Please find information, research projects and publications regarding numerical simulations of cold forging processes in this section.

Projects

• Control of material flow in combined cold forging of aluminum components using moving cold forging die components, Institute for Metal Forming Technology (IFU) University of Stuttgart / Germany – Status report July 2013:
  
  Control of material flow during combined extrusion processes by using an automatic controlled additional tool movement axis. Exact knowledge of parameters influencing the flow of material is an important factor to design combi¬ned cold forging processes. Focus of project is to manufacture double-cup-shaped components having one or more branches at one or at both work piece bottom ends. New approach contains a specific kinematic of moving die according to a given velocity profile: so resulting frictional forces and the material flow can be controlled within particular limits. To determine an optimal and robust process design according to predefined work piece geometry software for FEA forming simulation and for CAE multi-objective optimization was coupled. one crucial condition for applying this strategy is given by application of a most accurate simulation model with a low numerical noise. In experimental tests conducted, the movement of die components is automatically controlled along to predefined kinematics which has been optimized in advance.

• Microforming of bulk metal components from band material, Institute of Manufacturing Technology (LFT) Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany:
  
  The interest on mass production of small complex metal components is currently fostered by fields like electronics and micromechanics. A possible approach is seen in a multi-step bulk forming process, limited among scaling problems by handling difficulties between the forming stages. A radical simplification of the positioning of the workpiece is seen in a process in which a metal strip acts both as raw material and support of the workpiece through the different forming stages.  The results of these studies will lead up to a definition of the achievable geometries and a review of further one- and more step forming processes from the strip plane. The finite element simulation of different single step bulk forming processes has driven to the design of a working tool, which represents the experimental set-up for the study of both the single steps of the process and the entire forming chain. The combined analysis of simulation and experiments aims for an optimization of the metal flow during one and more step bulk forming processes. The study of the strip deformation and of different methods of material flow steering will be further conducted and deeper analyzed. In particular, a higher friction coefficient of the punch and a specific geometry of the blankholder are seen as possible solutions for a more effective extrusion process with minor consequences on the handling.

• System Development for Automatic Controlled (AC) of Cold Forging Processes, Institute for Metal Forming Technology (IFU) University of Stuttgart / Germany – Status report July 2013:
  
  Increasing diversity of variants of parts shape today demands high flexibility of bulk metal forming processes in industry. Moreover flexible fabrication of components means quick reaction to production disruptions and design changes due to volatile customer requirements. Expanding of forming limits or technical advancements of cold forging processes for that reason often demand process combinations and/or additional moveable tool axis. Furthermore automatic controlled tool axis integrated into the cold forging die provides the possibility to react on unexpected process fluctuations during series production leading to net-shape manufacturing. Main objective of this project is the development of a modular designed material flow control system for cold forging applications. Up to now it looks possible to control combined cold forging processes by using a dedicated hydraulic power system for moving least one component of die. Such additional movement of certain die components or additional die axes can be managed dependent or independent from press ram movement. For this purpose a tool rack with an automatic controllable servo-hydraulic movement axis was built up at IFU for implementation into a single-action press. Applying particular knowledge gained by manufacturing parts by a flexible tool rack having one additional controllable axis in this project a second tool rack with two additional servo-hydraulic axes was designed and tested for its application during cold forging. Optimized setpoint curves of additional tool axes actually are determined by using CAE based optimization and numerical simulation. Aim of this project is to integrate an additional controlled axis of motion into a cold forging tool in order to control material flow of complex cold forging parts during forging.

• Influences of various punch shapes on radial cold extrusion process of the three-pillar universal joint pin,  Hefei University of Technology, China:
  
  The metal flow, extrusion force and punch equivalent stress distribution were analyzed through the results of simulation and physical experiments. The investigation shows that the optimized taper angle of the punch was beneficial for the metal to fill the cavity, and it can suppress the rapid increase of forming load during the end stage. What’s more, the cold enclosed die forging process was tried to produce planetary gears. A special structure “shunt cavity” was introduced to reduce the forming load. Consequently, it has verified the feasibility of the process.
  
