The production of dies and moulds from high-tensile steel is one of the most demanding machining tasks. Cutting tools are subjected to maximum loads during the roughing process. As a result, the industry is constantly seeking to develop innovations that increase productivity. The latest example in this sector is the Nanomold Gold indexable insert coating developed by LMT Kieninger.
The performance of the precision tools used has a fundamental influence on the success of die and mould making. Steels with a hardness up to 50 HRC have to be machined with great precision and a high level of efficiency. During machining the cutters are not only subjected to extremely high temperatures, but the different cutting speeds on the indexable insert also differ very significantly – from zero at the centre to maximum speed at the largest diameter.
Specially developed for die and mould making
“These strains naturally occur with all indexable inserts, but in die and mould making they are particularly challenging because of the hardness of the material,” explains Christian Krieg, R&D expert at LMT Kieninger, the die and mould making specialists within the LMT Group. “That’s why we wanted to develop a new tool coating that was specially tailored to die and mould making and produce a substantial performance increase.” The specialists have succeeded in doing precisely that with the Nanomold Gold coating for indexable inserts. The coating strategy does not only make it possible to vary the combination of individual layers, but also to select different layer thicknesses. It is therefore possible to combine a top layer that is ideally suited for high cutting speeds with a core coating that also maintains its characteristics at low peripheral speeds.
Tool life improvements of at least 30%
In order to guarantee the durability of the coating, the first layer is always an adhesion layer that forms a soft transition between the substrate and the coating system. This enables Nanomold Gold to offer a high level of chemical and thermal stability and very good protection against abrasive wear. In practical use, average wear-land width is almost halved by the new coating. In steels up to 50 HRC Nanomold Gold achieves tool life improvements of at least 30%.
Successful use under practical conditions
Has this concept proved its worth in practice? A south German car company has tested Nanomold Gold in the production of an upper die for a vehicle door. The material used is a cold work steel 1.2333, tempered to 255 HB. Machining was carried out with a WPR 16 N ball nose copy insert with Nanomold Gold coating. The finishing process for the die takes over 16 hours – a true test of endurance for the tool. However, the crucial difference between the old and new tool became clear after only 30 minutes of cutting: there was a significant reduction in the width of the wear marks on the indexable insert compared to the previous tool. The flank wear at the centre of the blade has improved by 23%. On the circumference of the insert the improvement was 45%.
Process reliability is decisive
“Under these conditions it is possible to increase tool life for machining in die and mould making by roughly one third,” confirms Hanjo Gissler, product manager for die and mould making. In the end, however, this enormous performance increase was not the main factor in the user’s decision to change over to the new tool. The subject of process reliability appeared even more important, which is no surprise really in light of the long total machining time. The very even and much slower wear characteristics along the cutting edge guarantee uniform cutting quality over a long period. “Additionally, the performance data of the tool indicate further potential for optimizing cutting results and the machining process. It’s a combination of two things: higher quality and greater efficiency in production. These prospects enabled us to convince the customers of the great potential that Nanomold Gold offers,” sums up Hanjo Gissler.