Luxury car is designed with visualisation software

To achieve the high quality of final fit and finish that a luxury car like the new Bentley Continental Flying Spur demands, designers and engineers at Bentley Motors relied heavily on ICEM's software.

To achieve the high quality of final fit and finish that a luxury car like the new Bentley Continental Flying Spur demands, designers and engineers at Bentley Motors relied heavily on ICEM's surface modelling, surface quality analysis and design visualisation software.

When you set out to design a high performance motor car for the luxury end of the market it is essential that you take into account every tiny, fine detail in order to achieve the highest possible quality of fit and finish in the final vehicle.

Even the thickness of the paint on the bodywork must be allowed for.

That is exactly what the designers and engineers at Bentley Motors' headquarters in Crewe did during the design development of the Bentley Continental Flying Spur, which made its international debut at the Geneva Salon in the Spring of 2005 and began its global roll-out in April this year.

Along with its sibling, the Continental GT, the Continental Flying Spur was created at the company's facility in Crewe, in the UK, where a 550-strong team of engineers worked alongside Bentley's renowned designers and craftsmen and women.

Access to parent company Volkswagen's worldwide engineering test facilities was also of prime importance to the development of the car, which benefited from the use of the group's advanced wind-tunnels, proving grounds and prototyping facilities.

It also benefited from the use of advanced computer-aided design (CAD) facilities, including the ICEM Surf surface modelling, surface quality analysis and design visualisation software suite, which was used throughout the design development of the body and interior.

While it was conceived at the same time and is born of the Continental GT coupe, the Continental Flying Spur four-door Grand Tourer is an all-new design, with only a very few items, such as the design of the bonnet and for the interior, the instrument panel and centre console and the front seats, being carried over from the Continental GT.

Just about everything else, both for the body and the interior, is a new design.

The digital design process for the body of the new car therefore started in the usual way with 'point cloud' data from a 3D scan of the styling clay model being imported into ICEM Surf, along with the rendered 2D sketches that had been created during the early concept design and styling phase using Photoshop.

The 2D styling sketches of the interior were also scanned and imported into ICEM Surf for use in the design development of the vehicle's interior components.

This 'dumb' data formed the basis of the modelling process that would then follow to create the 'intelligent' Class A surface data required for the manufacturing processes.

An important capability of ICEM Surf at this early stage in the design development process was the ability it provides to model surfaces dynamically in the context of the engineering CAD model of the vehicle 'structure', without the need to carry the memory overhead of the full engineering solid model.

This enabled a digital assembly model of structural components to be imported from the engineering department's CATIA solid modelling-based CAD/CAM system as a 'light-weight' model and to be displayed in 3D space within the ICEM Surf environment.

This assembly model was then used as a visual reference during the surface modelling process to ensure that no parts of the vehicle body or interior interfered with any of the engineering 'hard points'.

Where any problems arose, the software enabled the surface design team to 'stretch' the surface model over the underlying vehicle structure, without losing any of the original design intent or surface 'character'.

Any issues that were identified at the weekly design review meetings - perhaps a surface that might cause problems during the die stamping process - were dealt with either physically on the clay model and then re-scanned, or directly on the virtual model using ICEM Surf's ability to modify and visualise surfaces in real time, without the need to recreate any geometry.

Although the clay model was the 'master' model in the early stages of the design development process, once certain, specified 'project gateways' had been passed, the digital surface model became the master model.

From that point on, everything was undertaken in the virtual world.

Also at these points, the surfaces team could begin releasing design data to engineering.

This did not mean that the surface model would not continue to change and to be refined.

However, the data were robust enough to allow downstream activities such as tooling design to start.

In practice, surface data was released to manufacturing at different stages, for example when, over the length of the car, it was +/-10mm nominal, then +/-3mm, then +/-1mm and eventually the final production release.

