Lotus Cars, based in Norwich, United Kingdom, is known worldwide for creating award-winning sports cars at the forefront of vehicle design technology. The company has also developed a reputation for exceptional quality.
The Lotus Engineering Company was originally founded by Colin Chapman in 1948. Under his direction, the company recorded 79 Grand Prix wins and seven Formula 1 Constructors' World Championships. The emphasis of the business is somewhat different these days, but Lotus still upholds the competitive spirit through Lotus Motorsport, a one-make race series for the Sport Elise, and provides technical support for external customers competing at all levels of national and international motor sport. The latest new model in the Lotus range, the Exige, is quite literally a racing car that has been converted for road use. The new model uses the same aerodynamic body shell as the Sport Elise, although some changes have been made to make the car road-friendly. As with the Elise, demand for the new model is high, so anything is welcome that can enable faster production.
The company realized it needed a system that could check the positions of components as the cars were assembled, since all Lotus cars are built by hand. The largest in production is the Elise model at around 3,000 cars each year, and each of these takes around 200 hours to assemble. However, a problem arose that was related to the fixtures used to ensure the correct alignment of components as the cars were assembled. Any movement of or damage to the fixtures would result in parts being attached in the wrong alignment. The incorrect positioning of an early component such as the steering rack causes serious problems further down the line. Worse still, if an incorrectly fitted part is only found at the final testing stage of the car, a lot of work is needed to access the part and correct the problem. In the past, this would only become apparent when subsequent parts would not fit into their specified positions. To combat this problem, the fixtures were regularly removed for checking on a CMM. Since production could not continue during this checking, the measurements could only be made during weekends.
The initial application of a Faro arm from Faro Technologies (Lake Mary, Florida) allowed inspection of parts against the CAD model as they were assembled. Another advantage the arm offered was that it could measure a complete car side. The CMM the company previously used was not large enough to inspect the car as it neared completion.
The company also found that the speed of inspection made possible with Delcam's (Birmingham, England) PowerINSPECT inspection software, combined with the Faro arm, made a significant contribution to production efficiency. With the Faro arm and PowerINSPECT, inspection can be undertaken on the line, with minimal disruption to production. As a result, inspection can be carried out more frequently, allowing any problems to be identified earlier and corrected more quickly.
"With PowerINSPECT, we have the ability to check a complete body side of a car within 10 minutes. This includes the time taken to set up the Faro arm alongside the production line, to set the datum and to check selected points and sections on each of the individual panels that make up the complete body side," says Chris Balls, engineering workshop supervisor at Lotus.
The portability of the Faro arm/PowerINSPECT combination is another advantage. "We can inspect jigs and fixtures directly with the CAD model at the production point and make any adjustment there and then," says Mr. Balls. "We also do a final verification once they are set up."
Similarly, portability is important in the manufacture of sub-assemblies for the cars. "We also use PowerINSPECT to verify the build of sub-assemblies at the point of production. For example, with a door, this would include the positions of brackets, hinge points, glass channels, door handles and so on. This is achieved by loading the different CAD files into PowerINSPECT as the door is assembled. Again, any problems are highlighted instantly, allowing solutions to be implemented much faster," Mr. Balls says.
Overall, the Delcam software has meant increased productivity, while maintaining Lotus' high standards of precision.