Case Study 3D Systems Solid Imaging

Porsche

@Work: Case Study-PorscheMaking the Best Better

The Porche name is synonymous with high performance and excellence, but staying the best means striving to be better. Porsche's engineers are doing just that, and stereolithography helps them by offering new ways to analyze - and solve - old problems.

The heartbeat of an automobile is the "bang!" of the fuel burn in the combustion chamber. Clean burn, strong heartbeat, healthy engine. A "cold" cylinder emits excessive hydrocarbons. A "hot" one "knocks" the life out of the engine. Efficiency means more than health: environmental restrictions for automotive emissions spell "no sale" for inefficient cars.

Getting the True Picture
Porsche's Motorsport Group realized that increasing the effectiveness of the coolant distribution system and maintaining cylinder temperatures at their optimum values would boost engine performance.

However, testing the coolant distribution system, using traditional methods, is time consuming, expensive and occasionally unreliable. Using cast components on a test bench, as with most existing methods is often only possible at the later stages of a project and the test adaptations - runners for sensors and cut-outs for optical systems - may compromise the test data. Finite Element Analysis (FEA) - mathematical approach available early on for three-dimensional flow computation - offers advantages over the "cut and try" techniques but costs dearly in time and money. Since accurate FEA computations require high-quality nets with many cells, more than three months may be required for the finite element meshing of a complete water jacket, including cylinder and crank case. Costs may exceed $50,000.

Using stereolithography (SL), Porsche devised a new approach to this problem. Translating CAD data via CAT-Slice into the SLC format, Porsche built a transparent flow model of a cross-flow water jacket for a high performance V6 racing engine, including all the crucial sections of the crank case and cylinder head. The components were produced on an SLA 250, operated by the European Technology Center at 3D Systems, GmbH, using Cibatool SL 5170 epoxy resin and the ACES buildstyle. Since SL builds the model directly from the CAD data, accurate representation is assured.

Over 60 sensors in the water jacket helped determine local flow temperature and pressure conditions. The exceptional transparency of the model was key to the success of the test. Very tiny air bubbles were injected into the coolant fluid and their motion recorded with a high-speed video camera imaged right through the part. A careful frame-by-frame analysis of these images exposed stagnation zones, revealing insufficiently cooled sections.

Moving Closer to Perfection
This process enabled Porsche to identify unacceptable coolant supply distribution patterns through several of the engine's cylinders. These critical sections were removed, redesigned by CAD as required, and fabricated again in transparent Cibatool SL 5170 epoxy resin. With these modifications, Porsche quickly tested variations on their flow channel designs. About one week per iteration was a typical lead-time - total turnaround time for the entire project was four weeks.

A total project cost of only $23,000 - including data conversion, part orientation, build time, post-processing, and delivery - resulted in significant cost savings over traditional methods. More importantly, using SL meant that "all the necessary testing and design changes were carried out before a single dollar was spent on tooling." Problem solving with SL - the manufacturing savvy that keeps Porsche a winner.

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