Flexible forming with hexapods

Hesselbach, Jürgen; Behrens, Bernd‐Arno; Dietrich, Franz; Rathmann, Sven; Poelmeyer, Jens

doi:10.1007/s11740-007-0063-3

Cited by 11 publications

(6 citation statements)

References 5 publications

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“…The process is enhanced to manufacture non rotary parts on the punch facing side and thereby expand the design freedom for orbital forming [4]. Multi-axis forming shares the local contact area between workpieces and punch while having more design freedom regarding the punch trajectory [2]. To achieve the correct part geometry, the punch geometry is a result of the punch trajectory and part geometry.…”

Section: R Relat Elated W Ed Wor Ork Kmentioning

confidence: 99%

Directing the Material Flow and Form Filling through a Multi-axis Forming Process

Wonnenberg¹,

Gabriel²,

Dröder³

2021

Esaform 2021

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Multi-axis forming is a six degree of freedom forming process. This process influences actively the material flow by defining a six dimensional tool motion path and the corresponding tool velocity. Within this process, it is possible to combine a linear forming movement followed by a rolling movement and therefore tailor the induced local material properties of the work piece. The research objective of this work is to observe and quantify the interaction between tool motion and material flow for the purpose of process planning. Experiments are conducted to examine the horizontal material flow within a multi-axis forming process of a plane L-shaped work piece. Three different punches form the material: Flat, cylindrical and cone-shaped. The horizontal material flow is recorded through a transparent die by a camera to measure the material flow for different tool motions. It is shown, that a multi-axis forming process can adjust the local material flow. The resulting redirection of the material flow after the sharp inward facing edge of the L-shape is analyzed and compared. With a smaller active zone compared to a standard linear pressing, the multi-axis forming forces are reduced. In addition, the reservoir with the remaining material is more concentrated. Finally, it is possible to direct the material flow with the punch motion, which can be used to determine local part properties.

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Section: R Relat Elated W Ed Wor Ork Kmentioning

confidence: 99%

Directing the Material Flow and Form Filling through a Multi-axis Forming Process

Wonnenberg¹,

Gabriel²,

Dröder³

2021

Esaform 2021

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“…For the experimental set-up, a six degree of freedom press, for instance a Stewart platform, realizes the multi-axis forming process. The authors in [19,20] give a description of the press. Figure 2 displays the set-up with six hydraulic cylinders, which are connected to form a parallel kinematic between the frame and a platform that carries the punch.…”

Section: Experimental Set-upmentioning

confidence: 99%

Path velocity planning for a forming process of fiber-reinforced thermoplastic with six degree of freedom

Wonnenberg

Dröder

2021

Prod. Eng. Res. Devel.

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By punch trajectory planning for a multi-axis forming press, it is possible to affect the local material properties in the workpiece. A multi-axis forming process can influence the material flow and thus the material properties via the punch path. During multi-axis forming processes, the velocity on a defined punch path affects the heat transfer between the punch and the forming material. An example for such forming materials is glass mat thermoplastics (GMT). Multi-axis forming can form these materials in a molten state. The materials cool down during forming due to contact-induced heat transfer between material and punch. The contact zone varies during the process and depends on the punch path. The punch velocity, however, influences the duration of the contact. In order to plan the punch velocity for required part properties, this paper presents an analytical model. The model bases on the geometrical description of the contact zone and gives different velocity profiles, which are tested in experiments. Finally, the paper discusses the analytical model, the velocity profiles and the requirements for the press.

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“…63 The ‘HexaBend’ developed at TU Chemnitz is a hydroforming device that can be used to bend tubes and profiles. 64,65 Likewise, the flexible forming machine developed at TU Braunschweig 66 is a hydraulically operated hexapod in which cascaded control with sliding mode is used to account for the uncertainties in the hydraulic actuator model.…”

Section: Modelling Of the Stewart Platformmentioning

confidence: 99%

Force control in a parallel manipulator through virtual foundations

Bera

Bouamama

Samantaray

2012

Proceedings of the Institution of Mechanical Engineers, Part I:

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An overwhelming controller provides robustness against uncertain parameters, disturbances and un-modelled dynamics. A simplified inverse dynamics model is used in the present paper to develop an overwhelming controller for a parallel manipulator (a Stewart platform), where the controller accommodates modelling uncertainties such as the simplifications made for development of the inverse model in order to improve the computational efficiency. Such a control strategy leads to good trajectory tracking accuracy in the presence of unknown disturbances. However, in addition to trajectory tracking performance, the controller for a Stewart platform should also be able to control or limit the interaction forces in applications such as robot assisted surgery and low-impact docking. The environmental forces can be accommodated during the interaction period by modulating the impedance at the interface of manipulator and environment through virtual flexible foundations. The positional error induced during the force control phase can be recovered during the free flight or idle phase. While this approach has been used successfully in the past to control serial manipulators, the closed loop kinematic architecture in a parallel manipulator introduces many difficulties. This paper proposes a modified overwhelming control scheme for parallel manipulators with compensations for interaction force control and positional error recovery. Bond graph modelling is used as an integrated model and controller development tool. Force controlled machining on a spherical surface, which is akin to a surgical operation, is considered as an example application of the developed control strategy. The simulation results from the bond graph model of the controlled Stewart platform are presented to demonstrate the performance of the developed hybrid position force controller.

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Flexible forming with hexapods

Cited by 11 publications

References 5 publications

Directing the Material Flow and Form Filling through a Multi-axis Forming Process

Directing the Material Flow and Form Filling through a Multi-axis Forming Process

Path velocity planning for a forming process of fiber-reinforced thermoplastic with six degree of freedom

Force control in a parallel manipulator through virtual foundations

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