Publications

Rising and increasingly volatile energy prices resulting from increased power feeds from renewable sources such as solar and wind energy are confronting manufacturers with new challenges. If these companies procure their power supplies at ?uctuating short-term prices from electricity exchanges or through energy purchasing pools, they can in?uence the result-ing energy costs through production control via its actuating variables while energy consumption remains constant. A form of sequencing that decides at short notice which order will be processed next shows particularly high potential. The energy price-oriented sequencing rule that is introduced in this article prioritises orders with a high energy requirement at times when energy prices are low and gives precedence to orders that require less energy at times when energy prices are high, without neglecting the scheduled completion deadline. However, this sequencing rule can only be applied e?ectively under certain preconditions. These are elaborated in this article by means of a simulation study that will con?rm the way the rule functions.

production planning and control, manufacturing control, sequencing, energy costs

Lot sizing is an important task of production planning and control: basis of lot sizes are order change costs and costs for storage. Models for lot sizing do not consider lot size dependent maintenance costs. However, for a forging company the tool wear is very important, because the tooling costs represent a major part in the production cost. In this article, the deter-ministic lot size model of Andler is extended with lot size dependent maintenance costs. For this purpose, the correlation between lot size and the tool wear is ?rst derived in order to develop a lot size dependent wear function. The linking of a lot size dependent wear function with maintenance costs results in a lot size dependent maintenance cost function, which can be integrated into existing lot size models with a customized total cost function. The validation of the extended lot size model consists of two parts. In the ?rst part, the functionality of the extended lot size model is validated. In the second part, a sensitivity analysis of the lot size is carried out with regard to lot size dependent costs and unit costs.

lot sizing, tool wear, forging industry, sensitivity analysis

In this paper, investigations about the displacement of the joining-zone of serially arranged semi-finished hybrid parts durig cross-wedge rolling are presented. The investigated material combinations are steel-steel (C22 and 41Cr4) and steel-aluminum (20MnCr5 and AlSi1MgMn). The rolling process is designed using FEM-simulations and the cross-wedge rolling process was experimentally investigated afterwards. Research priorities are investigations of the displacement of the joining-zone depending on the main parameters of cross wedge rolling. It could be shown that the forming behaviour of serially arranged hybrid parts made of steel-steel and steel-aluminum can be described using FEM. The deviation of the simulated displacement of the joining-zone compared to the trials is only about 3 %, which is a good approximation.

cross-wedge rolling, steel, aluminum, joining-zone

The investigation of thin flash generation in a precision forging process of an aluminum long part using finite elements analysis (FEA) and corresponding forging trials is described in the presentation. Thin flash generation leads to bad handling and positioning in subsequent process steps and therefore tolerance defects. For investigation purpose, the forging processes were varied by use of different preforms with equal volumes but different mass distributions, while the geometrical parameters of the final part were not varied. 

The forging processes were analyzed by FEA with focus on the value of the form-filling simultaneity depending on the preform geometry. Afterwards, corresponding forging trials were carried out for validation.The results of the experiments and the FEA showed good agreement concerning the part areas were thin flash generation was predicted by FEA and actually occurred in experiments.Preforms with higher values of form-filling simultaneity showed less thin flash generation while preforms with lower values of form-filling simultaneity showed significantly increased thin flash generation.

forging, aluminum, FEA, thin flash generation, prediction

Manufacturing individual products at almost the prices of mass products – using 3D printers. The Lower Saxony Center for Additive Manufacturing offers small and medium-sized enterprises (SMEs) free-of-charge support for the introduction of the new technology.

