Fraunhofer IWU Research Articles

Development of a suction gripper network based on the biological role model of an octopus

The handling of fragile, sensitive or flexible components in assembly technology and production requires grippers that are designed for gentle handling of the objects to be gripped. Suction grippers are still a widespread standard solution for this purpose. However, rising energy prices are making pneumatic grippers, which work with a central upstream compressed air supply, increasingly unattractive. The generation of the compressed air itself, the mostly leaky transmission and the relatively inefficient vacuum generation are cost drivers that many users would like to avoid. Consequently, vacuum-based gripper means are required for industrial production, which work without externally generated compressed air. At the Fraunhofer IWU, a compressed-air-free suction pad composite has been developed that enables gripping of components with a wide variety of shapes. The underlying concept is inspired by the function of the suction arms (tentacles) of an octopus. By evacuating several small volume areas, which can be individually mechanically actuated, safe and sensitive gripping of objects is possible. For the generation of the vacuum, a piston system and a principle of an artificial muscle were developed, which is controlled based on shape memory alloys.

AMARETO – Saxon Alliance for MAterial‐ and Resource‐Efficient TechnOlogies

AMARETO – Saxon Alliance for MAterial‐ and Resource‐Efficient TechnOlogies

Software assisted clamping point classification and position optimization for the efficient flexibilization of carbody fixtures using mathematical geometry-based search algorithms

The Fraunhofer IWU has been developed specialized clamping robots for production of different car-models on one fixture. One of the challenges with universal clamping of different components is the contact point between part and clamping device. For the optimization of the clamping contours, a software was developed with which the geometries of the clamping points can be automatically analyzed and classified. With target search criteria, the clamping position on the component can be changed so that the clamping contours are geometrically simplified. Thus, a huge reduction in the complexity of the flexible clamping device is possible.

Automated design of product-flexible car body fixtures with software-supported part alignment using particle swarm optimization

The Fraunhofer IWU has been developed specialized clamping robots for production of different car-models on one fixture. As a base for the fixture design, a method for optimal part alignment has been developed. For handling multitude of possibilities regarding the alignment of parts from different car-models, a specific software tool using particle swarm optimization has been created. The objective was to achieve similar travels for all clamping robots in this fixture. To facilitate the integration of the automated part alignment into fixture design, a further software tool for automatically designing a flexible fixture was modelled.

Predictive Analysis from numerical and experimental data in press hardening

Machine learning, big data and deep learning are today’s catchphrases for how to improve reliability and productivity of your manufacturing equipment. Production companies implement a large number of sensors to record every activity within their production lines and learn as much as possible about their running processes in order to predict shifting product properties and to prevent stoppage due to failure. The successful application of machine learning algorithms to predict machine and process behavior depends on a reliable and balanced database. Since the foremost goal of every manufacturing business is to make sound parts and to avoid defects, there is a large amount of data available for smoothly running processes but only very little for failure production. One approach to solve this imbalance would be to link the production line data with simulation data. Simulation models allow for computing failure parts with no additional costs and therefore enable the exploration of the entire parameter space. We conducted press-hardening experiments with a variation of process parameters for a structural car body part on the press hardening line at Fraunhofer IWU. As an evaluation criterion, we measured the hardness of the final part at critical spots. In order to expand the experimental data, we applied FE simulations to the entire press hardening process chain. The paper explains limitations of the model and elaborates on its parameterization. As a final task, we applied a basic machine-learning algorithm to both experimental and numerical data as well as to their combination in order to evaluate the data space expansion through simulations. The results obtained through machine learning indicate significant differences in the prediction of part quality for solely experimental data and its combination with simulation data. This is especially true for press hardening because of non-linear system behavior and a large amount of uncertain and hard-to-identify parameters. We found that the most challenging parts of uniting measured and simulated data is not only to create simulations with appropriate accuracy, which allow for a meaningful extrapolation of the parameter space, but also to compare simulation and production data based on the same criterion and to have stable simulation models for the entire parameter range.

