The Buhler Die Casting division and Schaufler Tooling have demonstrated their competence by introducing a new concept for manufacturing engine blocks by the die casting process.
|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, evermore 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.|
New, patented die casting tool concept for making Vengines.
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.
Stateoftheart die casting machines equipped with cuttingedge realtime 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 (the Die Casting division of the Buhler Group) teamed up with their colleagues at the German diemaker 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
- timeconsuming 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 costoptimized engine block concepts were developed for making inline and Vengines. 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.
Diemaking and mechanical engineering blended
The difference between an inline engine and a Vengine 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 Vshape at a certain angle in the Vengine.
The revolutionary thing about the two new Buhler concepts is that they are the first to blend cuttingedge diemaking with stateoftheart 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 fulfills 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 fulfills certain functions of the conventional die. This eliminates the need for ejector boxes and ejector tables in the new dies. This and additional weightreducing optimizations enable the die costs for making Vengines to be slashed by 25 percent, and inline engines by 10 percent.
Last, not least, the new concepts also boost productivity. An optimized temperaturecontrol 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.
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 will be implemented in the course of this year. At present, the prototype of a V6engine crankcase is being tested. At the same time, a prototype die is being made for an inline engine crankcase and will be tested this spring in the Die Casting Center Laichingen (DCL).
Buhler is a global leader in the supply of process engineering solutions, especially production technologies for making foods and engineering materials. Buhler is present in over 140 countries and employs some 6,600 people. In fiscal 2006, the Group generated sales of CHF 1,613 million.
For more information, please contact:
Marc Fuchs, Head of Product Management, Buhler Die Casting at Buhler Uzwil
T +41 71 955 21 04, F +41 71 955 21 49
Further information for editors: Corina Atzli, Head Corporate Communications, Bühler AG, CH- 9240 Uzwil, T +41 71 955 33 99, F +41 71 955 38 51, E-mail corina.atzli(at)buhlergroup.com