Material Flow Process Research Articles

Transferable multi-objective factory layout planning using simulation-based deep reinforcement learning

Factory layout planning aims at finding an optimized layout configuration under consideration of varying influences such as the material flow characteristics. Manual layout planning can be characterized as a complex decision-making process due to a large number of possible placement options. Automated planning approaches aim at reducing the manual planning effort by generating optimized layout variants in the early stages of layout planning. Recent developments have introduced deep Reinforcement Learning (RL) based planning approaches that allow to optimize a layout under consideration of a single optimization criterion. However, within layout planning, multiple partially conflicting planning objectives have to be considered. Such multiple objectives are not considered by existing RL-based approaches. This paper addresses this research gap by presenting a novel deep RL-based layout planning approach that allows consideration of multiple objectives for optimization. Furthermore, existing RL-based planning approaches only consider analytically formulated objectives such as the transportation distance. Consequently, dynamic influences in the material flow are neglected which can result in higher operational costs of the future factory. To address this issue, a discrete event simulation module is developed that allows simulating manufacturing and material flow processes simultaneously for any layout configuration generated by the RL approach. Consequently, the presented approach considers material flow simulation results for multi-objective optimization. To investigate the capabilities of RL-based factory layout planning, different RL architectures are compared based on a simplified application scenario. Throughput time, media supply, and material flow clarity are considered as optimization objectives. The best performing architecture is then applied to an exemplary application scenario and compared with the results obtained by a combined version of the genetic algorithm and tabu search, the non-dominated sorting genetic algorithm, and the optimal solution. Finally, two industrial planning scenarios, one focusing on brownfield and one on greenfield planning, are considered. The results show that the performance of RL compared to meta-heuristics depends on the considered computation time. With time the results generated by the RL approach exceed the quality of the best conventional solution by up to 11%. Finally, the potential of applying transfer learning is investigated for three different application scenarios. It is observed that RL can learn generalized patterns for factory layout planning, which allows to significantly reduce the required training time and can lead to improved solution quality. Thus, the use of pre-trained RL models shows a substantial performance potential for automated factory layout planning which cannot be achieved with conventional automated planning approaches.

Prediction of various defects and material flow behavior during dissimilar FSW of DH36 shipbuilding steel and marine grade AA5083 using FE-based CEL approach

Dissimilar friction stir welding (FSW) of steel-Al is a very tedious job. Inappropriate welding process parameters can lead to the initiation of inevitable defects associated with dissimilar FSW processes. These can be presented as tunnel defects, void generation, excessive flash formation, and other surface irregularities. Using conventional experimental trials makes it usually challenging to identify such defects. This research adopted an Abaqus/Explicit® framework utilizing a 3D thermo-mechanical based coupled Eulerian-Lagrangian (CEL) methodology. In order to predict commonly observed defects in the FSW process, the proposed FEM uses the volume of fluid approach. By monitoring the material flow into and out of the computational/void domain, the suggested framework has made it feasible to predict surface, sub-surface, and volumetric defects. Defect formation is studied at a constant tool rotation speed of 875 rpm, welding speed of 90 mm min−1, and tilt angle of 0°. Tilt angles of 0° caused welding joints with a small tunnel defect. Thermal history, axial force variation, and material flow behavior are all strongly aligned with the principle of defect generation. An experimental trial has been conducted to validate the proposed finite element model. The previous analysis found that the average axial force closely matches the welding-related experimental findings with a percentage error of 7.85%. While a proportion error of approximately ∼0.57% was found between the compared numerical and experimental diameters of the pin end-hole defect. Furthermore, the proposed model accurately predicted the process of material flow along the thickness direction of the workpiece. It was seen that the stress generated at the root of the flashes reached a higher value ranging between 485.6 and 582.7 MPa. Finally, a good agreement between the numerical results and the experimental trial was established, showing the robustness of the developed computational FEM technique.