  
• Internal thread formation process, simulation and equipment, Nanjing University of Aeronautics and Astronautics, China:
  
  Under the same conditions of the process parameters, the internal thread formation by cold extrusion based on low-frequency vibration exhibits a higher rate of thread teeth height and fewer defects of the teeth top than traditional methods, and improve the fatigue strength and surface morphology of the thread so formed. The analysis data during the forming process including extrusion torque and extrusion temperature which made great difference to the thread quality and tap life were derived based on the numerical simulation. The effect of the structural parameters of the extrusion tap on the torque during the forming process is analyzed based on the theoretical formula. The time and frequency analysis of vibration signal for the cold extrusion forming of internal thread was proposed. Dynamic simulation was done for a vibration processing equipment of internal thread formed by cold extrusion based on low frequency vibration.
  
  
  
• Manufacturing Error-free Goods at First Time, Institute of Manufacturing Technology (LFT) Friedrich-Alexander-Universität Erlangen-Nürnberg, Gernmany:
  
  The EU-project MEGaFiT (Manufacturing Error-free Goods at First Try) sets its goal in the reduction of the number of defects, and consequently costs, in manufacturing of complex high-precision metal parts. This will be achieved by developing and integrating in-depth process knowledge, in-line measurement and real-time adaptive process control. This method will be applied to two different production technologies: additive manufacturing and multi-step microforming. Within this project, the Chair of Manufacturing Technology is focusing on simulative and experimental studies of a microcoining process which is part of the multi-step microforming. The main achievements of the first half of the project consist in the detailed design of the microcoining step and of its FE model. By the integration of each step of the microforming process it was also possible to study their interactions. Based on multiple material characterization tests, a complex material model was developed, ensuring high reliability of the simulations. The resulting process knowledge allows the identification of the critical parameters which can be adjusted by the control system in mass production.
  
  
• Reduction of friction in EHD-contacts by microstructured surfaces of components – design, layout and manufacturing by forming, Institute of Manufacturing Technology (LFT) Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany:
  
  Subproject within the Priority Program 1551 “Resource efficient design elements” In highly loaded revolving sliding contacts, like for cam tappet matchings, friction in the contact zone of components can be reduced by specifically applied, well-defined microstructures. Likewise, the wear behavior of such microstructured surfaces determines the durability of components. Within the scope of this project a simulation based method will be developed in collaboration with a partner institute in Erlangen that allows the design of microstructures specifically adapted for the individual tribological load collective. A focus of the LFT-part is the elaboration of the technological basis for a repeatable production of components with microstructured surfaces by a combined extrusion micro coining process coping with the demands of large-lot production. Due to its filigree geometries accuracy of manufacturing of the micro coining punch by micro electrical discharge machining plays a significant role. For an overall view of the product life cycle the characterization of microstructured surfaces is of vital importance as a junction between design and manufacturing of the components as well as for the analysis of wear behavior in operation.
  
  
• Analysis and simulation of cavities and microstructure development during open forging operations, Institute for Metal Forming (IMF) TU Bergakademie Freiberg, Germany:
  
  Larger steel ingots contain internal cavities that have to be eliminated by means of forging. Until now numerical simulations have been related to experimental investigations dealing with artificial cavities. However, there is the problem which criterion for the closing and bonding of the voids is to be used and how realistic it is. Currently the aim is to characterize natural cavities and microstructure behavior before and after forging.
  
  
• FEM FORGING - Continuous Training of Specialists on Design and Optimization of hot, warm and cold forging processes using FEM simulation technologies project (2012-1-ES1-LEO05-48343), Italy:
  
  FEM FORGING’s aim is to design, develop and validate a catalog of competences, an educational program and didactical materials and resources to deliver both e-learning and face to face continuous training on Simulation Technologies based on Numerical Analysis of Finite Elements (FEM) applied to Hot, Warm and Cold Forging Processes. End users will be both actual and future workers of the industries forging’s sector (technicians and/or engineers), VET Students of Second Cycle of Mechanical Manufacturing Branch and Students of Industrial Engineering willing to become FEM Forging Specialists. According that, 3 courses – basic, intermediate and advanced – will be produced. A research on needed competencies will involve at least 100 forging industries and 5 national associations, who will participate too providing industrial cases studies, validating by tests of evaluation and providing trainees for 6 pilot training experiences, 2 in e-learning delivery. Dissemination activities will involve forging enterprises and be supported by corporate instruments of their national associations.

