Dr.-Ing. Malte Stonis

Doctoral thesis

Defects like folds can arise using forging for the production of long flat pieces made of aluminium. A special defect is the formation of inner folds. These can be seen in the grain flow. Inner folds have a negative effect on the dynamic properties of the forged part. As a production process, forging can be divided into single-directional and multi-directional forging. The formation of inner folds was observed at the single-directional forging. By using the multi-directional forging, a forming operation working from different directions, the forming can be set variably. Thus the development of folds can be prevented. A newly developed method can help in the selection of the forming process and in determining an appropriate tool geometry. Here especially the area is adapted, where the development of inner folds occur. Therefore a calculation model was developed. It integrates a computer-aided identification of the inner folds. Using this model, a correction of the parametrically constructed forging tool is possible.

multidirectional-forging, long flat pieces, aluminium, fibre orientation

Publications

Handling hot steel parts weighing several kilos is physically demanding. A new type of forging tongs is designed to reduce stress at work, prevent pain and reduce sick leave.                             

forging, ergonomic, stress reduction

The selection of storage, commissioning and transport systems (sct systems) is very complex due to the large number of available systems on the market and influencing factors. One important influencing factor is automation. To classify the degrees of automation of sct systems and to determine the individually required automation a method is proposed below.

automation, storage, commissioning and transport systems

Upfront investment costs for the tooling of injection molds are the basis for deciding if a mold is tooled and hence if a part is viable for mass-production. If tooling costs are too high, a product may not viable for production. If tooling costs are estimated too low by the tool shop, contract implications may arise.
The goal of this research is to develop a method with humanlike quotation accuracy, achieve standardization, factor in historic quotation data and shorten quotation process times. The machine learning approach developed is based on geometry data of parts and additional meta-information.

injection molding, tooling, industry 4.0

The aim of subproject B1 of the Collaborative Research Center (CRC) 1153 is to determine the formability of novel hybrid semi-finished products by means of incremental forming cross wedge rolling. Main aspect is the forming of hybrid semi-finished products made of steel, aluminium and hard material alloys. In order to reduce the component weight, the use of hybrid semi-finished products makes it possible to manufacture less stressed segments of a previously monolithic component from a light metal. To increase wear resistance, a component area (e.g. a bearing seat) can be coated with a hard material. In addition, process variables (e.g. temperature and force) are to be measured in contact between work piece and tool in the future. There are primarily two material arrangements for the semi-finished products used: coated (coaxial - demonstrator shaft 1) and joined at the front (serial - demonstrator shaft 3). One challenge is the heating of the semi-finished products necessary for forming, since the hybrid semi-finished product has different flow resistances due to the different materials and may have to be heated inhomogeneously in order to enable uniform forming.

cross-wedge rolling, forming, hybrid work pieces, tailored forming, hybrid semi-finished products

Quality assurance methods are a central success factor for the further industrialization of additive manufacturing. This paper presents an approach for an optical inspection system that controls the quality of additive material extrusion layer by layer. The inspection task gets analyzed, hardware components for data acquisition are designed and a first step towards texture-analytical detection of defects is presented.

additive manufacturing, 3d printing, material extrusion, fused deposition modeling, image processing

A product-dependent, individual process development represents a main cost driver in laser material processing. Therefore, the expert system SmQL is being developed in an FQS-funded project, in which process knowledge can be stored in a formalized form and represented in rule form. This is intended to minimize times for setup processes and secure knowledge in the company in the long term.

expert system, industry 4.0, laser materials processing

The Hybrid Forging Process satisfies the needs of modern structural and material lightweight engineering by combining forming and mechanical joining operations within one process. This paper presents an analytical approach for the prediction of symmetrical joining bonds of bulk material and sheet metal. Finite element simulations verify that the analytical approach provides a threshold value for the sheet metal thickness at which the bending elongation is reduced significantly. Furthermore, the analytical approach emphasizes that surpassing the threshold value leads to a saturation of the bending elongation reduction and only marginal benefit is achieved by increasing the sheet metal thickness.

hybrid forging, bonding, joining, elastomechanics, lightweight, multi-material manufacturing

Driverless transport systems are a building block for more efficient production systems in intralogistics, but have weaknesses in human-machine interaction. In a complex research project, a voice-based assignment is being developed, among other things, which is intended to make human-machine interaction more intuitive and increase its acceptance.