The Usability of Craft Layout Design Method with the Examination of Simplifications

Logistics optimization has been increasingly attention by companies in recent decades, but due to the current situation, such as the pandemic, recession, and supply chain reorganizations, manufacturers have to resort to more serious tools. One of these is layout redesign, which fundamentally changes a material flow process. One of the most well-known methods is the CRAFT method, which uses two very serious simplifications. In this work, we will examine how much difference the simplifications make in a system close to reality, and can we safely use the CRAFT method.

城乡景观中土壤生态系统微塑料的来源、迁移特征及其风险

PDF HTML阅读 XML下载 导出引用 引用提醒 城乡景观中土壤生态系统微塑料的来源、迁移特征及其风险 DOI: 10.5846/stxb202104191019 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 中国科学院青年创新促进会项目（2018057）；国家自然科学基金（41590841） Identifying the sources, migration and risks of microplastics in soil ecosystem along urban-rural landscape Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:土壤微塑料污染的持久性、复杂性及其对土壤生态系统的影响受到越来越广泛的关注，但对其来源、迁移过程等仍有许多问题尚未理清。从复合生态系统的角度，通过对城乡景观中土壤微塑料的来源、迁移过程及其风险等相关研究进展进行了系统梳理，分析了城乡不同景观中土壤微塑料的主要来源和特点，讨论了土壤微塑料在城乡景观中的迁移特征及其驱动力，探讨了土壤微塑料在城乡景观中的生态和健康风险。今后需进一步明确城乡景观中土壤微塑料污染的物质流过程与环境归趋特征，加强微塑料对土壤生态系统的作用过程及生态系统服务影响的研究，揭示土壤微塑料对人类健康的直接或间接影响，建立城乡复合生态系统土壤微塑料污染预测模型，以维护土壤生态安全与人居环境健康。 Abstract:Microplastics, as an emerging pollutant, have been widely concerned by public and science community because of its persistence, complexity in environment and significant influences on soil ecosystem. Identifying the sources, migration and risks of soil microplastics along urban-rural landscape has becoming an urgent issue. Based on recent published literatures on soil microplastics, this study reviewed the sources, migration characteristics and ecological risks of soil microplastics in urban-rural environment by considering the dynamics of urban-rural complex ecosystem. The main sources and input characteristics of soil microplastics in different landscapes along urban-rural landscape were analyzed. The migration characteristics and driving forces of soil microplastics in urban-rural landscape were demonstrated. Furthermore, effects of soil microplastics on ecological and healthy risks were discussed. This study suggested that the impacts of soil microplastics on terrestrial ecosystem should be clearly explored as a critical issue for current studies and identifying the material flow process and environmental fate of soil microplastics in urban-rural environment can provide effective solutions. The direct and indirect impacts of microplastics on human health in different landscape patterns are widely concerned by public and are also an urgent issue to be explored. Furthermore, modelling on soil microplastics contamination based on its spatial and temporal variability in urban-rural complex ecosystem is another critical issue and should be highlighted for future study. 参考文献 相似文献 引证文献

THE CONCEPT AND ESSENCE OF INVENTORIES IN THE LOGISTICS SYSTEM OF AN ENTERPRISE

This article describes the concepts: inventories, strategic inventories, the meaning and essence of inventory management system, the reasons for the creation of inventories. Inventories in one form or another are present along the entire length of the logistics chain, both in production and in circulation. The article summarizes the general characteristics of models and methods of inventory management. It is determined that, in general, inventories are a form of material flow, a crucial marketing tool and a strategic means of improving competitive positions in the commodity market. The main function of inventories is to ensure the continuity of the process of social reproduction. At all stages of the cycle of resources and products of labor, material (commodity) flows act as one or another inventory. It is substantiated that inventories occupy a special place in the property and dominant positions in the cost structure of enterprises in various fields in determining the results of economic activity of the enterprise and in covering information about its financial condition. It is noted that an important aspect is the need to create inventories in logistics systems and maintain inventory levels at such a level to ensure uninterrupted supply of all units with the necessary material resources, provided compliance with the cost-effectiveness of the entire process of material flow. The purpose of this article is to study the term “inventories” and the main features of the category of inventories based on an analysis of the approaches of various scientists to this question. In the logistics system of a manufacturing enterprise, one of the objects of management is the flow of inventory, which is presented in the form of inventories. Inventories began to be seen as a form of material flow that has its limits in time and space.

