the robotic end-effector based on ECAD data, which is the prerequisite to measure the component port with high accuracy using the 3D sensor. [ABSTRACT FROM AUTHOR]

The wiring of control cabinets in small and medium-sized enterprises is a mostly manually performed process and very time-consuming. Thus, an automated approach for wiring control cabinets is necessary. The proposed solution is based on an ECAD model and performed by a lightweight robot. Before the wire insertion, the tip pose of the gripped wire end and the component port pose are detected by processing 3D sensor data. The sensor is able to detect wire ends with arbitrary cross-section geometries and arbitrary component port shapes. The results prove the functionality of correcting the pose of the robot end-effector with respect to a component port using a 3D sensor. [ABSTRACT FROM AUTHOR]

This paper presents a method for automating the generation, verification and deployment of robot programs used in prefabrication of walls for family houses. The making of robot programs is today performed manually by experts, i.e. implying high costs. This is a huge disadvantage since each wall can be unique. The work demonstrates, with implementation and testing, a method to automate the generation of robot programs for fabrication of walls made of wood. This includes the task of generating collision free paths, automatic verification of path performance and deploying to a real industrial robot with minimal human interaction. [ABSTRACT FROM AUTHOR]

In the architecture and construction sector the increasing wish for individualization is often expressed in complex-shaped freeform buildings. Due to missing universal and mature construction methods, freeform buildings are usually realized using customized solutions often including material-consuming substructures, while the visible skin has neither structural nor functional properties. In this context a new concept is presented for manufacturing self-supporting lightweight freeform structures that integrates load- bearing, functional properties and façade design in one unit, using a double-layered structure. The realized prototype building demonstrates an efficient lightweight freeform structure with a surface specific weight of less than 16 kg/m². [ABSTRACT FROM AUTHOR]

Abstract: This paper looks at the application of the principals of dimensional analysis to identify relations between key parameters of the production system in order to construct a process model that can quantitatively describe the influence of manufacturing process variables, type of technology employed and the material flow on the integral productivity for both batch and flow production architectures of the aerospace production facilities. This process model allows the construction of closed cycle production chains for aerospace parts that form critical path in the assembly sequence of the final product. This approach has been successfully applied to solve the problem of the manufacturing process sequence and material flow optimization for gas-turbine compressor blades production. In conclusion one can say that the developed production process model allows to obtain a numerical assessment of the change in integral productivity as a result of controlled variation in parameters of the manufacturing system which in turn allows to design effective production systems based on optimization of the system parameters. [Copyright &y& Elsevier]

Abstract: Distortion considerably influences manufacturing costs, especially if thin-walled parts are machined. To ensure a flexible economical machining, novel processes have to be developed to control distortion within the process chain. Then, reworking by straightening during quenching or by costly hard processing can be kept to a minimum. The fundamental concept of ‘Distortion Engineering’ is based on the inverse application of identified distortion potential to compensate geometric deviations. In the case of thin-walled bearing rings the distortion is related to both, deviation of the wall thickness and the shape. These deviations originate mainly from an inhomogeneous material removal and uneven residual stress state in the workpieces subsurface caused by deformations due to clamping forces during the soft-turning. An adapted non-circular finishing cut can counteract the distortion. Previous work showed that the adaption of depth of cut depending on assessed geometric irregularities reduces deviations by at least two-third compared to non-compensated cutting. Compensation to zero deviation needs a deeper understanding; hence disturbances during the compensation cuts are investigated within this paper. An uneven change of subsurface residual stress state has a retro-active effect on the workpieces’ shape. Experimental results illustrate that the mechanical process loads are alternating with oscillation of the depth of cut. However, only an impact of adapted cutting on residual stresses perpendicular to the cutting direction (axial stresses) was detected. So far, it can be concluded that adapted cutting not leads to an unexpected change of out-of-roundness during subsequent heat treatment. Additionally, the results revealed that the compensation potential is highly affected by a change of workpieces’ deformation due to material removal during one longitudinal cut. [Copyright &y& Elsevier]