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Technical Paper

3-Dimensional Description of Sheet Metal Surfaces

During sheet metal forming processes, the friction conditions have a decisive influence on forming limits, the robustness of the production process and the quality of the parts produced, with significant forces required to overcome friction between the sheet and the tools. If lot-to-lot reproducibility is to be guaranteed, an appropriate method of characterizing the sheet surface topography is needed to monitor the sheet metal fabrication process. Newly developed optical measurement techniques and computer workstation technology are presented which enable the topography of sheet surfaces to be described in three dimensions.
Technical Paper

Combination of Hydraulic Multipoint Cushion System and Segment-Elastic Blankholders

The costs for development and production of draw dies for car outer panels are extremely high and should be reduced. Furthermore it is necessary to reduce the time for developing, designing and producing the dies for the production of parts. This paper discusses new press techniques, die designs and an adjustment program for press operators. The trend goes to single action presses with CNC-controlled multipoint cushion systems in the press table and to special designed dies. These systems lead to a more robust and reproducible forming process with improved product quality. This paper deals with: Cushion Systems, New Binder Designs for Draw Dies for Sheet Metal Automotive Parts, New Computer Program to Adjust the Blankholder Forces of Modern Hydraulic Cushion Systems of Single Action Presses and Pressure Measurement for Detecting the Pressure between the Blank and the Binders of Draw Dies for Sheet Metal Automotive Parts.
Technical Paper

Fundamental Research and Draw Die Concepts for Deep Drawing of Tailored Blanks

According to the present state of knowledge, the use of “Tailored Blanks” with different sheet thicknesses and/or grades represents an interesting manufacturing alternative in the design and development of sheet metal parts in the automotive industry. In order to assess the forming behavior, fundamental research was conducted on laser and mash seam welded blanks. Based on this experimental findings, a segmented draw die was designed and built to determine the limits of the metal forming process by deep drawing of car body parts. The results with this draw die showed that a uniform blankholder pressure must be guaranteed during the forming process in the flange region of the part. This necessitated definite slots in the region of the weld line for the mash seam welded blanks. Furthermore, a die concept was presented to enable an equalization of both sheet thickness steps and sheet thickness fluctuations, without requiring replacement of the respective draw die components.
Technical Paper

New Machine Concept for Hydroforming Tubes and Extrusions, Part 2

In cooperation with industrial companies at the Institute for Metal Forming Technology (IFU) of the University of Stuttgart, Germany, a new press concept specially for hydroforming tubes and extrusions was developed. The press has a capacity of 3500 tons closing force and a press table size of 2500 mm × 900 mm. A great reduction in costs can be achieved by integrating spacers between the frame of the press and the ram. This paper introduces this new press.
Technical Paper

Pulsating Blankholder Technology

In this paper the effects of pulsating blankholder forces in deep draw processes for sheet metal parts are discussed. Areas with and without tangential compressive stresses in the flanges, which are located between the binders, are discussed separately. Areas without tangential compressive stresses can be simulated by a special friction strip-draw test using a pulsating normal force ( representing the blankholder force ). Investigations using this equipment show that by pulsating blankholder forces it is possible to avoid galling and to reduce the friction force. Areas with tangential compressive stresses can be simulated by deep drawing axissymmetric cups using a pulsating blankholder force. Investigations with this equipment show that without increasing the danger of wrinkling the friction forces can be reduced by pulsating blankholder forces, when a certain frequency limit is reached.
Technical Paper

Thixoforming Of Aluminum

Thixoforming is another word for Semi-Solid-Metalforming (SSM) which means that metal will be formed between solid and liquid temperature. In this state the material behavior is thixotropic. Aluminum alloys can be formed in this thixotropic state when 30 to 40% of the material is liquid. In this case it is possible to form the aluminum in a process that is located between the die-casting and the forging technology. The thixoforming process allows it to produce Near Net Shape aluminum-parts with high quality for the automotive industry. This paper is intended to give the reader some examples about and some insights into the possible applications of the thixoforming process.