Media Based Forming and Injection Molding Based on Fiber Reinforced Plastic Tubes

Abstract Research and development for industrial applications forces Fraunhofer IWU to explore new fields of technology. The combination of Media Based Forming and Injection Molding (MBF-IM) in a single process is such a new development to meet the requirements on lightweight design and resource efficiency. Based on over 20 years of Fraunhofer IWU experience in hydroforming, this technology development started with the usage of metal tubes and PA6 with glass fiber to produce metal-plastic-hybrid-components the structural strength of the component is realized by the formed metal tube while the molded attachment allows for easy functionalization. Cockpit cross beams (CQB) are known state of the art components produced this way. In a first development step the conventional hydroforming process was replaced by media based forming (MBF) using nitrogen as a pressure medium. With this process the tool can always be kept dry for the injection molding (IM) process without any additional effort, and no subsequent part cleaning is necessary. Together with TU Chemnitz and industrial partners further developments are continuously carried out and still under research. The focus of this strategic cooperation is the development and the usage of plastic tubes for the structural function of the component. The paper shows the development path from the state of the art for the MBF-IM from metal-plastic hybrid components to the replacement of the liquid active medium for the MBF by gaseous nitrogen, the use of endless fiber-reinforced plastic tubes as semi-finished products to the MBF-IM of short-fiber-reinforced plastic tubes.

Process simulation and experimental validation of Hot Metal Gas Forming with new press hardening steels

One field in the work of the Fraunhofer Institute for Machine Tools and Forming Technology IWU in Chemnitz is industry applied research in Hot Metal Gas Forming, combined with press hardening in one process step. In this paper the results of investigations on new press hardening steels from SSAB AB (Docol®1800 Bor and Docol®2000 Bor) are presented. Hot tensile tests recorded by the project partner (University of West Bohemia, Faculty of Mechanical Engineering) were used to create a material model for thermo-mechanical forming simulations. For this purpose the provided raw data were converted into flow curve approximations of the real stress-real strain-curves for both materials and afterwards integrated in a LS-DYNA simulation model of Hot Metal Gas Forming with all relevant boundary conditions and sub-stages. Preliminary experimental tests were carried out using a tool at room temperature to permit evaluation of the forming behaviour of Docol 1800 Bor and Docol 2000 Bor tubes as well as validation of the simulation model. Using this demonstrator geometry (outer diameter 57 mm, tube length 300 mm, wall thickness 1.5 mm), the intention was to perform a series of tests with different furnace temperatures (from 870 °C to 1035 °C), maximum internal pressures (up to 67 MPa) and pressure build-up rates (up to 40 MPa/s) to evaluate the formability of Docol 1800 Bor and Docol 2000 Bor. Selected demonstrator parts produced in that way were subsequently analysed by wall thickness and hardness measurements. The tests were carried out using the completely modernized Dunkes/AP&T HS3-1500 hydroforming press at the Fraunhofer IWU. In summary, creating a consistent simulation model with all relevant sub-stages was successfully established in LS-DYNA. The computation results show a high correlation with the experimental data regarding the thinning behaviour. The Hot Metal Gas Forming of the demonstrator geometry was successfully established as well. Different hardness values could be achieved depending on the furnace temperatures and the investigated material. Hardness up to 620 HV could be measured on the component with a complete martensitic structure.

Developing and Harnessing the Potential of SMEs for Eco-efficient Flexible Production

Production-oriented ICT solutions, offering an intelligent networking of value adding systems, which are interconnected and able to communicate with each other and with the Internet, are seen as key enablers for next generation production systems in “Industry 4.0” scenarios. These future manufacturing systems will be more energy efficient, saving limited resources and having a minimized negative impact on the environment. They also will be able to adapt to new requirements and conditions, incorporating and harnessing human flexibility, creativity and problem-solving capabilities. That's why, apart from ready-to-use technical systems and adequate organizational structure, competent employees, qualified to interact with and to make use of those technologies are of major importance for the success of “Industry 4.0”. Especially SMEs with limited R&D capabilities have to overcome significant obstacles in order to implement the elements mentioned above. The paper introduces the “E3ResearchFactory” located at Fraunhofer IWU in Chemnitz and demonstrates on several examples, which specific solutions and use cases are developed and transferred towards small and medium-sized production companies.

Hot Rolling of Large Gears

Forming processes are generally characterized by a high degree of material utilization as well as short process times and, consequently, a decent economic efficiency. Furthermore, incremental forming enables the use of relatively low forming forces which results in a more compact design of the used machines. These conveniences are utilized in terms of roll forming with round tools to form gears and threads in a competitive way. Based on experiences gained over many years of researching rolling technologies, a cross-rolling process characterized by round tools with outer gearings was elaborated to realize a hot forming process of large gears at the Fraunhofer IWU. At actual project GEARFORM, a scaled sun gear demonstrator from wind gear application could be realized by hot rolling technology. An optimized rolling time was achieved by 32.5 seconds.

