No abstract

The production of car body panels are defective in succession of process fluctuations. Thus the produced car body panel can be precise or damaged. To reduce the error rate, an intelligent deep drawing tool was developed at the Fraunhofer Institute for Machine Tools and Forming Technology IWU in cooperation with Audi and Volkswagen. Mechatronic components in a closed-loop control is the main differentiating factor between an intelligent and a conventional deep drawing tool. In correlation with sensors for process monitoring, the intelligent tool consists of piezoelectric actuators to actuate the deep drawing process. By enabling the usage of sensors and actuators at the die, the forming tool transform to a smart structure. The interface between sensors and actuators will be realized with a closed-loop control. The content of this research will present the experimental results with the piezoelectric actuator. For the analysis a production-oriented forming tool with all automotive requirements were used. The disposed actuators are monolithic multilayer actuators of the piezo injector system. In order to achieve required force, the actuators are combined in a cluster. The cluster is redundant and economical. In addition to the detailed assembly structures, this research will highlight intensive analysis with the intelligent deep drawing tool

Tool making is a very time consuming and expensive operation because many iteration loops are used to manually adjust tool components during the try-out process. That means that trying out deep drawing tools is 30% of the total costs. This is the reason why an active deep drawing tool was developed at the Fraunhofer Institute for Machine Tools and Forming Technology IWU in cooperation with Audi and Volkswagen to reduce the costs and production rates. The main difference between the active and conventional deep drawing tools is using piezoelectric actuators to control the forming process. The active tool idea, which is the main subject of this research, will be presented as well as the findings of experiments with the custom-built deep drawing tool. This experimental tool was designed according to production requirements and has been equipped with piezoelectric actuators that allow active pressure distribution on the sheet metal flange. The disposed piezoelectric elements are similar to those being used in piezo injector systems for modern diesel engines. In order to achieve the required force, the actuators are combined in a cluster that is embedded in the die of the deep drawing tool. One main objective of this work, i.e. reducing the time-consuming try-out-period, has been achieved with the experimental tool which means that the actuators were used to set static pressure distribution between the blankholder and die. We will present the findings of our analysis and the advantages of the active system over a conventional deep drawing tool. In addition to the ability of changing the static pressure distribution, the piezoelectric actuator can also be used to generate a dynamic pressure distribution during the forming process. As a result the active tool has the potential to expand the forming constraints to make it possible to manage forming restrictions caused by light weight materials in future

The manufacturing of automotive body components in press lines is a sensitive process. The quality characteristics of body components vary. These fluctuations are rooted in the fact that the factors influencing the component quality are varying, e.g., fluctuations of batches regarding material quality, abrasion or heating of the tool during the production cycle. If a certain quality characteristic exceeds a predefined range an intervention in the process is necessary. This intervention is based upon the subjective know-how of the machine operator. Objective information about the state of the process, like tool temperature or the material quality of the semi-finished product is not available. Therefore, a lack of knowledge emerges in the interrelations between the tuning parameters of the system press-tool and the component quality during different stages of the process (material quality, temperature…). In this paper a complete concept for an automatic process control in press shops is described. The concept will be realized in a pilot plant for mass production in the press shop of AUDI AG. The mechanisms of occurrence of quality defects are shown in the paper, as well as the essential factors influencing the quality during the mass production of body components in the automotive industry and their variation. A sensor-system for continuous measurement of influencing variables during the mass production is presented. The key element of the concept is the non-destructive identification of material-properties for every single blank. By associating the sensor-data with the respective quality, a knowledge-based process control can be realized. The purpose is to create a failure prediction algorithm and make optimal adjustments for each stroke of the moulding press, respectively. The potential of existing actuators in modern press lines as well as new, tool integrated proposals for actuators are highlighted.