Process monitoring and the resulting increase in quality through AI are attracting increasing attention in large parts of the manufacturing industry. The possibilities of inline process monitoring of cross-wedge rolling are being investigated as part of the research of the Collaborative Research Center 1153. The aim is to develop a monitoring system that enables inline process control in order to compensate process deviations that occur during the forming process. Therefore, an algorithm is developed that can detect and classify process deviations within a few seconds and while the process is still running. An AI-based image recognition algorithm was applied as part of this research work. The process data was collected as part of a sensitivity study of the process parameters. A parameter study was used to determine optimized hyperparameters for AI modeling that enable a high prediction accuracy. The challenge of the necessary speed of the prediction was tested and validated. The evaluation of the algorithm including the generation of a picture requires 270 ms on average and is therefore fast enough to be used as preparation for process control. The investigations revealed a possibility for data augmentation that significantly increases the predictive accuracy of the models. Leave-One-Out Cross-Validation (LOOCV) was used to conclude the overall performance of the model.
Cross-wedge rolling, Hybrid components, Process monitoring, AI-based image recognition
This article examines how force sensors must be positioned to detect incorrect positioning of forging blanks. For this purpose, simulative investigations are carried out on a die. Positions for possible sensor placement are applied in a grid pattern. The recorded force values of the respective sensors are analyzed to identify those sensors that are particularly suitable for reliably detecting incorrect positioning.
industry 4.0, digitalisation, process monitoring
It was investigated how a grain refinement can be introduced into a cylindrical rolled piece by means of cross rolling in a flat-jaw design. For this purpose, a non-round shape was rolled in and out again. A theoretical preliminary investigation was used to define a suitable parameter field for experimental evaluation. Metallographic investigations showed that cross-rolling had a positive effect on the microstructure, and IPH will inform the client immediately if it becomes apparent that the estimated costs will be exceeded. The execution of work that leads to the estimated expenditure being exceeded shall only take place after consultation with the client.
Cross-Wedge Rolling, fine grain
A major advantage of flashless precision forging is the saving of resources by avoiding excess material. Especially materials with good flow properties, such as aluminum, sometimes lead to the formation of thin flash. Seals have been developed and experimentally tested to prevent thin flash, i.e. the flow of material into tool gaps. The study presented shows the effectiveness of different sealing materials and the ideal sealing geometry.
thin flash, Sealing concept, precision forging, forming technology, process optimization
It was investigated how a grain refinement can be introduced into a cylindrical rolled part with cross rolling in a flatjaw design. For this purpose, a non-circular shape was rolled in and out again. A theoretical preliminary investigation was used to define a suitable parameter field for experimental evaluation. Metallographic investigations showed that cross rolling had a positive effect on the microstructure.
process design, forming technology
Increasing the service life and process reliability of systems plays an important role in terms of sustainable and economical production. Especially in the field of energy-intensive bulk forming, low scrap rates and long tool lifetimes are business critical. This article describes a modular method for AI-supported process monitoring during hot forming within a screw press. With this method, the following deviations can be detected in an integrated process: the height of the semi-finished product, the positions of the die and the position of the semi-finished product. The method was developed using the CRISP-DM standard. A modular sensor concept was developed that can be used for different screw presses and dies. Subsequently a hot forming-optimized test plan was developed to examine individual and overlapping process deviations. By applying various methods of artificial intelligence, a method for process-integrated detection of process deviations was developed. The results of the investigation show the potential of the developed method and offer starting points for the investigation of further process parameters.
Process monitoring, Wear, Hot forming, Predictive maintenance, Quality management
Wear due to thermal and mechanical stresses is one of the major causes of forging die failure. The assessment of die condition and the associated die life is usually based on experience. This paper presents a method to objectively predict the remaining life of a forging die. With this method a prediction based on optical measurements can be calculated. Practical tests show the possible applications. In addition, force measurements are performed and analyzed to determine how wear affects the force distribution in the die. The assessment based on optical measurements allows objective statements about the remaining tool life of forging dies. The analysis of the force measurements shows potential for predicting tool life but needs further investigation.