Parallel Velocity Extension for Level-Set-Based Material Flow on Hierarchical Meshes in Process TCAD

The level-set method is widely used for high-accuracy 3-D topography simulations in process technology computer-aided design (TCAD) because of its robustness to topological changes introduced by the involved complicated physical phenomena. Particularly challenging are material flow processes, such as oxidation, reflow, and silicidation, as these require the solution of intricate physical models and the extension of the model-dependent velocity fields to the entire simulation domain at every time step to accurately compute the advection. This velocity extension, thus, introduces yet another computational burden at every time step, which is significant when considering that high-accuracy material flow simulations can easily require several hundred time steps and are applied multiple times in cutting-edge fabrication processes of integrated circuits. In this work, a shared-memory parallel scalar and vector velocity extension algorithm for level-set-based material flow simulations on hierarchical meshes is introduced, allowing to further reduce the turnaround time of TCAD workflows. The performance is evaluated by investigating a representative material flow simulation of 3-D thermal oxidation of silicon. A parallel speedup of 7.1 for the vector-valued extension and 6.6 for the scalar-valued extension is achieved for ten threads; the latter outperforms a previous approach by up to 60%.

Proposal for the flow of material and adjustments to the storage system of an external service provider

Abstract This article deals with issues related to the flow of material to the assembly line and examines the possibilities of reducing the costs of this process. It is based on the current state of the transport of individual parts to the producing company and the storage system using Kanban and Just in Sequence (JIS) logistics technologies, and the subsequent collection of material for transport to the assembly line. The change in the system of transport technology has led to a reduction of the total storage space and costs, and at the same time, the processes related to storage and collection of parts have been simplified. The whole process of material flow to the assembly line is solved using the real supply system via the JIS technology, together with the system of receipt and storage of components in connection with individual operations during the handling and storage of these components, and their picking and transport to the assembly line. Evidently, the change in the system and the associated savings can also be employed to warehouses and manufacturing companies of the automotive industry, which use automated assembly lines with the timing of the assembly process of the final product.

Homogenised model for the electrical current distribution within a submerged arc furnace for silicon production

Silicon is produced in submerged arc furnaces which are heated by electric currents passing through the furnace. It is important to understand the distribution of heating within the furnace in order to accurately model the silicon production process, yet many existing studies neglect aspects of this current flow. In the present paper, we formulate a model that couples the electrical current to thermal, material flow and chemical processes in the furnace. We then exploit disparate timescales to homogenise the model over the timescale of the alternating current, deriving averaged equations for the slow evolution of the system. Our numerical simulations predict a minimum applied current that is required in order to obtain steady-state solutions of the homogenised model and show that for high enough applied currents, two spatially heterogeneous steady-state solutions exist, with distinct crater sizes. We show that the system evolves to the steady state with a larger crater radius and explain this behaviour in terms of the overall power balance typically found within a furnace. We find that the industrial practice of stoking furnaces increases the overall rate of material consumption in the furnace, thereby improving the efficiency of silicon production.

