- The IPH
The most common method of bulk forming processes is closed die forging with flash. In these processes a surplus of material is used to avoid forging defects such as a missing filling of the cavities. The surplus material is driven through the flash gap and forms the flash. Therefore, the flash gap design has a distinct influence on the material flow within the die and thereby on the cavity filling, the material usage and other process parameters. In indus-try the flash gap is fixed once the dies are manufactured and cannot be changed without additional manufacturing.
A moveable flash gap, which can be changed vertically during the forging operation, was developed within this thesis. It can be used to influence the material flow within the forming process. Thus, the filling of the cavity can be improved. By the use of a variable flash gap in the forging process of a trial part, a maximum increase in the cavity filling of 4.6 mm (17.2 %) was achieved. Furthermore, the influences of different process properties, such as the billet temperature, the trigger force or the height of the moveable flash gap, were evaluated.
To allow the application of a variable flash gap to different forging parts, a guideline was designed. For that purpose, forging parts were classified into characteristic zones. Within the zones the influence of differently designed flash gaps were evaluated using FEA. The result of this evaluation is a recommendation on possible designs of a variable flash gap for differ-ent forging parts, to allow an improvement of the cavity filling.
bulk forming, finite element analysis (FEA), flash gap, material flow, die design
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
Material efficiency and the development time of a forging sequence are decisive criteria for increasing the economic efficiency in the production of complex forgings. SMEs can often only interpret forging sequences in a shortened form due to insufficient capacities and high competitive pressure. Therefore, a generally valid method is to be developed that automatically generates multi-stage, efficient forging sequences based on the mass distribution of any forged part.
automated process design, die forging, resource efficiency
In lightweight automotive construction, hybrid structures made of various materials as well as solid and sheet metal elements are used. By hybrid compound forging, a sheet steel and a solid aluminium part can already be joined in a material-locking manner during the forming process. The Institut für Integrierte Produktion Hannover (IPH) gGmbH and the Institut für Schweißtechnik und Trennende Fertigungsverfahren (ISAF) of TU Clausthal are investigating how solid aluminium bolts and steel sheets can be joined in a material-locking manner. This article explains the decisive forming parameters. Furthermore, the tool design for the joining tests is presented.
lightweight construction, aluminum, compound forging
The joint is the weak point at a hybrid metal semifinished product in tube hydroforming. In real forming processes, a deformation at the joint would be prevented in order to avoid failure. A better knowledge of the forming behavior enables to reduce the effort in process design. Thus, this study investigates in hybrid material combinations and the forming behavior of the joint area regarding their suitability for tube hydroforming.
hydroforming, tube, steel-aluminum, FEA
Lightweight automotive construction increasingly relies on hybrid structures made of steel and aluminium. These materials are currently joined mainly by form locking, for example by riveting. Welding and bonding are also used for joining the two materials. Hybrid composite forging allows to join the two components during the forming process. This shortens the process chain. With the help of zinc as a brazing material, the components are joined to form a material bond. This publication explains the results of the simulative parameter study. It shows how temperature, geometry and speed influence the joining result. Furthermore, first results of practical joining tests are presented.
lightweight construction, aluminum, simulative parameter study
Constantly increasing quality requirements and ever-stricter conditions pose difficult challenges for the foundry industry. They must produce the high-quality components demanded by the market at a reasonable cost. Modern technologies and innovative methods help to master this challenge. Until recently, production, from the design of the aluminum melting furnace to daily process, relied largely on traditional methods and experience. However, important data and information about the melting process—for example, the temperatures and the shape of the aluminum block in the furnace—can hardly be obtained with conventional experimental methods, as the temperatures exceed 700 °C. Therefore, this research project investigates the method of monitoring a melting process by means of optical sensors for the first time. The purpose of this paper is to predict the surface shape of the block during the melting process, as it is not possible to maintain a constant monitoring due to the heat and energy loss during measurement (Einsatz einer Lichtfeldkamera im Hochtemperaturbereich beim Schmelzvorgang von Aluminium. To generate the necessary data, a 3D light-field camera is installed on top of an aluminum melting furnace in order to monitor the process. The basic idea is to find a general method for curve modeling from scattered range data on the aluminum surface in 3D space. By means of the (x, y, z) data from the 3D camera, the aluminum surface is modeled as a polynomial function with coefficient derived using various interpolation and approximation methods. This study presents an attempt to find the optimal polynomial function model that describes the aluminum surface during the melting process by interpolation or approximation methods. The best method for curve fitting will be extended and implemented for surface modeling.
melting process light-field, polynomial function, interpolation, approximation, aluminum surface
The development of an ecological logistical impact model for the holistic consideration of the logistics performance should allow companies and especially SMEs to be able to record the CO2 emissions of the logistics transparently. For the development of such a model, the basic influencing factors must be defined and furthermore established as quantitatively assessable criteria. This paper discusses the basic relationships between logistics and ecology. Moreover, the boundaries for an ecological and logistical impact model are discussed and procedures for the definition of the required evaluation criteria are described.
