The modern turbo diesel engines have increased their performances but also have to face new severe requirements regarding their emissions.

The use of exhaust gas recirculation (EGR ) can help engine manufacturers to keep under control the emissions in order to accomplish to the Euro4 requirements.

In order to improve EGR system, VMMotoriSpA, Cento, FE, Italy, decided to test different alternative intake manifolds.

Thanks to VM engineers’ good knowledge of rapid manufacturing techniques, only few weeks were spent to reach the best performance of the manifold and the engine.

Selective laser sintering

Three different models were used, made by CRP Technology in Windform XT and selective laser sintering, and each prototype was prepared with

a typical lead-time of two-three days, shortening 10 times or more the standard lead-time for this kind of product.

With the first model V1, they realised that it was possible to use the Windform XT intake manifolds for its dyno tests with no problem at all; then they worked on the releases V2 and V3, in order to optimise the partitioning of EGR on each cylinder, reaching the goal of a maximum of fourpercent of difference among the four cylinders (as a target for Euro4 emission level).

The usual standard lead-time for a sand cast aluminium intake manifold is about two months. With rapid manufacturing, it is two or three days.

Thermal and mechanical stress

In the table (see page 88) the thermal and mechanical stress applied to the manifold, during normal engine use (real life engine operating points where the EGR is activated so the intake temperature is increased by mixing fresh air and hot exhaust gases), and the H2O Temperature values (water is the coolant fluid, flowing in a duct beside the manifold, increasing its temperature, because of reduced heat exchange trough the wall), without affecting its functionality at all.

The same manifold also supported some tests lasting 2.5 hours, with the engine at the maximum output, and at the end, it was still perfect, and ready to be used again.

For the line production of this new Turbo Diesel Common Rail2000cc engine (Engine RA420DH6 – 4 Cylinders, 16Valves, 110KW@4000Rpm, Euro4), engine designers decided to use aluminium manifolds and when they tested the first engines, they observed exactly the same results of Windfrom XT manifolds. It demonstrates how reliable and useful can be a study done in a incredible short time, thanks to WindformXT properties. The new Chevrolet Captiva will be powered by this engine.

Headlight washer cover flap

Meanwhile, an immediate delivery of 100 Gallardo’s

pre-production models to the first dealers and customers was required and Lamborghini chose components made with a Rapid Manufacturing technology.

The Rapid Prototyping materials available on the market until that moment did not reach the minimum mechanical and thermal properties that those application was requiring: once painted the part had to be fitted directly on the car. The suggestion was selective laser sintering and Windform materials.

It was a very exciting challenge as the Gallardo can easily reach 300km/h and has to resist at every climatic condition, both in winter (-20°C) and in summer (50–60°C).

Show defects

The components previously made from injection moulding were not suitable for this first phase. The particular, still at a non-definitive stage, presented some showy defects, due to project and process:

n In closed position: a discontinuity with the rest of the bodywork (hood, bumper and lateral body), the external surface had a different shape in respect to the hood and front headlight's design.

n In open position: imperfections of the inner structure, due to shrinkage of the injection moulding causing defects also on the upper external part.

The first goal was to guarantee the reliability of the component through an increase of some particular points’ thickness.

Some ribs were added close to the hinge of the cover flap and the shape of the external surface was corrected in cooperation with their designers, in order to gain a perfect continuity in the area between the headlight, the hood and the headlight washer cover flap.

Once the co-engineering was finished, a first prototype was realised in a couple of days in order to check the fatigue resistance, through several different working cycles.

Dimensional inspection

A specific dimensional inspection, made through large reference points on each piece, standard operation in Formula one, would have excessively increase

each component cost, this one being a mass production part.

That is why this inspection was made for the very initial components and for the mask used to check the other parts.

The last problem was that the original particular had a shiny black colour, similar to the headlight’s one. The painting came up perfectly, just considering the correct temperature for Windform material.

Even the scratching test, performed to test pigmentation’s wear resistance in face of asperities at high speed, did not highlight any problem.

The remaining parts were finished and the first 100 cars were delivered with Windform-sintered components fitted.

In a couple of weeks the cover flaps were sintered, superficially finished in order to have the minimum roughness for an excellent surfaced finish, painted and assembled on the conveyer.

Enter 88 or 'tick' at www.engineerlive.com/ede

Dr Eng Livia Cevolini is with CRP Technology, Modena Italy. www.crptechnology.com