Search Results

Deep drawing with hydraulic counter pressure has numerous advantages compared to conventional deep drawing. Hydromechanical deep drawing is a capable process for producing complex and tapered-shaped stamping parts as well as parts with excellent surface quality, i.e., outer body panels. Due to the low costs of dies, compared to the conventional deep drawing dies, hydromechanical deep drawing has to be considered especially for low volume production. This paper deals with press- and die concepts for hydromechanical deep drawing. The die concepts can be equipped with an integrated multi-point cushion system. It is also possible to build a press with a multipoint cushion system integrated into the press. In this case, the die is less expensive but the press is more complex. The counter pressure pot can be product specific as a part of the die or as a part of the press investment.

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.

By inner pressure hydroforming a great variety of parts can be produced. This is especially true when forming tubes in a single action press with high closing forces. In cooperation with industrial companies at the Institute for Metal Forming Technology of the University of Stuttgart, Germany, a new concept for presses specially designed for hydroforming tubes and extrusions was developed. The press has a capacity of a 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 and discusses different press concepts for hydroforming tubes and extrusions.

This paper deals with the radii of draw dies for sheet metal parts, like fenders, hoods, and doors. For relative flat parts, like hoods, it is important to get at least a 2% forming rate in the middle of the part to reach minimum of stiffness, work hardening, and sufficient geometric accuracy. This can be influenced by the punch radii. Therefore, optimal punch radii should be known. First experimental results about optimal punch radii where published by J.L. Duncan and B.S. Shabel in the SAE-Paper No. 780391. At the Institute for Metal Forming Technology of the University of Stuttgart, Germany, a “Modified Duncan Shabel Test” (MDS-Test) has been developed. This test makes it possible to investigate not only the punch radii but also the die radii. This paper shows optimal punch and die radii as a function of sheet metal, sheet thickness, as well as of the die material.

State of the art is the CAD-development of personal cars. But as before it seems to be necessary to build up prototype dies for producing sheet metal prototype parts. Outgoing from the CAD-design of the sheet metal auto-body parts it is possible to design prototype dies using CAD, to produce patterns and dies using CAM and to stamp sheet metal prototype parts. So we get prototype parts for testing stiffness, crash behavior etc. and we get with prototype dies the possibility to test and to optimize the binder design of a draw die. The proven optimized binder design of a prototype draw die can be taken over to the design of the final production die. This paper deals with prototype die materials and with the criteria of the material selection.

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.

In sheet metal stamping some industrial applications have shown that it is possible to achieve larger drawn depth by using a pulsating blankholder force. In deep drawing, areas with and without tangential stresses have to be distinguished. Areas without tangential stresses can be described by the strip drawing test. Areas with tangential stresses are described by using a deep drawing die for the production of cups which are axisymmetric. With the strip drawing test it could be shown that it is possible to reduce the increase of the friction force, caused by adhesion. Another effect is the reduction of the peak of the transition of static to dynamic friction. It was shown by experimental research, that the wrinkle height of parts, produced with pulsating blankholder force is in the range of the wrinkle height of parts produced with a constant blankholder force which is equal to the maximum force of the pulsation.

The objective of this paper is to introduce a method for producing effective binder designs for sheet metal forming of automotive body panels. The fundamentals steps of die design are discussed as well as methods for checking the developability of binder surfaces and the application of a binder simulator and FEM process simulation. A front fender and a door panel have been used to illustrate the methodology.

When drawing non-axissymmetric sheet metal parts it is necessary to control the flow of material between the lower and upper binder in such a manner that prevents the occurrence of both tears and wrinkles in the drawn part. One possibility for the control of the material flow is through the deliberate adjustment of the normal forces. If one can measure the flow-in of the material into the die cavity as a function of punch stroke with a special sensor, and if this information can be used to produce an empirical flow-in curve over the stroke for good parts, then it is possible to construct a closed- loop BHF control system. Building such control system is feasible by implementation of special dies with hydraulically supported segmented binders. This system allows an automatic response to a change in the friction conditions.