automated guided vehicle, augmented reality, smart glasses, voice control

Belt conveyor systems are an excellent way of conveying bulk material. With increasing load and transport distance, these systems become larger and energy efficiency becomes an important factor. Rollers are an integral part of belt conveyor systems. The running behaviour of idlers during operation has an impact on the energy efficiency of the entire system. The development of driven idlers is seen as one way to reduce the energy consumption of belt conveyor systems. This contribution shows that the investigation of conventional and driven idlers under different conditions is necessary and that a test rig for the investigation of these idlers has been developed at the Institut für Integrierte Produktion Hannover.

idlers, rollers, driven idler, bulk material handling

The Collaborative Research Centre 1153 (CRC 1153) “Process chain for the production of hybrid high-performance components through tailored forming” aims to develop new process chains for the production of hybrid bulk components using joined semi-finished workpieces. The subproject B1 investigates the formability of hybrid parts using cross-wedge rolling. This study investigates the reduction of the coating thickness of coaxially arranged semi-finished hybrid parts through cross-wedge rolling. The investigated parts are made of two steels (1.0460 and 1.4718) via laser cladding with hot-wire. The rolling process is designed by finite element (FE)-simulations and later experimentally investigated. Research priorities include investigations of the difference in the coating thickness of the laser cladded 1.4718 before and after cross-wedge rolling depending on the wedge angle, cross-section reduction, and the forming speed. Also, the simulations and the experimental trials are compared to verify the possibility of predicting the thickness via finite element analysis (FEA). The main finding was the ability to describe the forming behavior of coaxially arranged hybrid parts at a cross-section reduction of 20% using FEA. For a cross-section reduction of 70% the results showed a larger deviation between simulation and experimental trials. The deviations were between 0.8% and 26.2%.

cross-wedge rolling, hybrid forming, FEA, coating thickness

Within the Collaborative Research Centre (CRC) 1153 “Tailored Forming “the manufacturing of hybrid bulk components is investigated. Therefore, a process chain consisting of joining, forming, milling and quality control has been established by multiple subprojects.Within subproject B1 of the CRC forming of hybrid parts by the incrementally forming cross-wedge rolling (CWR) process is investigated. The superior aim is to determine process limits and capabilities, when forming parts consisting of different materials joined by varying technologies.

In this paper, the investigation of cross-wedge rolling of serially arranged hybrid parts made of steel and aluminum is described. The focus of the research presented in this publication is the displacement of the joining zone of hybrid parts due to the cross-wedge rolling process. Therefore, finite element simulations have been developed, that allow the investigations of hybrid solid components. After simulation of various variations of the cross-wedge rolling process, i.e.  differently shaped tools and forming velocities, experimental trials were carried out with identical parameter sets. A comparison of simulation and experiment, showed that the simulation model is capable of describing the cross-wedge rolling process of hybrid parts. The standard deviation of the displacement of the joining zone between simulation and experimental trials is 8.8% with regard to all investigated cases.

tailored forming, cross-wedge rolling, material forming, aluminum, steel

Within the Collaborative Research Centre 1153 “Tailored Forming“ a process chain for the manufacturing of hybrid high performance components is developed. Exemplary process steps consist of deposit welding of high performance steel on low-cost steel, pre-shaping by cross-wedge rolling and finishing by milling.
Hard material coatings such as Stellite 6 or Delcrome 253 are used as wear or corrosion protection coatings in industrial applications. Scientists of the Institute of Material Science welded these hard material alloys onto a base material, in this case C22.8, to create a hybrid workpiece. Scientists of the Institut für Integrierte Produktion Hannover have shown that these hybrid workpieces can be formed without defects (e.g. detachment of the coating) by cross-wedge rolling. After forming, the properties of the coatings are retained or in some cases even improved (e.g. the transition zone between base material and coating). By adjustments in the welding process, it was possible to apply the 100Cr6 rolling bearing steel, as of now declared as non-weldable, on the low-cost steel C22.8. 100Cr6 was formed afterwards in its hybrid bonding state with C22.8 by cross-wedge rolling, thus a component-integrated bearing seat was produced. Even after welding and forming, the rolling bearing steel coating could still be quench-hardened to a hardness of over 60 HRC. This paper shows the potential of forming hybrid billets to tailored parts. Since industrially available standard materials can be used for hard material coatings by this approach, even though they are not weldable by conventional methods, it is not necessary to use expensive, for welding designed materials to implement a hybrid component concept.

