No need to touch with new metal forming technique

A novel way of forming metal, even inside a sealed glass envelope, opens up exciting possibilities in terms of non-contact applications. Tom Shelley reports

Metal can be laser formed to shape without holding it or touching it using a process of carefully controlled heating to bend sheets and tubes and to form collars and ridges, even inside a sealed glass envelope. The brainchild of Professor Jacek Maczynski of the Centre of Metal Laser Technologies, which is part of the Kielce University of Technology in Poland, the process was described by him at a recent Polish Science and Technology Forum organised by the Department of Trade and Industry. Professor Maczynski says he is able to model the process because he studied fluid mechanics “early in life” and hit upon the idea of using dimensionless parameters, such as the ratio of the heat supplied by the beam to the heat lost laterally in the metal. This allows modelling of a process so complex that it lies beyond the capabilities of conventional finite element analysis running on even the most modern PC. In effect, the model has to take account of the parameters of the laser beam, the geometry of the workpiece and its material as well as the effects of temperature gradients, residual stresses, and buckling and upsetting. Having perfected the modelling technique, it is possible to direct the laser beam in such a way as to bend a copper tube or a piece of flat sheet in a very exact manner, counteracting any possible tendency to distort in unwanted directions. However, an absorbing coating is necessary to absorb beam heat and mild steel apparently works best, because of the large difference between its softening and melting temperatures. It has so far been applied to steel sheets from 8 to 20mm thick and metal tubes between 2 and 4mm thick. Laser power available in the laboratory is up to 6kW. The first commercial application is in the modification of electrodes and their supports inside large vacuum tube devices. But the process is not particularly expensive, and it is described it as appropriate for simple tasks such as removing dents from car wings and doors. That said, pipes are apparently more difficult to bend than flat sheets, although the process has been applied to copper pipes and, to quote Professor Maczynski, “if copper works, anything can be made to work.” It became apparent at the meeting that the same process has been independently developed and researched at the University of Liverpool, although the team there seems to be working more on the experimental side. For his part Professor Maczynski has since successfully applied his method to calculating the thermal effect of propagating underground fires. Prof Jacek Maczynski By using novel modelling techniques, it is possible to use laser beams to form metal without touching it The process has successfully been demonstrated on both sheet and tube, and has been used to produce controlled bending as well as forming ridges and flats It works particularly well with mild steel but can be applied to most metals and alloys