Automatic Adjustment of Car Body Fixtures Using Artificial Intelligence

In car-body production, the fixtures used for fixing the car-body panels during the joining pro-cesses predominantly consist of rigid constructions that require a time-consuming manual set-up process. To automate the adjustment process and reduce ramp up times, different adjustment modules have been developed at the Fraunhofer IWU in order to meet specific requirements. Because of high quality requirements, produced components will be checked against an adjustment database. The exactly positioning for each clamping point will be derived, with the aid of mathematical algorithms and modern methods of artificial intelligence, based on measured values and the knowledge of the template technicians.

Hot forming of large spur gears

Forming processes are generally characterized by a high degree of material utilization as well as short process times and, consequently, a decent economic efficiency. Considering their application in the manufacturing of large spur gears, forming processes offer a significantly attractive characteristic for the production of essential gearing components commonly used in wind turbines or marine engines. Furthermore, the hot forming process can be defined as an incremental forming process which enables the use of relatively low forming forces and results in a more compact design of the used machines. These conveniences are utilized in terms of roll forming with round tools to form gears and threads in a competitive way. Based on experiences gained over many years of researching rolling technologies, a cross-rolling process characterized by round tools with outer gearings was elaborated to realize a hot forming process for gear rolling of large spur gears at the Fraunhofer IWU Chemnitz. Based on the already researched forming of smaller dimensioned gears, rolling trials utilizing a new hot-forming machinery - including defined inductive heating process before rolling - to realize large gears with outer diameters of up to 1000 millimeters were conducted. In terms of realizing this ambition, the derivation of the designated machine parameters for rolling large gears in real-life dimensions can be defined as a crucial factor. Consequently, the experimental research was followed by a mathematical analyzation of the forming forces, momenta as well as the necessary steps to determine the best possible scaling factors for the work pieces.

Resource Networks: Decentralised Factory Operation Utilising Renewable Energy Sources

Striving for sustainability, most industrialised countries make increasing use of renewable energy sources to meet their energy demands. This causes power generation to become more decentralised and volatile, making flexibility in production (i.e. energy demand) a fundamental necessity for manufacturing companies. Hence, it is to be expected that companies which attain a symbiosis of renewable energy applications, efficient technologies, and innovative approaches to production organisation will have a competitive advantage in the future. The EU funds research in this direction as part of the REEMAIN project, amongst others. In particular, a concept for Resource Networks is developed. These networks aim to manage production using renewable energy sources by dividing a complex factory into smaller subsystems including energy suppliers and consumers, as well as storages to reach this symbiosis. This paper explains the concept and its application within Fraunhofer IWU's E3-Research Factory.

High Performance of Machining Processes by Applying Adaptronic Systems

Manufacturing processes are constantly facing the demand for higher efficiency regarding time, costs and resource consumption. In addition, challenges arise from the use of new materials and stricter requirements concerning the efficiency of the final product in use. Besides the economic perspective of realizing a highly efficient production and sustainable products, a new level of standards is set by politics and industry. To meet these demands, it may no longer suffice to improve processes by optimizing process parameters. Instead, advanced machine and tool concepts will be necessary and therefore have to be developed. An innovative approach to enhance the cutting process is the integration of adaptronic systems. This integration can happen at different levels, from no close loop control to using additional feed drives and in the cutting tool or in the machine. The paper presents examples from research at Fraunhofer IWU for the application of adaptronic systems in machining processes, such as ultrasonic assisted machining, adaptronic form honing and adaptive spindle support for precision finishing of cylinder bores. Properties of the actuators and the adaptronic systems are described and the effects on both, the efficiency of the machining process and the final product performance, are discussed.

New methods for more accurate material characterization

In order to ensure better process design and tool optimization, it makes sense to describe material behavior in the context of phenomenological plasto-mechanics. To achieve this, it will be necessary to determine material behavior comprehensively and also to a high level of precision, in order to determine accurately the start of flow and to put forward specific variables relative to the forming process. At Fraunhofer IWU these endeavors have been expanded to form a main research area, with the aim, for example, of making the necessary material variables available under actual process conditions, detailed and accurate, for a range of different simulation programs.