3D printing, additive manufacturing, individual products

As a result of the increasing feed-in of renewable energies, the volatility of the electricity price rises. Considering this, manufacturers can save energy costs by applying an energy price-oriented sequencing rule. Since the application of this sequencing rule does not only have an impact on the energy costs, a potential analysis is presented in this article which, in addition to the energy costs, also considers the schedule compliance cost of production orders.

cost accounting, manufacturing control, production planning and control

In production, product-related error costs can be reduced by focusing on human production factors, such as considering human performance fluctuations during the day, when production planning with respect to job-shop scheduling. In this article, the flexible job-shop scheduling problem is extended by considering product-related error costs and logistic costs. Product-related error costs are increased by over stressing the operative workers. Logistic costs are based on work in process and throughput time. This cost-based definition enables a production plan to be simultaneously optimized in respect of both error and logistic costs. The product-related error costs and flexible job-shop scheduling problem are described mathematically and a memetic algorithm is also presented as an approach. Within the memetic algorithm, the evolutionary process is supplemented with a local search procedure to improve the ability of solutions and repair procedures to rectify infeasible solutions. The influence of product-related error costs on the total costs of a production plan within job-shop scheduling is presented.

flexible job shop scheduling, memetic algorithm, human perfor-mance fluctuation, error costs

An essential component of belt conveyor systems are the support idlers. Particularly in bulk material handling systems, which are used in demanding terrain with numerous gradients as well as under extreme environmental conditions in tropical and arctic regions, they are exposed to considerable stress. The steadily growing flow rates mean higher loads and speeds for the support idlers. This trend is countered by new drive concepts. For example, belt-driven conveyor systems with internally installed motors are used.

Within a research project, the IPH is developing a dual measuring system that can be used to test both conventional bearing rollers and driven bearing rollers.

driven idlers, test rig, efficiency of conveying systems

In respect to the expansion of renewable energies, temporary oversupplies of electrical energy cause a resulting price decline on the German electricity exchange. The electricity traded on the electricity exchange already shows high price volatility. For this reason, energy storage systems are needed that can balance energy supply and demand to ensure grid stability. The production industry can make a contribution by adjusting its consumption by shifting energy-intensive production steps to times of negative residual load.

energy cost, production planning, requirements, power

The measurement of torque via sensors as well as the generation of torque form the basis of many industrial sectors. Within a research project an optical and non-contact measurement method to detect the absolute rotation angle and torque was developed. For comparison with the current state of the art torque sensors a test stand was built and compared to a reference torque sensor. The results of this validation are presented in the present paper.

torque, rotation angle, optical, validation

The production and logistics divisions are currently under pressure mainly due to the increasing demand for product variability. Interactive assistance systems make an essential contribution to increasing efficiency in these areas. However, SMEs are critically opposed to the introduction of technology because of the lack of general conditions, since this is not a trivial one. If a company plans the implementation of interactive assistance systems in production and logistics, maturity models are suitable for capability analysis and support in the planning and control of this process. However, it is important to follow a systematic process for the development of the models, in order to ensure a successful implementation of the assistance systems in the company. 

industry 4.0, digitization, interactive assistance systems, data glasses, maturity models

The investigation of thin flash generation in a precision forging process of an aluminum long part using finite elements analysis (FEA) and corresponding forging trials is described in the presentation. Thin flash generation leads to bad handling and positioning in subsequent process steps and therefore tolerance defects. For investigation purpose, the forging processes were varied by use of different preforms with equal volumes but different mass distributions, while the geometrical parameters of the final part were not varied. 

The forging processes were analyzed by FEA with focus on the value of the form-filling simultaneity depending on the preform geometry. Afterwards, corresponding forging trials were carried out for validation.The results of the experiments and the FEA showed good agreement concerning the part areas were thin flash generation was predicted by FEA and actually occurred in experiments.Preforms with higher values of form-filling simultaneity showed less thin flash generation while preforms with lower values of form-filling simultaneity showed significantly increased thin flash generation.

forging, flashless forging, aluminum, FEA, thin flash, prediction

The generation of bulk metal forming processes needs a lot of time. Researchers construct and simulate many days until a forming sequence without defects is found. At IPH a algorithm is supposed to predict a simulation result within one minute based on the constructions made. The basis for the prediction are many simulations, which were set up, executed and analysed automatically. This article decribes one possible way of doing so.