The influence of the shoulder depth on the properties of the thin sheet joint made by FSW technology

PurposeThis paper aims to experimentally determine the influence of the tool shoulder depth value on the structural and strength properties of the single lap joints made of 7075-T6 aluminium alloy made with friction stir welding (FSW) technology. The aim of the preliminary tests is to optimize the parameters of joining process of thin-walled structures such as the skin-stringer joint or skin-frame joint of the aircraft fuselage. The tests were carried out for materials commonly used in such structures, i.e. 1.6 mm thick sheet 7075–T6 aluminium alloy with cladding on both sides (cladding thickness 4% per each side). The layer of clad protects plates from corrosion.Design/methodology/approachThis study shows the results of the investigation for the joining of 7075–T6 ALCLAD aluminium alloy sheets. The welding process was carried out on a computer numerical control milling machine SOLARUCE TA–20A. Linear FSW welding was performed using a commercial tool from RSS SCHILLING with the symbol 10–K–4–Z–M–O, which is fabricated of hot work tool steel. Constant parameters of the technological process were applied. The welding process was executed for different values of the shoulder depth ZS.FindingsThis paper investigated the dependence between the thinning of the welded material and the depth value of the tool shoulder during the FSW process. The influence of the depth value of tool shoulder on joint strength in the static tensile/shear test was also performed. With the increase of the depth of the tool, the size of flash and structures of the face of the joint changes as well (its annular surface resulting from the tool’s work and the accompanying process of material flow on the run-off side). Such conditions in the process require a proper tool depression to reduce the occurrence of flash and minimize material thinning to achieve high joint strength and maintain the conditions for plasticizing the material.Practical implicationsBased on the experimental tests carried out, a number of guidelines for the correct conduct of the welding process can be outlined.Originality/valueTaking into account the various aspects of the process, the optimal range of the tool depth into the material is a value of approximately 0.06 mm. At this value, the face of the weld is not porous; the flash is easily removed; and the strength of the joint and the deformation of contact line are at an acceptable quality level.

Wireless Control for Smart Manufacturing: Recent Approaches and Open Challenges

Smart manufacturing aims to overcome the limitations of today's rigid assembly lines by making the material flow and manufacturing process more flexible, versatile, and scalable. The main economic drivers are higher resource and cost efficiency as the manufacturers can more quickly adapt to changing market needs and also increase the lifespan of their production sites. The ability to close feedback loops fast and reliably over long distances among mobile robots, remote sensors, and human operators is a key enabler for smart manufacturing. Thus, this article provides a perspective on control and coordination over wireless networks. Based on an analysis of real-world use cases, we identify the main technical challenges that need to be solved to close the large gap between the current state of the art in industry and the vision of smart manufacturing. We discuss to what extent existing control-over-wireless solutions in the literature address those challenges, including our own approach toward a tight integration of control and wireless communication. In addition to a theoretical analysis of closed-loop stability, practical experiments on a cyber-physical testbed demonstrate that our approach supports relevant smart manufacturing scenarios. The article concludes with a discussion of open challenges and future research directions.

TO THE SUBSTANTIATION OF THE STORAGE BUNKER DESIGN FOR A HIGH-ACCURACY VOLUMETRIC DOSING DEVICE

The paper substantiates the design of one of the main components of a high-precision volumetric dosing device for bulk materials - its storage hopper. It is determined that hopper structural design should avoid possible hang-ups of the product processed and maintain rather uniform dense packing of the material on its way to the dosing area. The process of bulk material flow in a storage hopper was studied numerically by discrete element method. It is concluded that hopper design should be axially symmetric, with defect-free walls, and expanding at an angle of 2-4° to its base.

Using look-ahead plans to improve material flow processes on construction projects when using BIM and RFID technologies