 Publications

• Kroiß, T.; Engel, U.: Optimization of tool and process design for the cold forging of net-shape parts by simulation. In: Denkena, B.; Hollmann, F. (edtrs): Process Machine Interactions.Heidelberg, New York, London: Springer 2012. 419-438                                                   
• Kroiß, T.; Engel, U.; Merklein, M.: Comprehensive Approach for Process Modeling and Optimization in Cold Forging Considering Interactions between Process, Tool and Press. J. Mater. Process. Technol. 213(2012)7, 1118-1127                                                   
  
  

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Projects

• Closed die precision forging technology to form rocker shaft owing to the complexity of the shaft on structure and process,  Henan University of Science and Technology, China:
  
  According to the Deform-3D simulation of the process, load-stroke curve, law of the metal flow, etc, were acquired, which verified the feasibility and superiority of closed-die forging and was useful to the structural optimization of punch and die subsequently. As for backward extrusion, FE simulation was carried out to study different factors which may have effect on the radial stress towards the inner wall of die. As a result, it was found that properties of extruded material have the strongest effect on the inner wall of die, while the aspect ratio has the weakest.
  
  
• Cold extrusion forming process of internal spline, Chongqing University, China:
  
  After summarizing and analyzing the forming technology of internal spline tooth, the cold extrusion processes were simulated with FE software DEFORM-3D by direct forming and indirect forming. The indirect forming adding a preforming process could mostly improve the production efficiency, the dimension accuracy of the end surface and the die working life. And the optimized process parameters were obtained.
  
  
• Process optimization in cold forging due to oscillating tool movements, Institute for Production Engineering and Forming Machines (PtU) Technical University of Darmstadt, Germany:
  
  A forming failure in conventional forming of longitudinal toothings is buckling due to high forming forces. Using an oscillating ram movement can reduce the required forming force up to 40 %. This leads, amongst others, to an extension of the forming limits and enables e.g. the forming of toothings with smaller wall thickness. The reason for the reduction of the forming force is not clarified yet. Two theories are encountered in literature: One is the “friction theory” which attributes the force reduction to the rebuilding of the lubricating film during the back stroke. On the other hand the “softening theory” attributes the force reduction to softening effects like the Bauschinger-Effect due to the alternating load when using oscillating ram motion. Therefore the two theories are investigated experimentally und numerically. The friction theory is identified as the main factor for the force reduction and implemented in commercial FE-Software systems by using different friction models as well as different friction coefficients. (Contact: Dipl.-Ing. Benjamin Heß)
  
  
• MicrOmega - Precision mechanics: development of an innovative technology for production, through micro-forming of components characterised by complex geometry and high level of dimensional accuracy, in collaboration with Officine Meccaniche OMEGA (2005-2009), Italy:
  
  The project aimed at developing a virtual environment based on FEM simulation tools in order to design cold forging operations of mini-components for automotive industry.
  
  
• Maiatz - Maiatz Simulform (2008-2010), Italy:
  
  The project consists in the transference of the results of research activities carried out in the domain of engineering and university in the project Virtual Intelligent Forging – CA supported by EU Sixth Framework Programme focused in the creation of a knowledge community in forging production technologies. The results of VIF CA that are applied and adapted to develop the main product of MAIATZ SIMULFORM: and specific training program on “Numerical 3D Simulation Technologies on Cold Forming Process”, supported by IT didactical materials. It is oriented to: VET trainees and Workers of Metal Mechanic Branch, and Unemployed workers willing to improve their employability in this Labour Market.

Publications

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