Publications

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

Men and machines will soon be working side by side. Researchers at IPH contribute to this trend: They have developed a driverless forklift truck which understands human language and gestures.

Industry 4.0, logistics, autonomous transportation, AGV

High temperatures up to 1280 °C and high pressures during the forming opperation lead to strong tool wear in forging processes. Increasing tool wear can lead to very high costs. By experiments conducted at the Institut für Integrierte Produktion in Hanover the correlation between tool wear and lot size in hot forging processes was verfied. The findings will help companies to optimise maintenance procedures and therefore reduce cost in the future.

forging, steel, tool wear, lot size

A bus rebuilt as factory is presently touring across Lower Saxony and Bremen. The goal: getting small enterprises informed on Industry 4.0. The free roadshows are organized by "Mit uns digital!". Until the end of 2017, there will be another eleven tours.

industry 4.0, digitalization, SMEs

A low energy demand and a fast processing time are required in each industrial process for the production of crankshafts. Crankshafts have a very complex geometry and are forged with a high percentage of flash compared to other forging parts. Recent research showed the feasibility of a flashless forging of crankshafts. One way to forge a flashless crankshaft within three steps is to use cross wedge rolling, multi-directional forging and final forging.

This paper presents the investigation results of the influence of the cross section area reduction in cross wedge rolling on different parameters at multi-directional forging. First, the state of research, the process development and tool design of cross wedge rolling and multi-directional forging are described. Then a parameter study will be presented and the influence of the cross section area reduction on flash generation, billet temperatures, forming degree, forming forces and effective strain are shown. Generally, flash generates because a rotation-symmetric billet is forced into an asymmetric movement. The influence of an increasing cross section area reduction leads to a decreasing amount of flash at the bottom of the crankwebs.

multi-directional forging, cross wedge rolling, crankshaft, parameter study, forming angle

One research topic of the Institut für Integrierte Produktion Hannover (IPH) is the avoidance of worker overload in production during job shop scheduling to eliminate production errors, improve product quality and reduce cost.

job shop scheduling, human performance curve, error costs

A main target in automotive engineering research and development is currently to reduce fuel consumption and CO2 emissions. Therefore in this project lightweight design was combined with material design in order to produce more efficient structural components. The joining process for tubes of steel and aluminum by laser brazing was investigated to create a joint area that is highly formable. These steel-aluminum joints were afterwards hydroformed, at which steel and aluminum parts were formed in a single step. This process is called "IHU-THT" and can provide lightweight components with excellent mechanical properties.

FEA, hydro forming, tailored forming

Most of today’s technical parts and components are made of monolithic materials. These mono-material components produced in established production processes reach their limits due to their respective material characteristics. Thus, a significant increase in production quality and efficiency can only be achieved by combining different materials in one part. Bulk forming of previously joined semi-finished products to net shape hybrid components that consist of two different materials is a promising method to produce parts with locally optimized characteristics. This new production process chain offers a number of advantages compared to conventional manufacturing technologies. Examples are the production of specific load-adapted forged parts with a high level of material utilization, an improvement of the joining zone caused by the following forming process and an easy to implement joining process due to the simple geometries of the semi-finished products.

This paper describes the production process of hybrid steel parts, produced by combining a plasma-transferred arc deposition welding process with a subsequent cross wedge rolling process. This innovative process chain enables the production of hybrid parts. To evaluate the developed process chain, coating thickness of the billet is analysed before and after cross wedge rolling. It could be shown, that the forming process leads to an improvement of the coating, meaning a more homogeneous distribution along the main axis.

process chain, plasma-transferred arc deposition welding, hybrid parts, cross wedge rolling

In recent years, the requirements for technical components have steadily been increasing. This development is intensified by the desire for products with lower weight, smaller size and extended functionality, but also higher resistance against specific stresses.

The superior aim of the Collaborative Research Centre 1153 "Tailored Forming" is to develop potentials for hybrid solid components on the basis of a new process chain by using joined semi-finished workpieces.