PurposeBuilding information modelling (BIM) and radio frequency identification (RFID) technologies have been extensively explored to improve supply chain visibility and coordination of material flow processes, particularly in the pursuit of Industry 4.0. It remains challenging, however, to effectively use these technologies to enable the precise and reliable coordination of material flow processes. This paper aims to propose a new workflow designed to include the use of detailed look-ahead plans when using BIM and RFID technologies, which can accurately track and match both the dynamic site needs and supply status of materials.Design/methodology/approachThe new workflow is designed according to lean theory and is modeled using business process modeling notation. To digitally support the workflow, an integrated BIM-RFID database system is constructed that links information on material demands with look-ahead plans. The new workflow is then used to manage material flows in the erection of an office building with prefabricated columns. The performance of the new workflow is compared with that of a traditional workflow, using discrete event simulations. The input for the simulations was derived from expert opinion in semi-structured interviews.FindingsThe new workflow enables contractors to better observe on-site status and differences between the actual and planned material requirements, as well as to alert suppliers if necessary. The simulation results indicate that the new workflow has the potential to reduce the duration of the material flow processes by 16.1% compared with the traditional workflow.Research limitations/implicationsThe new workflow is illustrated using a real-world-like situation with input data based on expert opinion. Although the workflow shows potential, it should be tested on a real-world site.Practical implicationsThe new workflow allows project participants to combine detailed near-term look-ahead plans with BIM and RFID technologies to better manage material flow processes. It is particularly useful for the management of engineer-to-order components considering the dynamic site progress.Originality/valueThe research improves on existing research focused on using BIM and RFID technologies to improve material flow processes by showing how the workflow can be adapted to use detailed look-ahead plans. It reinforces data-driven construction material management practices through improved visibility and reliability in planning and control of material flow processes.

Determination the efficiency of open mixing screws

Our goal is the determination of the material flow processes around the mixing screws and introducing a new mixing index which can characterize the performance of open mixing screws. The validation of the new discrete element model is demonstrated by experimental results of our self-developed apparatus. To quantify the mixing efficiency of open mixing screws we use the value of mixed volume around the screws. Sensitivity analysis is used to analyze how the different values of leaf diameter, pitch and angular velocity affect the mixed volume.

Decision Support Simulation Method for Process Improvement of Electronic Product Testing Systems

Spread of the Jidoka concept can be phrased as a trend at the production of electronic products. In most of the cases, with the application of this concept, the development of testing procedures (for quality assurance purposes) of the finished products can be avoided. In those cases, when the production process of the appropriate quality product cannot be implemented safely for the establishment of the product testing process (following the production process), changing the number of variety products, change of requirements concerning the electronic products (e.g., instructions related to energy consumption, noise level) and the variation of the required testing capacity make the modification of the established testing process necessary. The implementation of related plans often leads to problems (e.g., not the appropriate storage area, material flow process or material handling equipment having been chosen). The method of process configuration affects the sustainability, since the poorly established process can lead to additional usage of non-renewable natural resources and unjustified environmental impact. For one of the tools of Industry 4.0, we developed such a state-of-the-art testing method with the use of simulation modelling by which the change of testing process can be effectively examined and evaluated, thus we can prevent the unnecessary planning failures. The application of the developed method is also shown through a case study.

Logisztika 4.0 megoldások az okos gyárban

Meeting the dynamically changing needs of customers’ demands, the development of Industry 4.0 capabilities for companies engaged in production and service activities in order to increase efficiency and expand their capacity. These goals require digitization, strengthening the integration of technologies, and widespread deployment of cloud-based services. This revolution is becoming incredibly popular among companies and affects the business world in three main areas: Through the integration of horizontal/vertical value chains, through the digitization of products and services, and the development of the digital business model and customer relationships. In this article, we present the material and information flow processes that take place in a smart factory operating according to the principles of Industry 4.0.

Influence of tool thread pitch on material flow and thermal process in friction stir welding

A three-dimensional transient computational fluid dynamics model is developed to analyze the influence of tool thread pitch on the material flow and thermal process in friction stir welding (FSW) of aluminum alloy plates. Four tool designs with different thread pitch are considered, the information of material flow velocity in the shear layer is extracted by analyzing the distribution of the tracking particles which are released at the starting points of streamlines, and the effect of thread pitch on material flow velocity is examined. Pin thread can effectively prevent the speed sudden change at advancing side, which is easy to occur with unthreaded pin. The total heat generation decreases with increase in thread pitch, which results in the decrease in peak temperature in FSW process. The calculated and measured thermal cycles and thermo-mechanically affected zone boundary match with each other.