Ecology, Logistics, CO2 calculation, Impact Modell, sustainabilty
A hot forging process allows to produce parts of excellent quality and technical properties. Nevertheless, it is not possible to forge undercut geometries like piston pin bores, it is usually necessary to manufacture them in subsequent processes. Thus, an undercut-forging process was newly developed. Such a process requires a multidirectional forming tool, which is challenging due to a high clamping force of the tool during the process. With the research results, the requirements to the crucial tool components of heavy springs diminish, allowing using standard spring devices instead of large and expensive custom designed devices. The aim of this study is to analyze the clamping force, its origin, and influencing factors in order to facilitate the tool design. Therefore, in forming simulations the input parameters press velocity, initial temperature, and punch shape were investigated, and their effect on the clamping force was statistically evaluated. The press velocity has the major impact on the resulting clamping force. The initial part temperature and the shape of the punch tool showed minor but still significant effects. This combination of input parameters reduces the load and the stress on the tool, enabling to perform the process on smaller forging presses. Eventually, forging trials validated the results.
forging, undercut, FEA, multidirectional, clamping force, tool design
In forging industry, the development of new bulk metal forming technologies still is determined by a separation between construction and simulation. The resulting iterations take a lot of time. In this paper, the data mining method neuronal network is used to predict the forming force of a finite element forging simulation of a flange.
simulation, AI, prognosis, forming force
In lightweight construction, light metals like aluminum are used in addition to high-strength steels. However, a welded joint of aluminum and steel leads to the precipitation of brittle, intermetallic phases and contact corrosion. Nevertheless, to use the advantages of this combination in terms of weight saving composite hybrid forging has been developed. In this process, an aluminum solid part and a steel sheet were formed in a single step and joined at the same time with zinc as brazing material. For this purpose, the zinc was applied by hot dipping on the aluminum in order to produce a connection via this layer in a forming process, under pressure and heat. Due to the formed intermediate layer of zinc, the formation of the Fe-Al intermetallic phases and the contact corrosion are excluded. By determining the mathematical relationships between joining parameters and the connection properties the strength of a specific joint geometry could be adjusted to reach the level of conventional joining techniques. In addition to the presentation of the joint properties, the influence of the joining process on the structure of the involved materials is also shown. Furthermore, the failure behavior under static tensile and shear stress will be shown.
lightweight construction, aluminum, joining properties
In this paper, the investigation of thin flash generation in precision forging process of an aluminum long flat part is described. The aim was to derive a predictive simulation method for thin flash generation in order to increase both process and part quality in the future. The forging processes were varied by use of different preforms with equal volumes but different mass distributions while using the same final part geometry. The experimentally forged parts were analyzed concerning the amount and part area of the generated thin flash. The conducted FE simulations were analyzed concerning the hydrostatic pressure values p in the part areas near to the tool gap between upper and lower die immediately before form-filling. For a more detailed comparison, single p values were included to hydrostatic pressure functions P. The comparison between the P functions and the experimentally determined thin flash height shows, that high pressure values as well as high gradients of the P functions indicate less thin flash generation. The method therefore allows a qualitative prediction of thin flash generation. It can provide two kind of information. First: The prediction of the specific locations where thin flash is likely to occur in one final part by use of one single preform. Second: The qualitative prediction of the specific final part areas were thin flash is likely to occur depending on different preform geometries. This method will decreases the necessity of time-consuming forging trials and can shorten the preform designing process in the future.
forging flashless precision forging FEA aluminum predictive simulation method
In the forging industry, like in many other economic sectors, it is common to simulate forming processes before executing experimental trials. An iterative simulation process is more economic than trials only but still takes a lot of time. A simulation with realistic parameters takes many hours. For an economical production the idea of predicting some main results of the simulation by Data mining was developed. Within this paper, the use of four different Data mining methods for the prediction of certain characteristics of a simulated flange forging process are presented. The methods artificial neural network, support vector machine, linear regression and polynomial regression are used to predict forming forces and the lack of volume. Both are important parameters for a successful simulation of a forging process. Regarding both, forging forming forces and lack of volume after the simulation, it is revealed that an artificial neural network is the most suitable.
data mining, artificial neural network, linear and polynomial regression, support vector machine
This paper describes the production process of serially arranged hybrid steel parts, produced by combining a laser welding process with a subsequent cross wedge rolling process. The presented results are only a first approach in order to get first insights in the forming behaviour of laser welded and cross wedge rolled parts. The investigated material combination is C22 (1.0402) and 20MnCr5 (1.7147). This innovative process chain enables the production of hybrid parts. To evaluate the developed process chain, the weld and the joining zone is analysed before and after cross wedge rolling. Main results are that the joining process using laser welding enables a strong bonding between the two materials with a higher hardness in the joining zone than for the individual materials. After the forming process, the bonding of the joining zone is still present, while the hardness decreased but remains higher than of the materials themselves.
tailored forming, laser welding, hybrid parts, cross wedge rolling
The melting process in an aluminum melting furnace cannot be monitored by contact sensors, since the furnace is not accessible due to the high temperatures (more than 700 °C). Therefore, monitoring the melting process by means of optical sensors is investigated for the first time in this research project. This article deals with an innovative optical measuring system that is able to monitor the melting bridge despite the red-hot furnace walls. For this purpose, a light-field camera is installed on top an aluminum melting furnace in order to monitor the process and to control a targeted heat input into the melting furnace using a rotatable burner. The light-field camera used can capture a 3D point cloud with only one image. To achieve this, a separate field of lenses is placed between the image sensor and the main lens, projecting a virtual intermediate image onto the actual image sensor for further data processing. In addition, a self-developed image analysis program serves to monitor the height variation of the aluminum block and any melting rest on the melting bridge of the furnace.
Thus, the energy efficiency of the aluminum melting process could be increased by 15 % and the melting time reduced by almost 20 minutes by means of online monitoring.
light-field camera, process monitoring, image processing, melting process, energy efficiency
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
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 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