tailored forming, cross-wedge rolling, hard material coatings, PTA

Within the Collaborative Research Centre (CRC) 1153 Tailored Forming a process chain for the manufacturing of hybrid high performance components is developed. Exemplary process steps consist of deposit welding of high-performance steel onto low cost steel and pre-shaping the component by cross-wedge rolling (CWR), supported by an optical quality control system. A combination of a fringe projection profilometry setup with a thermal imaging camera is used to monitor the components before and after the CWR process. Both geometry and thermal imaging data are combined, assigning temperature values to 3D data points.
In this paper, the acquisition of combined temperature-geometry data is described. The data before and after the CWR is compared to the input and the result data of the forming simulation that was used to design the CWR process. The comparison shows the quality and sustainability of the heating process as well as the influence of the transportation of the hot component prior to forming. Additionally, the accuracy of the used simulation model and software are evaluated by data examination. The examination shows the limits of idealised and simplified assumptions for the simulation, e.g., a homogeneous temperature distribution before forming or the modelling of the heat transfer on contact surfaces.

tailored forming, cross-wedge rolling, material forming, aluminum, steel, optical measurement

The Institute for Integrated Production Hannover develops process technologies for the simultaneous forming and joining of dissimilar materials. In the future, they should enable, for example, sheet-metal solid parts and steel-aluminum connections. This expands the possibilities for cost-efficient multi-material construction methods in the automobile.

forging, hybrid, progressive compound

In current approaches to factory planning, the influences of transport systems are not taken into account in the layout planning process. Means of transport selection and transportation network planning takes place downstream of layout planning. The effects of transport system selection on the design of the factory layout are therefore only considered at the end of the factory planning process. The selection of certain transportation systems can therefore require extensive adjustments to the layout. This article describes a concept for an expert system that integrates transportation network planning into the layout planning process in addition to transportation system selection. The expert system should interpret the expert knowledge for the selection of transport systems on the basis of fuzzy logic and generate the later factory layout, as well as the transport networks, automatically on the basis of defined input data.

factory planning, layout planning, transport systems, fuzzy logic

By using digital tools in the factory planning process, the planning quality can be improved and the duration of the project can be shortened. In order to exploit these potentials, data consistency must be guaranteed throughout the planning process. In this article, digital factory planning tools, used at the Institut für Integrierte Produktion Hannover (IPH), will be presented and their applications and requirements will be discussed.

digital factory planning, factory planning process, data consistency, digital tools

To this day, the design of preforms for hot forging processes is still a manual trial and error process and therefore time consuming. Furthermore, its quality vastly depends on the engineer’s experience. At the same time, the preform is the most influencing stage for the final forging result. To overcome the dependency on the engineer’s experience and time-consuming optimization processes this paper presents and evaluates a preform optimization by an algorithm for cross wedge rolled preforms. This algorithm takes the mass distribution of the final part, the preform volume, the shape complexity, the appearance of folds in the final part and the occurring amount of flash into account. This forms a multi-criteria optimization problem resulting in large search spaces. Therefore, an evolutionary algorithm is introduced. The developed algorithm is tested with the help of a connecting rod to estimate the influence of the algorithm parameters. It is found that the developed algorithm is capable of creating a suitable preform for the given criteria in less than a minute. Furthermore, two of the five given algorithm parameters, the selection pressure und the population size, have significant influence on the optimization duration and quality.

preform optimization, genetic algorithm, cross wedge rolled, adaptive flash

The selection of a storage commissioning and transport system in times of industry 4.0 often takes place based on the automation that these systems bring with them. It is difficult to assert the actual level of automation from these systems. This paper presents general approaches for the determination of automation. After it will give a presentation of the developed method to identify the level of automation from systems.

level of automation, storage, commissioning and transport systems, storage planning, logistics

Bulk-formed components are used in many applications in automotive and plant engineering. The conditions under which the components are manufactured, often at more than 800°C and thousands of tons of forming force, lead to high die wear. One way to reduce wear is to use suitable protective coatings. Initial basic investigations showed that the use of hard Diamond-like Carbon (DLC) wear-resistant coatings can significantly reduce the tribological effects on the die surface. With new methods such as the use of multilayer layer coatings and temperature measurement on the die surface by use of thin layer sensors, the potential of wear protection for semi-hot massive forming is to be investigated and expanded.

DLC, hot forging, wear

The melt level and oxide layer quantity in an aluminum melting furnace cannot be monitored by contact sensors, since the melting bath is not accessible due to the high holding temperature (above 600°C). Therefore, the method of monitoring the melting bath by means of optical sensors is investigated for the first time. For this purpose, suitable optical measuring systems can be applied which will be able to record the melting bath. The height change of the melt is to be elaborated by means of image analysis and any oxide layer on the bath surface is to be detected.

aluminum melting furnace, metling bath monitoring, oxide layer