in DCL (Druckguss Center Laichingen)
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Representatives of many international carmakers and automotive suppliers examined on 14./15. February in "Druckguss Center Laichingen" a new die casting concept for engine blocks developed in cooperation between Bühler Druckguss AG and Schaufler-Tooling GmbH & Co. KG. The new concept promises reduced cycle times, easier and more favourable moulds as well as higher durability on cooling water jackets.
“Higher productivity, lower costs per engine block and less CO2 output”, says Siegfried Heinrich, managing director from Schaufler-Tooling, describing the most important advantages of the new die casting concept which was presented during the two days at the Laichingen company.
The new process developed by Bühler Druckguss AG and Daimler AG in Druckguss Center Laichingen could turn the future series production of engine blocks to be more cost-efficient, says Heinrich. Anyway it stays in the fore of technical development in engine manufacturing.
At the end of the seventies of the past century, engine blocks were for the first time no longer made from gray cast iron, but aluminum. This change in the raw material was triggered by the weight reductions allowed by the appreciably lower density of aluminum – despite the higher material cost. Ever since, light metals such as aluminum and increasingly also magnesium are playing an ever more important role in engine construction. Not least, ever more stringent environmental protection laws also favor the use of light metals. 2006 was the first year that more passenger cars left European assembly lines with engine blocks of aluminum rather than gray cast iron.
Advantages of aluminum die casting
The engine block is made up of two distinct functional units – the cylinder block (upper part housing the cylinders) and the crankcase (lower part housing the crankshaft).
The die casting process has been found to be a very viable option for manufacturing aluminum engine blocks. It is distinguished by high output and flexibility in component design. The attractiveness of the die casting process is likely to increase further still, for the potential of aluminum as an engineering material has by no means been exhausted yet, at least in the field of Otto engines.
State-of-the-art die casting machines equipped with cutting edge real-time control systems such as those manufactured by Buhler allow highly variable selection and adjustment of the die cavity filling process. In addition, with the support of vacuum, they even permit heat treatment for increasing the strength of the components made.
In quest of additional improvements
Aware of the attractiveness of die casting, the specialists at Bühler Druckguss AG (the Die Casting division of the Buhler Group) teamed up with their colleagues at the German die maker Schaufler Tooling to find additional improvements. The goal that the project team set itself was to eliminate the still perceptible drawbacks of conventional manufacture. Ultimately, this would further increase the profitability of the die casting process for making engine blocks.
In an initial analysis, the following cost drivers were identified and dealt with:
- Long cycle times
- Large and heavy dies
- High wear on the cooling water jacket inserts
- Long downtimes due to
- Time-consuming die maintenance (for example tedious removal of the moving die half for changing the water jacket)
- Frequent injection of molten metal behind core slide guides
- Frequent die leakage
- Frequent rupturing of ejector pins
- Uncontrolled die heating and cooling
Based on this analysis and Buhler’s and Schaufler Tooling’s experience, two new cost optimized engine block concepts were developed for making inline and V-engines. This effort was supported by the vast experience that Buhler has accumulated in the supply of over 30 die casting cells for making engine blocks, and that of Schaufler Tooling, which to date has supplied a number of engine block dies. Both concepts have now been patented.
Die making and mechanical engineering blended
The difference between an inline engine and a V-engine lies in the configuration of the cylinders. As the name suggests, the cylinders of an inline engine are arranged in a straight row, whereas two cylinder rows are arranged in a V-shape at a certain angle in the V-engine.
The revolutionary thing about the two new Buhler concepts is that they are the first to blend cutting edge die making with state-of-the-art mechanical engineering technology. This combination of the two disciplines produces a commercially promising solution for manufacturing engine blocks. Thus, for instance, the water jacket and the contour core slide can be pulled by a certain stroke length already after partial solidification of the metal. This reduces the heat input from the aluminum into the water jacket, which in turn appreciably increases the life cycle of the water jacket.
In addition, the project team implemented a number of die design measures. These increase the uptime of the die and therefore the capacity utilization rate of the die casting cell. For example, the contour core slides can be changed on the machine itself with great ease and within a very short time. A special locking design reduces the deflection of the outer slides by as much as 50 percent. This, in turn, reduces the injection of molten aluminum behind the slides while improving the dimensional accuracy of the engine blocks. A new technique for sealing the cooling bores diminishes their proneness to leakage. Furthermore, a concept which eliminates the need for ejectors in making inline engines additionally prevents downtimes.
Machine fulfils die functions
One major problem in conventional engine block production is the very massive, large, and therefore expensive dies that must be used. In the new Buhler concept, the die casting machine fulfils certain functions of the conventional die. This eliminates the need for ejector boxes and ejector tables in the new dies. This and additional weight reducing optimizations enable the die costs for making V-engines to be slashed by 25 percent, and inline engines by 10 percent.
Last, not least, the new concepts also boost productivity. An optimized temperature control design, the freshly developed “Flextool” die spray system from the Acheson company, and synchronized machine motions allowing simultaneous spraying of both die halves save valuable seconds. These features cut the cycle time by 10 to 20 percent, depending on the weight of the raw part.
The height of the casting moulds overall is reduced from 2,15 meter to 1,4 meter and the weight of the moulds decreases from 70 tonnes and more to 40 to 45 tonnes. No wonder there came also carmaker representatives from USA and Japan to Laichingen.
For two years a project team of eight persons from the two companies Schaufler and Bühler is engaged in the presented casting concept. Again and again also experts from Daimler AG joined the team.
Together with Schaufler Tooling, Buhler presented this novel concept to a number of renowned engine block producers as far back as in early 2006. This has triggered projects that has been partially implemented in the course of this year.
Catalogue of Suppliers: Bühler Druckguss AG
Catalogue of Suppliers: SCHAUFLER Tooling GmbH & Co. KG