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Envisage's P42 Shape concept for a mid-2020s autonomous vehicle.

3D printing helps speed concept-car development

Engineers who have literally sweated the rigors of concept-vehicle development will understand the scope of Bill Walsh’s professional life. As Group Engineering Director at Envisage, a U.K.-based engineering services company, Walsh is involved with every aspect of auto-show concept car creation.

In his world, the clock always seems to tick faster than it does on even the most aggressive production-vehicle programs. Deadlines loom larger and the pressure can be far greater. Panel fit and surface finish, for example, have to exceed the quality standards of an OEM’s production models.

Walsh says this isn't a problem, however. “It is possible to create one-off parts from pretty much any plastic polymer/composite/metallic material or equivalent; 3D printing [additive manufacturing] plays a very significant part," he told Automotive Engineering, with the aim to achieve high fidelity in terms of tolerances and finish.

Concept vehicles are part of Envisage's business of design, testing, validation, manufacturing and engineering of prototypes and low-volume production vehicles. The U.K.-based company also designs and manufactures premium-quality bespoke cars for private individuals. While some of its customers prefer anonymity, Envisage’s client base includes Jaguar Land Rover, Bentley, Rolls-Royce Motor Cars, Tesla, Volvo, the London Taxi Company, Nissan, Williams Advanced Engineering and Mercedes Petronas GP.

Mapping the build process

Concept car programs have various goals. They may be a one-off to gauge public reaction to styling aesthetics or interior design and features. They may be non-runners or have a “make-do” powertrain. They may presage closely a production model or be a technology demonstrator, with hood raised to reveal a new powertrain to the world.

Show-car builds are typically initiated by an OEM, with focused meetings to discuss precisely what is required, what architecture is to be used and to which hardpoints have to be adhered.

“Typically, a build for a premium, fully functional bespoke vehicle takes about 26 weeks,” said Walsh. Build support elements involve mechanical, electrical, technical, and design leads. Major workshop-build "gateways" or milestones in the program schedule include interior, transmission and powertrain ordered by the start of week 7. Glazing delivery is by week 8; exterior panel delivery by week 10. Interior finish is by week 18.

The build is divided into a dozen stages, shown in the accompanying table.

Alongside OEM concept car building, Envisage’s bespoke vehicle creation has grown significantly, bringing 21st-century technology to an art that first became established for horsedrawn carriages. Walsh says that in recent years there has been a resurgence of the art of coachbuilding, with traditional design houses producing low volume, high value exotica-themed rebodies.

But what would once have been a low-tech, artisan business for vehicle creation, now sees Envisage (it now incorporates the specialist consultancy Concept Group International) using modern processes, allowing whole steps in development and build to be removed.

For its bespoke projects, Envisage normally uses existing vehicle platforms, based on required performance/dynamic characteristics/dimensions. "A quick way that we can select a platform is to obtain a catalogue CAD model which is freely available on-line (usually created by games/graphic designers). Once uploaded onto our Creative Design software packages, we can quickly create digital sketch models to see if the donor platform's wheelbase, track, primary crash structure and seating position can be maintained, while honoring the character of the desired design.”

VR tools and cloud data

Use of a virtual reality (VR) headset is likely to be used soon to enable clients to view an early digital sketch model superimposed over an actual donor vehicle. This enables a level of confidence to be gained of the finished design without hard model creation.

Once the design proportion model is approved, the donor car can be agreed. At this stage accurate data of the base vehicle must be captured. Typically, the car will be ‘torn-down’ [dismantled], in stages. At each stage the donor vehicle will be carefully scanned to provide a reference for key mounting and interface points, such as seat mountings, fuel system and cooling system.

“The quality of scan data captures has been and continues to improve at a pace, again helping with the confident creation of the new data which will inform the build of the coachbuilt structure and panels,” stated Walsh. “Until recently, we would only receive ‘cloud point’ data from the scanning activity and this would require manual surface creation."

He noted that essentially, a 3D dot-dot would be a manual process and, as such, error-prone. Recent years have seen the emergence of true automated post-processing of cloud data, using tools such as 3D Systems' Geomagic, which can create an automated surface creation from scans. This ability takes out the human error element previously seen from the manual surfacing process, Walsh said.

Aero surfacing

As a project progresses to the detail engineering phase, improvements in analysis software are facilitating optimization of the design of replacement body structures, such as aero surfacing and cooling performance. This ability can be used as evidence to both customers and homologation bodies to prove the vehicle compliance to certain standards.

"Previously, this could only be achieved through physical, sometimes destructive testing," explained Walsh, noting that process's high cost. But 3D printing enables engineers to design-in undercut (non-moldable) conditions and ignore the risks of surface witnesses of sink marks and weld lines.

"Eventually, when process time and cost are reduced, 3D printing will be the production method of choice for pretty much everything,” he claimed. However, a gap in 3D printing/additive technology still exists in the creation of large and low thickness gauge panels such as aluminum skin panels. But this is an area where traditional skills can also be applied in the auto industry.

The process Envisage currently uses is a mix of both wheeling and hammer-forming, decades-old methods. The results provide a foundation for perfect paint finishing and allowing for the creation of intricate shapes. However, the company "is looking at potential ways to modernize and further improve these processes, with studies into 3D printing of tools and preheating of tailored blanks to further speed up manufacture,” Walsh reported.

He is confident that the mix of old and the new technologies will continue to provide ever more creative possibilities for designers and for robust bespoke solutions for individual vehicles.

“We are able to provide accurate visuals without the need for expensive models and we are able to create, within reason, pretty much anything across the vast realm of materials— including carbon fiber—and finishes now offered by 3D printing,” he said.

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