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Starting situation
There are often assembly-related corrections when preparing a new forming tool for series production, because the shape of the produced sheet metal must be compatible with all other installed sheet metal and add-on parts. Flange surfaces and trims are often affected by these corrections. In this case, the cut-out for the roof window must be enlarged by 0.5 mm on two sides for a new tool for the production of a sheet metal that forms the outer panel of a truck roof assembly. The trim in question is a segmented cut, where the trimming operation is carried out in several forming operations segment by segment due to the large overall length of the trim. Two tools in the tool set were affected by this change. The affected cutting length is approx. 1,400 mm in seven trimming segments. It is necessary to correct all affected segments with high accuracy in order to achieve a clean cut of the sheet metal over several operations. During a trimming correction, the die blades in the lower part of the tool, the punch blades in the upper part and the blank holder, which fixes the sheet during trimming, must be machined.
Procedure
Once all the segments to be changed had been digitized, the data set of both tools was transferred to the same alignment. In this way, the modification design can be carried out identically in all segments so that the segment trim continues to form a uniform trim over the entire length after processing. In this case, material was removed from the punch blades with our CNC milling system in order to offset the trim. Material had to be applied to modify the die blades. This was carried out in collaboration with our partner Lasertechnik Kreiensen. By combining the ALFLAK mobile laser welding system with our measuring technology, it was possible to achieve a sufficient material application of a few tenths of a millimeter above the final dimension of the modification. The applied material was then milled to the final contour of the modification using our CNC milling machine. Thanks to the low material application, we were able to achieve a very short throughput time. It was not necessary to repair imperfections in the applied material, as the laser welding process is very reliable for hard coatings (> 60HRC). At the same time as machining, our tool mechanic was able to adjust the contour of the blank holder manually; the high precision of CNC machining is not necessary for its function. Finally, all modified areas of the tool were digitized in order to incorporate the changes in the existing CAD model of the tool.
Advantages
The efficient interplay of measuring technology, laser welding, CNC machining and manual processing has drastically reduced the costs and throughput time of an otherwise very time-consuming trimming process. The forming tools for truck components, which are otherwise very costly to transport due to their size, have not left their place of use. As a result, the very costly special transports were eliminated, and the CO2 footprint of the entire change was reduced to almost zero.
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