Applied Mechanics and Materials Vol. 856

Abstract: Modern assembly lines are usually optimized towards output and tact time as well as process capability and quality. Yet, approaches for energy saving are hardly used in assembly presses. Therefore, assembly lines are using more electric power and compressed air than necessary. Especially at high load, during handling phases and in different idle modes there is a huge potential for energy savings. Current research is focusing on high-power consuming turning and milling machines as well as laser welding. Energy saving projects usually focus on whole factory halls instead of manufacturing lines and single assembly machines. Therefore, this paper presents a new methodology using a top-down-approach and data mining analysis regarding a conventional assembly press as well as a whole assembly line. Here, relevant information types like process data, quality factors, expenditure of energy per produced part and power consumption are used to generate more insight into chained assembly processes. Various tools like energy analysis, process flow and correlation analysis are used to identify focus stations of a whole assembly line for energy saving projects and quality improvements. This novel holistic approach regards the electrical power and compressed air consumption of each relevant station and its machine components during different operating states as well as its correlations between process data, quality factors and energy consumption. Besides tact-time-analysis of the process, the scheduled and unplanned downtimes of the machine are also regarded. Furthermore, it enables predictions of tool wear and breakdown, quality impacts of supplied parts, as well as energy savings on process and machine level. Due to an increased quality, the material efficiency may rise as well.

Abstract: The reflow soldering in electronics production is identified as an energy-intensive process that requires further resource efficiency optimization. A lean-based analysis of the resource consumption in production at different factory levels illustrates the minimum resource consumption and saving potentials in the soldering process. The four levels namely factory, machine, process, and product represent the hierarchical structure within the production facility and establish a transparent overview model. The value-added energy investigation is conducted at all levels, and additionally the exergy method is used in the product level to investigate the material transformation efficiency and the minimum resource consumption in the model. The results in different levels illustrate the energy efficiency of each level, the energy wastage, and the potential for further optimization.

Abstract: This paper describes an overall, simulation-based optimization approach to control plant operations for manufacturing calcium silicate masonry units (CS), which is directed towards and thus immediately applicable to practical processes. Starting from an investigation and classification of the CS production in order to differentiate the properties of each sub-process, specific target criteria are derived. To enable the influencing of these targets, relevant parameters including their mutual interdependencies are identified. On this basis, the criticality of each process step is assessed in order to determine improvement potentials and to investigate possible adjustments to the parameters.The elementary production types indicate a mix of the discontinuous and continuous processing in CS plants. Particularly, this work shows that through interrupting the continuous material flow, the hardening process is the main criteria for a plant’s success in meeting its targets, especially concerning energy efficiency. To achieve a feasible approach, the work develops a solving method geared to an optimized hardening process.Therefore, a formulation of a measureable target system is established, which is the prerequisite for modeling the whole optimization problem. An expedient decomposition of this optimization model to smaller sub-problems provides an efficient solving of these complex job-scheduling problems, in order to direct the method towards an operative use. The paper concludes with the determination of potential solving procedures for the overall problem and appropriate algorithms for solving the sub-problems.

Abstract: There is a large demand to increase the material and energy efficiency as well as the format-flexibility of packaging machines due to current market changes, e.g. the increased demand for individualized products and the resulting drop down of batch sizes. These machines are mostly customized products to fulfil the special requirements of the various packaging machine users. Thus, it is important to know the most profitable level of material and energy efficiency as well as format-flexibility for these machines at the beginning of the development phase. The focus of this paper is the introduction of a new model for the economical assessment of format-flexible packaging machines. It is targeted towards machine manufactures during the early stages of development as well as potential machine users in the investment decision process. Further, the model is applicable to consider further capability characteristics of different packaging machines. The introduced model combines the net present value method and the overall equipment effectiveness system. The application of the economic evaluation model will be shown by a practical use case.

Abstract: Nowadays material flow in factories is realized by different concepts of transport. Each of those specific conveyers has pros and cons due to its concept. In general, the state of art of transport systems have a low flexibility of the path planning and are not suitable for dynamic transport requirements, wherefore they are designed for a specific application. Generally, the common systems cover a specific task of transportation and can fulfill a predefined maximum amount of transportation orders. Due to the effects of mass-customization there is an increase of the variance of the products combined with a reduction of the number of units per variation and a volatile costumer demand. Therefore, it is necessary that the next generations of production lines, especially the intralogistics transportation systems, have to be designed more adaptable and flexible. The object of the research in this paper is a cyber-physical material flow system with flexible, autonomous and collaborative vehicles combined with centralized sensors to digitalize the workspace. Furthermore, the number of vehicles in the system can be adjusted to the volume of the transport requirement, wherefore the system is suitable for different tasks in the intralogistics. Due to the approach of a decentralized digitalization of the workspace on the one hand side and the decentralized architecture of the path planning and order allocation system on the other hand side the concept lead to a nearly endless scalability of the system. The scalability is only restricted by the maximum number of entities which can use the communication system. Therefore, it is possible that the system adjust itself to the actual intralogistics demand as well as the dimension of the field of operation. This lead to a self-adjustable intralogistics transportation system which avoid a physical redesign of the whole system if the intralogistics demand is changing. To validate the approach, the decentralized intelligence of the transport entities and the production units is implemented in a discrete event simulation. In this simulation environment different task allocation methods, sizes of the transportation fleet, lot size management concepts and site layout concepts can be compared and rated which each other.