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Process monitoring, wear, optical measurements, force measurement
In the research project “AutoPress”, the IPH – Institut für Integrierte Produktion Hannover gGmbH and Jobotec GmbH are jointly striving to develop an automated process control of screw presses. By retrofitting and applying an optimization algorithm, the energy demand is to be reduced and the component quality increased.
digitalization, forming technology, production technology
By creating ultrafine-grained microstructures, the properties of a material can be improved. Ultrafine-grained microstructure has high strength combined with high ductility. This paper describes how a rolling process can be used to influence the microstructure of a material. The process is investigated by simulation and process windows are determined using statistical design of experiments for practical testing.
Grain refinement, flat-jaw rolling, non-circular rolling, finite element method
The Collaborative Research Center 1153 is investigating a novel process chain for manufacturing high-performance hybrid components. The combination of aluminum and steel can reduce the weight of components and lead to lower fuel consumption. During welding of aluminum and steel a brittle intermetallic phase is formed that reduces the service life of the component. After welding the workpiece is heated inhomogeneously and hot formed in a cross-wedge rolling process. Since the intermetallic phase grows depending on the temperature during hot forming, temperature control is of great importance. In this paper, the possibility of process-integrated contact temperature measurement with thin film sensors is investigated. For this purpose, the initial temperature distribution after induction heating of the workpiece is determined. Subsequently, cross-wedge rolling is carried out and the data of the thin film sensors are compared to the the temperature measurements after heating. It is shown that thin film sensors inserted into the tool are capable of measuring surface temperatures even at a contact time of 0.041 s. The new process monitoring of the temperature makes it possible to develop a better understanding of the process as well as to further optimize the temperature distribution. In the long term, knowledge of the temperatures in the different materials also makes it possible to derive quality characteristics as well as insights into the causes of possible process errors (e.g. fracture of the joining zone).
cross-wedge rolling, thin-film sensors, hybrid components, aluminum, temperature monitoring
The Collaborative Research Center 1153 is investigating an innovative process chain for the production of hybrid components. The hybrid workpieces are first joined and then formed by cross-wedge rolling. Pinion shafts were manufactured to investigate the behavior of the joining zone under increased complexity of the forming process. For this purpose, six types of workpieces produced by three types of joining processes were formed into pinion shafts. The reference process provides a shaft with a smooth bearing seat. It was found that the increased complexity did not present any challenges compared to the reference processes. A near-net shape geometry was achieved for the pinions made of steel.
hybrid components, cross-wedge rolling, hot forming, laser beam welding, LHWD welding
Work-related illnesses and the resulting employee absences can have a major impact on productivity and competitiveness, especially in small and medium-sized enterprises. Particularly in the forging industry, the manual handling of forged parts leads to high physical stress and thus to frequent illnesses of the musculoskeletal system, especially of the hand-arm system. One possibility to counteract this circumstance is the use of ergonomic forging tongs. In the study presented here, the influence of ergonomic forging tongs on the physical stress of forging employees was investigated by simulation and experiment and compared to conventional forging tongs. Within the simulation and the experimental investigation, forging parts and forging tongs were varied. In the simulation, an ergonomics assessment of the forging situation could be evaluated using the Ergonomic Assessment Worksheet. In the experimental study, gripping force measurements and calorie measurements were used to determine the impact of handling the forging tongs on the forging employees. The results show that the use of the new ergonomically optimized forging tongs can lead to a significant physical relief for the forging employees. The knowledge gained from the ergonomically developed concepts can also be transferred in other industries.
forming technology, ergonomics
Forgings are produced in several process steps, the so-called forging sequence. The design of efficient forging sequences is a very complex and iterative development process. In order to automate this process and to reduce the development time, a method is presented here, which automatically generates multi-stage forging sequences for different forging geometries on the basis of the component geometry (STL file). The method was developed for closed die forging. The individual modules of this forging sequence design method (FSD method) as well as the functioning of the algorithm for the generation of the intermediate forms are presented. The method is applied to different forgings with different geometrical characteristics. The generated forging sequences are checked with FE simulations for the quality criteria form filling and freedom from folds. The simulation results show that the developed FSD method provides good approximate solutions for an initial design of forging sequences for closed die forging in a short time.
forging sequence, forging sequence planning, automation
Process Optimization through Thin Flash Prevention. Due to the good flow properties of aluminum, the material tends to flow into tool gaps during flashless precision forging and produce the so-called thin flash. For the industrial implementation of flashless precision forging processes, an innovative prediction method for thin flash as well as sealing concepts are to be developed in cooperation with an industrial partner. Simulative studies show that local form filling does not correlate with high pressure or an increased potential for thin flash.
thin flash, FEM-simulation, sealing concepts, precision forging, forming technology
In the non-circular rolling, the feasibility of rolling several mutually offset, locally non-round shaped elements into a cylindrical semi-finished product are investigated. One sub-area of the investigations is the rolling of two elliptical sections.
