Point of view

Combination Machine, yes or no?

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The sheet metal working sector is very wide and as numerous are the typologies of machines and equipment used. They often highly differ one another, I think that a forming line and a nibbling machine have little, not to say nothing, in common indeed! Nevertheless, there are technological development issues, which in general concern the whole mechanical engineering, shared by all productive resources used in our sector. As already said several times, among them we can find the trend to integrate more and more the machine into the system, offering complete solutions: loading/unloading automation, “dialogue” possibilities with other units, tele-service capabilities and so on. Another, mainly connected with the demand of producing increasingly small batches, is represented by the increase of flexibility. With this term, we mean several characteristics of both the single unit and of the entire productive department. There are various aspects, as important, linked with the machine, the process, the production volume, the product, the cycle, the system expansion and so on. Actually, the goal would be that the single productive unit could machine cost –effectively the biggest possible deal of product typologies in smaller and smaller batches (even one-off). From a merely technological point of view, a significant example of flexibility increment is represented by combination units. Undoubtedly, relying at the same time on the operating capability of the punching machine and of the LASER machine enormously increases the range of different workpieces that it is possible to machine, combining the speed of the punching machine with the great variety of patterns that LASER allows implementing. However, to the ends of real flexibility, economic convenience is needed in addition to technological skills. In other words: a machine can be technically able to machine various different parts but it takes a lot of time (and cost) to changeover from one to the other, in this case it becomes advantageous to machine enormous batches, even always producing the same piece. Certainly, we cannot define this unit flexible! A possible approach is suggested by the “Single Minute Exchange of Die (SMED)” methodology: one of the pillars of the lean production, it was conceived in Japan just to reduce the die change time on presses for sheet metal working. Decreasing setup costs, besides several other benefits, we also make the operation with smaller and smaller batches advantageous in economic terms and then we increase the machine flexibility (also from an economic point of view). It is worth underlining that this strategy is generally pursued for all machine typologies used in our sector: from the nibbling machine to the forming line. A flexibility less taken into account concerns raw materials. As all sector players know, sheet metal is never the same! Even complying with the limits of the reference regulations, the thickness, the material quality, the surface finish and so on can vary from one supply to the other. We all know that very small variations in these parameters lead to notable variations in the quality of the finished product due, for instance, to the different spring-back in the free air bending. Concerning this, adaptive controls that, in the above mentioned example, modify the stroke of the press brake according to the actual thickness of the sheet-steel and the material characteristics, significantly increase the flexibility of the operating unit, making it unaffected (within obvious limits) by the characteristics of raw materials. We can therefore buy with a more serene state of mind”. I expect then, for the machine tools that we will use in the future, a strong trend towards automation, integration and flexibility. Easy to say, perhaps also to do if we pursue only one of these goals, much more difficult if we really want to attain all of them simultaneously!