Abstract: This paper describes possibilities of process and condition data acquisition on universal milling centers with Sinumerik 840D-sl control. The measurement and process data is gathered mostly with the present control system architecture of the machine tool. This internal data collection has been extended by additional sensors and an external measurement system to enable further and partially deeper analysis. This setup is also explained in this publication. The demonstrator together with the measuring system allows an investigation of the introduced components close to reality and the observation of the overall system at once. The latter is considered energetically on a comparative measurement to ascertain discrepancies in energy consumption between two different milling strategies for a pocket cycle.

Abstract: This study, which focuses on analyzing aluminum melting and die casting procedures is part of the Smart Melting project in the research network Green Factory Bavaria (GFB). The aim of the present research project is to investigate these procedures and to suggest measures to increase the overall energy efficiency. The analysis starts with the capture of the operating structure, the relations between supply and consumption of liquid aluminum and an evaluation of aluminum furnaces themselves. The study concentrates on shaft furnaces whose specific energy consumption is 25 % higher than stated by the manufacturers. At the same time the melting capacity of the furnaces ranges at the lower end according to the manufacturer's data. The reason for this deviation is a discontinuous operation mode due to demand fluctuations. Consequently the flue gas has still a high temperature which means a high waste of energy. Based on these facts the furnace charge and operation mode have to be optimized and the high temperature flue gas can be used to preheat the pig aluminum.A numerical model of aluminum furnaces is applied to investigate this optimization potential. This model can simulate either a single aluminum furnace (case 1) or a furnace integrated in the entire manufacturing plant (case 2). The advantage of case 1 is the furnace's operation on its most efficient point because there is no influence of the die casting process. In case 1 an improvement of the furnace charge leads to a higher capacity utilization and therefore to a reduction of 30 % specific energy consumption and a 50 % increase of melting capacity. Whereas in case 2 the simulation of the entire manufacturing plant results in a rise of 25 % melting capacity and a 16 % decrease of specific energy consumption. The simulation proved increasing energy efficiency due to preheating the pig aluminum in both cases.

Abstract: In many applications conventional lubricants which are based on mineral oils cannot be used because it is physically impossible or forbidden by regulations. Operating machine elements, such as rolling element bearings, under dry running conditions is highly demanding in regard to the materials that are being used. Applying thin films to steel substrates was identified as an approach to achieve wear resistant and low friction surfaces at reasonable cost. Furthermore, a substitution of mineral oil based lubricants by coatings is an achievement in terms of sustainability, environmental friendliness and conserving resources. In this paper wear and friction behaviour of deep groove ball bearings with two types of diamond-like-carbon (DLC) coating systems on the inner and the outer ring are investigated. The coating systems are modified hydrogenated amorphous carbon films, one with a metallic doping element (a‑C:H:Me) functional layer and one with a non-metallic (a‑C:H:X). As ball materials hardened steel (100Cr6) and ceramics (Si₃N₄) are considered. The tests have been conducted on a four-bearing-test-rig under radial load and a constant rotational speed. The combination of a‑C:H:Me with Si₃N₄ balls shows the best results in this sample by reaching the predefined time limit without exhibiting an increase in the friction torque trend.

Abstract: Cryogenic machining offers advantages compared to conventional cooling lubrication strategies particularly for difficult-to-cut and high-temperature-resistant materials such as titanium and nickel alloys. For implementation purposes environmental and cost factors are crucial for this new machining approach in series production. In order to facilitate investments it is mandatory to evaluate the technology’s potential prior to the final implementation decision. In the field of machining, in particular machining with cryogenic process cooling, there is no standardized and uniform procedure to assess this potential. In this paper a systematic approach and underlying analysis tool will be introduced to determine the potential of cryogenic processing in terms of resources and energy efficiency of the manufacturing operation. This approach satisfies the general conditions in a reasonable assessment effort as well as in the detail level. With this analysis tool, real production and process data are compared with results from scientific cryogenic tests and research and examined with regards to their applicability. Thus, it is possible in an early stage of the production to identify potentials in manufacturing and to take measures to realize these effects. In case cryogenic processing of a specific material has not been carried out so far, the similarity of this material to existing research results is determined. If positively assessed, the surrogates’ potential is transferred with a specific safety factor to the material. The analysis tool has been applied and refined in a real large-scale series production as well as in a complex component manufacturing and the holistic potential for e. g. durability, material removal rate (MRR) or savings regarding the use of metal working fluids (MWF) have been identified.

Abstract: This contribution firstly presents results gathered during the development of a lightweight multifunctional trailer made of composite material. Focusing on various cross country activities, such as mountain biking, hiking or trail running, significant technical improvements compared to existent products were obtained. This includes technical features like an integrated design to reduce accelerated mass, increase flexibility and provide shock suspension for the child carried during sports activities. As a key feature of the trailer, an agile steering system was engineered to both fit the specific requirements during the trailer’s use as a stroller and as a baby jogger. Due to the integrated design the weight of the single child prototype trailer was reduced by up to 50 % compared to conventional models and the driving comfort was considerably increased. To evaluate both the safety of the carried child during sports activities and the comfort for the adult as well as - last but not least - the resulting fun of those both users during sports activities a series of test rides was conducted. Selected results of the developed measuring setup and test track design are presented in this paper. Finally gathered measurement data are discussed and further design improvements are derived.