KImulation, simulation, automation

Marine gearboxes ensure the reliability of the entire ship. Therefore a timely maintenance is crucial. To decrease maintenance costs and increase security, IPH develops a wireless and energy-autonomous measurement system to monitor marine gearboxes from afar.

gearbox, ship, condition monitoring, maintenance

In order to improve the overall efficiency of production facilities through the use of automated guided vehicle systems (AGVs), the availability of the AGVs has to be high. Failures of AGVs have to be minimized. However, if a failure occurs, a successful disturbance management is crucial. Especially for producing companies, economic losses can occur, if material is not at the right place at the right time. Delays can be a hazard to the adherence to delivery dates. In this research project, a support system is developed that automatically generates strategies for the handling of disturbances.

AGV, expert system, automated guided vehicles, case-based reasoning, CBR

Plasma-transferred arc welding (PTA) is a flexible welding process to coat metallic materials with a wide variety of material combinations. At the University of Hanover, this process is currently being qualified for the production of hybrid semi-finished parts for bulk forming products. The technology provides many answers to the questions about cost-effective manufacturing methods in the field of high-performance components. The process shown is a combination of a welding and cross wedge rolling (CWR) process, which is intended to create homogeneous coatings from steel with high carbon equivalents (CEV>0.5). Weak points due to inhomogeneities in later components must be avoided when the parts are used in tribological applications, so the production process has to be very reliable. Therefore it is necessary, that important properties of the joining zone between the material partners such as the coating thickness and metallic microstructure are well known and can be controlled.

The deformation of the weld seams and the microstructure is optically examined. It is shown, that it is possible to convert the original casting structure of the welded layer into a forming structure. The investigations provide a first overview of the possibilities to influence the coating quality by forming processes in the production of welded hybrid semi-finished steel parts.

tailored forming, plasma-transferred arc deposition welding, hybrid parts, cross wedge rolling

In this article, the flexible job-shop scheduling problem is extended by consideration of energy costs which arise owing to the power peak, and further decision variables such as work in process and throughput time are incorporated into the objective function. This enables a production plan to be simultaneously optimized in respect of the real arising energy and logistics costs.

The energy-costs-aware flexible job-shop scheduling problem (EFJSP) which arises is described mathematically, and a memetic algorithm (MA) is presented as a solution. In the MA, the evolutionary process is supplemented with a local search. Furthermore, repair procedures are used in order to rectify any infeasible solutions that have arisen in the evolutionary process. The potential for lowering the real arising costs of a production plan through consideration of energy consumption levels is highlighted.

memetic algorithm, flexible job-shop scheduling, energy-costs, power peak

In the automotive industry, aluminum forged parts must fulfill lightweight and heavy duty performance requirements. The generation of thin flash between die halves and in the small gaps between the die and punch must be prevented during the flashless forging process in completely enclosed dies. However, thin flash formation is neither predictable nor preventable.

A numerical model is developed based on finite element analysis to investigate and predict the generation of thin flash in aluminum flashless precision forging processes. The significance and effects of the main influencing input parameters, including billet temperature, forming velocity, and width of gap, on different resulting parameters are evaluated. Among all resulting parameters in the established numerical model, hydrostatic pressure and the forming force in the main forming direction have been identified as the most suitable for predicting thin flash generation.

aluminum forging, forging in completely enclosed dies, flashless forging, FEA

A combined measurement method for the optical determination of the absolute rotational angle and torque was realized. Absolute codings of the angle as well as proper production technologies for the production of suitable markings on the shaft were investigated and successfully implemented.

The absolute rotational angle could be measured with a resolution of about 0.001° at an accuracy of better than 0.2° (corresponds to 0.05% f. s.). Torque was determined with an accuracy of about 3% f. s..

The conclusion is that the overall aim was achieved.

optical measurement, torque, absolute angle of rotation

This lecture discusses the results of the research project "4.0 Ready", and goes into detail about the potentials and barriers of the implementation of interactive assistance systems, especially in the service and maintenance, as well as the support of the implementation by the use of maturity models.

industry 4.0, interactive assistance systems, data glasses, maturity models

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