This paper presents the approach and first results of selected subprojects for semi-finished workpiece production by composite extrusion presses, for forming the hybrid semi-finished products by means of cross wedge rolling, die forging and extrusion, and numerical failure prediction of the joining zones. This provides an overview of possible lightweight strategies in the area of bulk forming by the use of pre-joined semi-finished workpieces.

tailored forming, semi-finished workpiece production, forming, cross wedge rolling

Different challenges arise in cross wedge rolling hybrid parts depending of the material arrangement (serial or coaxial) which need to be investigated fundamentally first.

In cross wedge rolling of serial components, the controlled forming of the joining zone is the greatest challenge. The forming behaviour of the component halves is different, depending on the flow stress of the materials used. In order to allow the forming process to be carried out in a controlled manner, the forming behaviour was first analysed with regard to the displacement and quality of the joining zone, and then possibilities were determined with which the forming can be effected in a targeted manner. For this purpose, the influencing parameters (workpiece temperature, forming speed, cross-section reduction, shoulder and wedge angle) were determined systematically using the Finite Element method, and the investigations were then verified experimentally. In order to influence the forming behaviour the investigations include structural measures (e.g. unequal tool halves) as well as process-related parameters (e.g. unequal temperature distribution).

Cross wedge rolling of coaxial components has other challenges due to the component construction. The aim is to be able to specifically influence the course of the thickness of the applied coating during the forming. Therefore finite element simulations were carried out to determine the influencing parameters. By a systematic investigation of the test parameters according to the DoE method, the layer thickness before the deformation as well as the cross-section reduction are parameters with the greatest influences on the course of the layer thickness after the deformation gave. The results obtained were subsequently verified in experimental tests.

cross wedge rolling, steel, aluminum, joining zone, coating thickness

This paper proposes a method for the automated generation of roadmaps for AGVs. So far the roadmaps are mostly generated manually, which leads to long and laborious planning phases. The presented method incorporates both mathematical roadmap algorithms as well as human knowledge in the form of a fuzzy inference system. The results of the expert system are evaluated in comparisons to the A* algorithm and to manually generated roadmaps on a real production layout. In both cases the expert system performs better.

fuzzy logic, expert system, AGV, roadmap

Automated guided vehicle systems (AGVS) have become indispensable in advanced production facilities. Due to significant progress in the field of automated guided vehicles (AGVs) and the increased automation within production plants, the potential applications for AGVs increase. The design of the roadmap for automated guided vehicle systems is a time-consuming process which is currently performed manually for the most part. Because of the AGVs increasing degree of complexity a manual design of the roadmap becomes more and more difficult and challenging. In the course of the research project “Automatic design of the roadmap for automated guided vehicle systems” (IG 18007) a software demonstrator was developed which allows the automated generation of the roadmaps for AGVS. The software demonstrator was applied to real reference scenarios and it was proven that the automatically generated roadmaps are as reliable as the manually generated ones and in some cases even more efficient.

fuzzy logic, expert system, AGV, roadmap

The volatility of electricity prices is steadily increasing due to the growing expansion of renewable energies. This is particularly observable at the electricity exchange. Small and medium-sized enterprises (SMEs) in the manufacturing sector can save energy costs due to these fluctuations through targeted load management methods. To increase this potential, SMEs need to use smart meters and obtain their electricity at pricest as close to those at the electricity exchange as possible.

power procurement, electricity exchange, load management, electricity costs

The dismantling of disused industrial facilities such as nuclear power plants or refineries is an enormous challenge for the planning and control of the logistic processes. Existing control models do not meet the requirements for a proper dismantling of industrial plants. Therefore, this paper presents an approach for the control of dismantling and post-processing processes (e.g. decontamination) in plant decommissioning. In contrast to existing approaches, the dismantling sequence and depth are selected depending on the capacity utilization of required post-processing processes by also considering individual characteristics of respective dismantling tasks (e.g. decontamination success rate, uncertainties regarding the process times). The results can be used in the dismantling of industrial plants (e.g. nuclear power plants) to reduce dismantling time and costs by avoiding bottlenecks such as capacity constraints.

dismantling management, logistics planning and control models, nuclear power plant dismantling

Researchers at the Institut für Integrierte Produktion Hannover (IPH) have developed a software programme for an objective evaluation of factory layouts. With this tool, you can select your optimum layout numerically instead of following your gut instincts.

factory planning, layout evaluation, optimization procedures

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