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CMMs in the Styling Studio: More Capable than Before

Rover is using CMMs in the styling studio, not only for purposes of measurement, but also for model milling. Capable CMMs are helping bridge the gap between styling and engineering. By Rolf Röhm, Product Manager Horizontal-Arm Systems, Carl Zeiss Corporation and David Hope, Sales Manager Measurement & Testing Division, HK Technologies Ltd.

Revolutionary leaps in CAD-enabled modeling and holography have dramatically altered the transition of a car concept from the design stage to the engineering phase. Even so, the traditional clay model remains a mandatory stop between the designer's vision and engineering's cycle-reducing CAD tools. For styling and design purposes, nothing works better than an actual model. Meanwhile, within engineering, digital manipulation is raising the bar continuously. CAD-triggered opportunities to enhance product development speed and efficiency seem unlimited.

To capture this potential, clay models must feed the insatiable appetites of CAD systems. How do we influence three-ton clay models and nimble cyberspace configuration to converge rather than collide?

One approach, particularly in European styling studios, is a new generation of horizontal-arm coordinate measuring machine (CMM). To satisfy CAD requirements and capture cycle time improvements, automakers including FordRenaultPorsche and Daimler have extended and redeployed the data acquisition capabilities of CMMs built for their styling studios.

During the last 24 to 36 months, for example, designs for new, state-of-the-art styling studios around Europe have included installation of specialized Zeiss CMMs—as many as 16 in one facility—that handle more than the traditional measurement-and-inspection load. To merge engineering with the design as early in the development process as possible, this new breed of styling studio CMM includes hybrid horizontal-arm systems that function as build tools and  high-speed digitizing devices.

The new CMM philosophy is just one indication that automotive styling and design are more critical than ever. In addition to incorporating a range of new hardware and software technologies, European styling studios are architecturally engineered to remove obstacles to the creative process. Wide-open spaces, for example, are so highly prized in contemporary studios that some manufacturers specify horizontal-arm CMMs suspended from the ceiling.

The new studio within the Rover Group Design & Engineering Centre (GDEC) in the United Kingdom exemplifies the evolution of CMMs utilized specifically for design. The new-generation instruments reflect wide-ranging space, equipment and process strategies aimed at promoting creativity and accelerating product development throughput.

Opened during March 1997 in Gaydon, Warwickshire, just outside of Coventry, the GDEC styling studio replaced an older, smaller space that had been fashioned from a portion of the former Triumph factory in Canley. The GDEC complex, adjacent to the Rover proving grounds, supports the 200 through 800 series passenger cars and Land Rover manufactured at three surrounding plants. The styling studio, home to 27 of 45 new and relocated horizontal-arm CMMs installed at the GDEC, is a key design and engineering workhorse for Rover.

Not Your Father's CMM

At Rover—as well as at the facilities of other European automakers—there are new and higher expectation as regards the results that a styling studio should generate. Not to mention how efficiently and rapidly these results must be delivered. An issue is combining design and engineering operations. Across the board, the CMM emerged as a tool for combining the two disciplines early and easily.

Leveraging the CMM to help manufacturers put automotive design and engineering under one roof—literally—accelerated the transition from inspection device to functional tool. As a result, at least in comparison to the traditional definition, a CMM tailored for today's styling studio is not merely a measuring system. It's a principal design machine. It's also a fundamental tool for accelerating time-to-market.

Finally, although this new series CMM is robust in data acquisition and build tool roles, it must be unobtrusive in form and operation. The equipment must not have unsightly cables, for example, and it must make as little noise as possible.

CAD is Pushing the CMM Envelope

Approximately 500 tons of cast steel horizontal-arm surface tables installed throughout the Rover GDEC would extend more than 1,000 ft if laid end-to-end. More than half of this CMM capacity is at work in the vast styling studio. Dual-column Zeiss SMM-D Series systems modified to provide an integrated solution digitize and mill using the same hardware and the same software. SMM systems in the Rover styling studio handle both a laser scanning probe head for rapid, high-density digitizing, and a rotating milling head for CNC-driven clay model profiling and copy milling.

Why the increased interest in adding accountability and capability to the studio measuring instrument? The answer, of course, resides in leading-edge CAD technology that is accomplishing in hours what previously required weeks. Back when a CMM required three to four days to digitize a clay model profile, there was not much payoff in reducing data collection by a day or two.

Today, in contrast, it's CAD technology that is driving the data density and quality standards. And CMM manufacturers are being asked to respond with laser-enabled scanning that has steadily decreased total digitizing time from the 100-hour mark to less than 10 hours.

Classic Evolution: Doing More With Less

Using a Zeiss DSE articulating sensor holder, hybrid styling CMMs at Rover give designers and engineers five-axis capability for milling as well as digitizing. Although some European manufacturers previously employed five-axis milling centers in design roles, those systems were production-class in design, purpose, size and noise level. Compared to the new milling-capable CMMs in demand among European studios, those five-axis tools intended for metal cutting exceed restrictions on size and sound.

While the cross arm on a production milling system might be 300 mm square, the arm on a new milling-capable CMM designed for the studio is just 100 mm square. In addition, CMM-mounted milling heads are high-speed, low-torque designs that generate little noise.

At the same time, CMMs built for the styling studio must avoid bulk without compromising throughput, repeatability and accuracy. In the case of the systems at Rover, higher machine rigidity and improved acceleration enable the dual-purpose horizontal-arm systems to use large tooling—like milling heads—and maintain performance levels.

Sensitivity to aesthetics and preserving the open space extends to horizontal-arm design features like hiding cables that typically trail or hang from the machines. CMM tables, likewise, are flush with the floor. With guiderails integrated into the table, nothing extends above floor level. As a result, clay models can be moved onto the CMM surface plate easily. And designers can view models from any angle without tripping over guiderails or falling into grooves.

The new systems also solve the long standing problem of clay falling onto the guiderails and obstructing smooth, accurate arm movement. In the new Zeiss design, the guiderails are not located directly below the cover plates, but are instead off center.

In addition, for the first time in a Rover styling studio, CMMs include a lift table that enables the designer to raise a model approximately 39 in. Sculpting a sill or a bumper no longer requires laying on the floor, which enables designers to work more comfortably, more efficiently and with better sight lines. The smoothly raised and lowered table involves no hydraulics or pneumatics. Instead, a scissor mechanism is electronically powered by a horizontal ball screw drive. In addition to being virtually noiseless and mechanically rigid, the lift is significantly more compact. Unlike a hydraulic-type design, the scissor device does not require a deep, in-ground recess to store the vertical height of the lift mechanism.

Design-stage efficiency also gets a boost from the move to even longer measuring plates—up to 100 feet in some installations—that enable engineers to work on three or four models on the same plate. They simply move the CMM when and where it's needed.