Less is more

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Author: Prof. Dr.-Ing. Peter Puschner,
Welding expert and consultant of ELMA-Tech GmbH

peter puschnerMore force, more current ...

is the widespread opinion in recent decades, when the expected result is not achieved with spot welding.

With the introduction of high-strength steels, this ultimately wrong opinion has initially found a confirmation, if due to fit errors sheet surfaces do not even come to contact at forces below 4 kN. At a first glance, in this case 6 kN and more help, and in fact a tough weld nugget can be produced.

But ...
the components welded in this way are having considerable internal stresses, the sheets, joined under mechanical strain, already load the spot very fast with 50% of its load capacity. But this can not be the last word: on the one hand high and higher strength steels are used for reasons of weight, on the other hand the load capacity of the welding spot is halved.

The solution ...
is the thousands of times applied energy control developed by ELMATECH! With this solution the two required values Voltage and current are measured directly on the cap surfaces. The cables required for the voltage measurement are naturally attached to the inside of the welding gun and will be virtually transformed on the cap surface by an arithmetic operation, as if they were connected there.

By the energy control (possible only with this technique), the sheets are heated through specific heat in the joining region just to the point, where they approach and contact in fractions of a second, and with forces below 4 kN.

This results in a higher initial resistance for the spot weld, coming to a better energy conversion with minimal spatter results. The joining process starts with the contact of the sheets and is finished depending on the nuggest size which is needed for the overall sheet thickness.

Conclusion ...
less is often more, or: Also in technology violence is a bad counselor.

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