From three different calculation concepts for the determination of the tool engraving, one was chosen for a simulative parameter study. The main influencing variables, including the length and width of the engraving and a process window, were identified.
forming technology, manufacturing technology, FEM
In order to make the production of complex geometries as efficient as possible, several forming stages are generally used. In these, the billet is first heated homogeneously and then forged via several preliminary and intermediate stages as well as final forming. Previous investigations have shown that significant material savings can be achieved by using inhomogeneous, rather than homogeneous, billet heating. A limiting factor in the practical implementation of inhomogeneous heating is the temperature gradient between the hot and warm regions of the billet.
This study therefore investigates the influence of the length of the temperature gradient on the blank size required to achieve form filling for a given finished part geometry. For this purpose, a simulative parameter study was carried out with three temperature transitions of different lengths and two different finished part sizes.
It was shown that, depending on the finished part size and the length of the temperature gradient, between 3.31% and 17.49% material can be saved compared to a homogeneously heated billet. The length of the temperature gradient thus has a significant influence on the material savings potential.
bulk forming, inhomogeneous heating, resource efficiency, FEA
Process monitoring strategies allow wear-related conditions of forging dies to be detected and predicted. The prediction of the wear condition allows intelligent maintenance strategies. This allows residual tool life to be fully utilized, scrap to be reduced and downtime to be calculated. The content of this article is an economic analysis for calculating the payback period of a process monitoring system.
forging, process monitoring, economic efficiency
In manual solid forming, hand-guided forging tongs are used when processing forged parts. During the forging process, employees are physically stressed by high forging part weights and transmitted impacts. This physical stress leads to employee health limitations and increases absenteeism rates. Ergonomic forging tongs have been developed at IPH that lead to a relief of the forging employees.
ergonomics, forging tongs, forming technology, prevention
The results of the wear investigations will allow multidirectional processes in hot forging to be optimized in the future in a low-wear and economical manner. The determined, wear-inducing process parameters within the design guideline represent elementary basic knowledge which can be applied in a process-specific manner. In principle, the economic potential of multi-directional forging processes using of multi-directional forging processes using sliding dies depends on the application and the desired component geometries. Multi-directional forging processes forging processes offer great potential for savings and can be process design using the results obtained, they can achieve high tool life and have a positive influence on the competitive situation of companies. As a result costs for explicitly selected niche components with significantly higher with significantly increased complexity can be reduced in the future with manageable investment costs in the future. In addition to the process-specific optimization of the process parameters, in the future options for mold design adaptation with regard to local cooling or local cooling or thermal insulation of the slide-wedge wedge mechanics, in order to be able to use the systems in automated series automated series production.
Slide tools, process design, economic efficiency, solid forming
Tailored forming is used to produce hybrid components in which the materials used are locally adapted to the diferent types of physical, chemical and tribological requirements. In this paper, a Tailored Forming process chain for the production of a hybrid shaft with a bearing seat is investigated. The process chain consists of the manufacturing steps laser hot-wire cladding, cross-wedge rolling, turning and deep rolling. A cylindrical bar made of mild steel C22.8 is used as the base material, and a cladding of the martensitic valve steel X45CrSi9-3 is applied in the area of the bearing seat to achieve the strength and hardness required. It is investigated how the surface and subsurface properties of the hybrid component, such as hardness, microstructure and residual stress state, change within the process chain. The results are compared with a previous study in which the austenitic stainless steel X2CrNiMo19-12 was investigated as a cladding material. It is shown that the residual stress state after hot forming depends on the thermal expansion coefcients of the cladding material.
Tailored forming, Residual stress, Laser hot-wire cladding, Deep rolling, Hybrid Components