It is during this process of refining the surface model, when filets and flanges are applied, surface-to-surface transitions are examined and reflection lines are analysed, that the way things at Bentley Motors begins to differ from the way most other automotive design and manufacturing companies do things.

It still produces the Class A surfaces in the same way that any other vehicle manufacturer does.

However, unlike mass production automotive companies, these are not the surfaces that Bentley's manufacturing team will work to in the tooling design process.

That's because, for the vehicle body, they represent the top surface of the paint finish, that is, what the customer actually sees; not the top surface of the underlying metal.

"The 'piano finish' paint on the body of a Bentley car is approximately 0.3mm thick", explained Jeff King, Digital Design Data Manager, Styling Department, Bentley Motors.

"This means that on the four-door Continental Flying Spur, there is a difference of 1.8mm between the body-in-white (BIW) and the finished vehicle when you measure from the trailing edge of the A pillar to the leading edge of the C pillar".

"Unlike a mass produced car, for a luxury vehicle like the Continental Flying Spur that difference needs to be allowed for in order to meet the final fit and finish quality targets".

This meant that while the surface engineers were going through the surface analysis and diagnosis process to adjust, refine and measure the gaps between adjoining body panels, they were referencing their work to the top surface of the paint finish.

Once the designs had been approved, they then used the software to generate the data representing the top surface of the metal by applying to the approved surface models an offset measurement equal to the paint thickness.

ICEM Surf then effectively shrunk the surface model by this offset measurement over the entire surface of the body.

The two resulting sets of surface data, representing the BIW and the finished, painted surfaces, were then provided to manufacturing for tooling design to be finalised.

One of the more important project gateways during the development of the Continental Flying Spur is what is termed the digital data control model (or DDKM) event, which is common to all Volkswagen companies.

Here, ICEM Surf's integrated, high-end design visualisation software, Real-Time Renderer, was used to generate high quality visualisations of the exterior and the interior assemblies of the car from a variety of angles.

These photo-realistic design visualisations were then displayed, along with sections and earlier design iterations, on Bentley's in-house 3.5 metre square LCD projection screen for examination and design approval by the company's senior management team.

The end result of these virtual design review sessions was that the process of signing off and releasing surface data to manufacturing in stages was speeded up considerably.

"One of the benefits of using the ICEM Surf Real-Time Renderer in our design reviews is that it doesn't need specialists or dedicated visualisation experts to run it", said Patrick Crutchley, Manager, Class A Surfacing, Bentley Motors.

"We run it on laptops and the engineers do the job themselves, using live design data".

But the use of these high-end design visualisation software tools did not stop at design reviews.

An important event in the build-up to the public launch of the Continental Flying Spur at the 2005 Geneva Salon was the technical press launch.

For this, the ICEM Surf Real-Time Renderer was again used to create high quality, photo-realistic images of the car, incorporating shadows, self-shadows, high-lights, reflections and materials, such as the wood veneer used on the interior.

They also included turn-table animations.

These visualisations were then 'burnt' onto the CDs included in the press packs.

This use of high-end visualisation is something that Bentley Motors is beginning to do more often, as it enables the sales and marketing team to begin to prepare marketing material without having to wait for an actual car to become available for photography - which inevitably, is at the end of the development programme, leaving very little time in which to produce everything.

Summing up the benefits of using ICEM Surf in the design of the Bentley Continental Flying Spur, Bentley's Jeff King said: "It enables us to visualise the finished product to a much higher quality, much earlier in the development programme than is possible with other CAD tools".

"This means that we can wait until everyone is happy with the shapes before we start releasing data to engineering".

"Before, we would have needed to produce physical prototypes in order to get a feel for what the product looked like".

"Now we can do it digitally and release usable data much earlier to tooling development".

"This cuts down the number of prototype parts needed and reduces the overall development time".

"We can also undertake more design iterations within a given time-scale, which leads to higher quality designs, sooner", he added.

"This helps us to achieve the high quality of final fit and finish that is expected of a Bentley car".

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