Physical modeling of material flows in cyber-physical production systems

Cyber-physical production systems that produce customized products usually show complex material flows. Furthermore - due to customization - work pieces that are transported within these production systems strongly vary in terms of their physical properties. In combination, this increases the probability of physically induced material flow disturbances, e.g. a work piece falling off a conveyor belt. In case of damaged work pieces or equipment, the occurrence of these events may result in increased delivery times and costs. However, traditional material flow simulations are unable to predict physically induced disturbances, since their discrete-event approach solely focuses on chronological aspects of the material flow. In consequence, this paper presents the development of a computer-based model to simulate physical aspects of material flows by using a physics engine. In the first step, the requirements for this simulation model are determined. This includes the identification and definition of physical phenomena that influence typical material flow processes. Furthermore, a suitable physics engine is selected, that matches the requirements and is able to simulate the relevant physical phenomena. Subsequently, required input data and parameters are defined. After the theoretical framework is developed, the model is implemented using the selected physics engine. Finally, the model is validated by using an exemplary material flow process. The validation determines if the simulation model is capable of simulating physical aspects in material flows with a suitable degree of reality.

MECHANICAL VIBRATION AND SHOCK MEASUREMENT OF MATERIAL FLOW DEVICES AND SYSTEMS

The article deals with the measurement and analysis of the vibration of material flow devices and systems. This work has been done to find out if and in what form kinetic energy arises in comprehensive material flow processes. In the first chapter the theory of vibration measurement from periodic vibration to transient effects will be described using their physical and mathematical foundations. In the second chapter will present the results of the large-scale measurements. A special focus is on the natural frequency of the individual material flow devices. It has to be examined whether it is a certain useful frequency of technical units such as trucks, conveyor belt, etc. egsist over the entire supply chain. At the beginning of the article, the theoretical basics of metrology will be described, then the results will be presented and then the results will be summarized and evaluated. At the very end, an outlook is given about the further steps of the work.

Using simulation in layout verification of solar module assembly workshop

Facility layout problem (FLP) contemplates the optimization of space utilization, costs, and material flow. Commercial simulation softwares are commonly used to validate layouts by simulating the real world material flow and production process. To validate a layout scenario of a solar module assembly workshop, a 3D simulation model is presented which was designed on VisualComponents software. To begin with, we introduce the layout characteristics and use the systematic layout planning (SLP) method to design the block layout of workshop. Then, we built components library which contains all the facilities needed in the production line, specifically conveyors, processing equipments, robots, buffers. Finally, we have established a simulation layout model using the components in the customized library according to the block layout, and configured the components which were allocated in the layout by setting the parameters and building the connection between components via signal. To improve the performance of the workshop, we have found the best work-in-process (WIP) value for the workshop and the optimal number of workers. Additionally, the layout model was used to test collision and reachability. It demonstrated the production process in a realistic simulation environment which helped in the sales process as well. The reusable component models we have built make it easy to build a layout within a short time and validate the effectiveness of the layout scenarios for any other projects.

MATERIAL HANDLING MACHINES AND SYSTEMS – UMI-TWINN PROJECT CONTRIBUTION

Nowadays, the Industry 4.0 concept affects every area of the industrial, economic, social and personal sectors. The most significant changings are the automation and the digitalization. This is also true for the material handling processes, where the handling systems use more and more automated machines; planning, operation and optimization of different logistic processes are based on many digital data collected from the material flow process. However, new methods and devices require new solutions which define new research directions. In this paper we describe the state of the art of the material handling researches and draw the role of the UMi-TWINN partner institutes in these fields. As a result of this H2020 EU project, scientific excellence of the University of Miskolc can be increased and new research activities will be started.