Design and Adaptation of EMF Equipment

Since the electromagnetic forming (EMF) becomes more and more accepted within industrial manufacturing, the methods engineer has to deal with the choice of matching equipment as to perform the task of production in the best possible way. At the present time several manufacturers offer EMF-machines with different characteristics, whereby the machines consist of a pulse power generator and an exchangeable tool coil. The storable energy, the current capability and a high short circuit frequency enable the engineer to adapt tool coils for an optimised pressure course. In the following some aspects of how to dimension direct acting tool coil properties for the EM compression process will be considered. Basically the use of multi-turn coils is advantageous for a good matching. But in a lot of cases the use of a fieldshaper is necessary. It will be shown how the design of a tool coil system including a fieldshaper influences the pressure course. A special case is the application of EM compression in closed spaceframe structures for which a separable tool coil is required. A separable compression coil with non-welding contact elements will be presented

Impulse Hydroforming Method for Very Thin Sheets from Metallic or Hybrid Materials

Forming of very thin metallic and hybrid material foils is a demanding task in several application areas as for example in food or pharmaceutical packaging industries. Narrow forming limits of very thin sheet metals as well as minor process reliability due to necessary exact tool manufacturing (small punch-die clearance), both, causes abiding interest in new and innovative forming processes. In this contribution a new method using high pressure pulses will be introduced to form small geometry elements into very thin metal foils or into hybrid polymer-metal foil. It will be shown how the acting pressure pulse will be generated by electromagnetic acceleration of a certain mass, which initiates a pressure wave within a working media. The effect of different pulse lengths has been compared and evaluated by the forming result. Finally, an outlook concerning suitable pulse power equipment and its industrial capability will be given

Investigation of the Electrohydraulic Forming Process with respect to the Design of Sharp Edged Contours

The overcoming of design constraints with respect to forming of sharply contoured sheet metal workpieces made of high strength steel or other materials which are difficult to form is an important aspect in sheet metal part production. One interesting solution to extend existing forming limits can be the use of electrohydraulic forming as single forming operation or in combination with quasi-static hydroforming. Apart from promising results regarding the feasible part geometries this process allows a quite efficient production due to its potential to reduce equipment expenses. Current research work at the Chair of Forming and Machining Technology (LUF) at Paderborn University deals with a comparison of investigations on both processes, quasistatic and high speed hydroforming. Recent results show an adequate comparison of achievable edge radii using an oblong die geometry and sheet metal made of thin stainless steel. It can be seen that when using electrohydraulic forming an increase of discharge energy leads to smaller radii than achievable by quasi-static hydroforming. An additional potential can be seen in the process characteristic itself because the very short pressure pulse allows a significant reduction of locking forces using only the inertia of the tooling mass

Investigation of the Process Chain Bending-Electromagnetic compression-Hydroforming on the Basis of an Industrial Demonstrator Part

The increasing significance of lightweight construction concepts requires innovative and adapted production technologies and process chains for the manufacturing of complex parts made of typical lightweight materials. The feasibility and potential of such a process chain consisting of the steps Bending - Electromagnetic compression (EMC) Hydroforming is shown in the present paper on the basis of a demonstrator part similar to a structural component from the automotive industry. Here, special focus is put on the requirements on the production steps and the workpiece properties. Furthermore, the development and testing of EMC-equipment that is optimally adapted to the special forming task is described

On the Significance of the Die Design for Electromagnetic Sheet Metal Forming

Electromagnetic Forming is a high speed forming process using a pulsed magnetic field to form metals with high electrical conductivity, such as copper or aluminium alloys. During the process, typical pressure peaks up to 200 MPa and velocities in the range of 300 m/s can be achieved. As significant process parameters the pressure maximum as well as the local and temporal varying pressure distribution have been identified. As of a certain drawing depth and distance between workpiece and tool coil, the pressure does not act any longer on the workpiece, but the deformation process is still driven by the inertia forces. It has been found out that the velocity distribution within the sheet metal during the forming stages as well as at the time of impact with a die significantly influences the forming result. Additionally, a special undesired effect is the rebound behaviour of flat workpiece areas being in contact with the die. To investigate the influence capability of the die concerning this effect, the parameters stiffness and damping properties have been varied by means of simulation using a mechanical substitute model

Aspects of Die Design for the Electromagnetic Sheet Metal Forming Process

Within the electromagnetic sheet metal forming process, workpiece velocities of more than 300m/s can occur, causing typical effects when forming into a die, which will be described and discussed in the present paper. These effects make numerous demands regarding the die design. In order to analyze these requirements, experimental as well as numerical investigations have been carried out. Thereby, special focus is put on the possibilities to accomplish these requirements, which are discussed in the following

Process Investigation of Tube Expansion by Gas Detonation

The present paper deals with the expansion of tubes by direct application of gas detonation waves, i.e. the gas is both pressure medium and energy source. After an introduction to gas detonation forming, measurements of the motion process and the internal pressures are presented. Results of free expansion and of forming into a die are thoroughly studied and compared to the results of quasi-static burst tests and hydroforming. Using pure aluminum Al99.5 and a medium strength alloy AlMgSi1, expansions by 25 % and 20 % respectively are obtained. A simulation delivers details on the deformation process and specially prepared probes of high-speed tension tests give new insight into metallographic material behavior at different strain rates

Design and Analysis of a Deep Drawing and Inprocess Electromagnetic Sheet Metal Forming Process

The design as well as the subsequent analysis of a deep drawing and in-process electromagnetic sheet metal forming calibration will be described in this paper. Due to the quite different forming processes concerning the occurred strain rates, an investigation on the microstructure of the formed workpieces will be pointed out. Furthermore, the design steps regarding the integrated tool coil will be presented and the resulting examples discussed. Finally, the setup of the integrated process as well as the feasibility will be shown on an exemplary semi-industrial workpiece