Hybrid processes in manufacturing

Considerable changes have occurred in metal forming in the last decade. A record of these changes can be found in keynote papers presented by the members of the Scientific Technical Committee—Forming, at the CIRP Annual General Meeting each year. The keynote papers are excellent references on important developments in metal forming and are used as a reference, globally. Not only is this paper a compendium of most of the keynotes presented, but from 2001 onward, it has updates on new information on five keynote subject areas. The authors of each keynote have written an update with new information that has developed since the writing of the keynote. The authors of each section are shown in order of presentation.

Metal forming progress since 2000

Today, hybrid manufacturing technology has drawn significant interests from both academia and industry due to the capability to make products in a more efficient and productive way. Although there is no specific consensus on the definition of the term ‘hybrid processes’, researchers have explored a number of approaches to combine different manufacturing processes with the similar objectives of improving surface integrity, increasing material removal rate, reducing tool wear, reducing production time and extending application areas. Thus, hybrid processes open up new opportunities and applications for manufacturing various components which are not able to be produced economically by processes on their own. This review paper starts with the classification of current manufacturing processes based on processes being defined as additive, subtractive, transformative, joining and dividing. Definitions of hybrid processes from other researchers in the literature are then introduced. The major part of this paper reviews existing hybrid processes reported over the past two decades. Finally, this paper attempts to propose possible definitions of hybrid processes along with the authors’ classification, followed by discussion of their developments, limitations and future research needs.

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A review of hybrid manufacturing processes – state of the art and future perspectives

In the current work, a new method is proposed for hot incremental forming. The method is based on simple tooling and is easy to employ. It makes use of electric current for heating hard-to-form sheet metals at the tool–sheet interface in order to fully utilize the formability of these materials. The potential effect of processing parameters, namely current, tool size, feed rate and step size, on the formability are investigated using AZ31 magnesium. In addition to this, the shape distortion of TiAl2Mn1.5 titanium workpiece after hot forming has also been addressed herein. Experimental results demonstrate that this technique is feasible and easy to control.

Electric hot incremental forming: A novel technique

A review on forming techniques for manufacturing lightweight complex—shaped aluminium panel components

Laser Assisted Incremental Forming: Formability and Accuracy Improvement

The limited accuracy of the single point incremental forming process [J. Jeswiet, F. Micari, G. Hirt, A. Bramley, J. Duflou, J. Allwood, Asymmetric single point incremental forming of sheet metal, Annals of CIRP 54(2) (2005) 623–650] has been identified as its major deficiency [J.M. Allwood, G.F. King, J. Duflou, A structured search for applications of the Incremental Sheet Forming process by product segmentation, Proceedings of the Institute of Mechanical Engineers, Part B, Journal of Engineering Manufacture 219(2) (2005) 239–244]. Improving the process by introducing either fixed [J.R. Duflou, B. Lauwers, J. Verbert, F. Gelaude, Y. Tunckol, Medical application of single point incremental forming: cranial plate manufacturing, in: Proceedings of the VRAP 2006 Conference, Leiria, September 2006, pp. 161–166] or programmable support structures [J.M. Allwood, N.E. Houghton, K.P. Jackson, The design of an incremental sheet forming machine, in: Proceedings of the Shemet 2005 Conference, Erlangen, April 2005, pp. 471–478; H. Meier, O. Dewald, J. Zhang, incremental forming of sheet metal by two industrial robots, in: AMST’05 Advanced Manufacturing Systems and Technology 2005, vol. 486, Springer, Wien, New York, pp. 437–444], tends to reduce the flexibility of the process and increases the complexity of the control system. In the presented research, the authors have opted for an alternative approach in which the material properties are differentiated by localised temperature variations. In this way, different zones can be created in the sheet metal part being processed. By means of a dynamic heat, input in the direct vicinity of the stylus, a ductile area with low-yield strength is generated. By synchronising the movement of the heat source over the sheet metal surface with the stylus feed rate and direction, and by using appropriate cooling of the surrounding area, a temperature gradient can be assured between this area and the workpiece zone where no deformation is envisaged. Effects of such strategy are reduced forces on the stylus and, in consequence, a better localised deformation and thus a higher precision. Furthermore, higher forming limit angles have been demonstrated for materials with low strainability at room temperature. An experimental setup has been built to test this dynamic, local heating principle and is described in the paper. The effects on the process performance are demonstrated by means of experimental results.

Improved SPIF performance through dynamic local heating

The present invention relates, in general, to sheet material forming technology and the forming of structures there from. The invention relates to incremental forming of sheet material (1) with localised heating (5) and more particularly to a system and method for incrementally forming a sheet blank (1) that is at the same time heated by a dynamically moving heating source (5). This dynamic and localised heating locally changes the mechanical properties of the sheet material (1), thus facilitating the forming process.

Asymmetric incremental sheet forming system

Laser forming of sheet material has been widely investigated for the last 15 years. While researchers encounter severe problems during the forming of a 3D free form shape, at least one category of surfaces can be made with the process of laser forming, namely the developable surfaces, which are widely used in, for example, ship building. Those surfaces show a zero gaussian curvature and can be unrolled onto a plane without distortion. Until now, the forming of such surfaces has been more or less heuristic, but this paper aims to treat the CAD/CAM issues of this problem in a generic way. Once the surface has been defined, in order to obtain a developable surface, the surface is rebuilt into a number of planar flanges. After collision testing, the unfolding of the surface is calculated. The developable surface is scanned on the boundary between two flanges using laser settings that are determined based on efficiency optimisation considerations, keeping in mind the hardware limitations and the possible surface damage for a too high input energy. In this paper, the proposed CAD/CAM procedure is validated by means of a developable parabolic cylinder.

Laser Forming Oriented CAD/CAM for Developable Surfaces

The aim of the research presented in this paper is to investigate the feasibility of generating 3D features in sheet metal blanks using laser forming techniques. Aiming for systematic process planning and a good process control capability, only the temperature gradient mechanism is considered for this purpose. The research has been performed on a 6 kW CO2 laser CNC platform. In a first part, bending along curved lines and bending close to edges are investigated. In a second part, these findings are applied for the creation of a louver. A dimensional measurement system is used for analyzing the geometric dimensional characteristics of the formed shapes. It is found that louvers can be made as a local 3D feature in a sheet metal blank. Based on these initial results, it can be concluded that form features, which are traditionally generated by means of form tools on a punching machine, can to some extend also be obtained by means of industrial lasers, widening the application range of these machine tools.

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Bart Callebaut

Papers

Laser Assisted Incremental Forming: Formability and Accuracy Improvement

Improved SPIF performance through dynamic local heating

Asymmetric incremental sheet forming system

Laser Forming Oriented CAD/CAM for Developable Surfaces

Laserforming of 3D Features