Article by Shawn Sims, Automotive Editor, NOTCOT
Once a clay prototype is underway, it’s time to take the next digitizing design step. In my last few posts, I have written about the automotive design-and-engineering process I observed at the new Lincoln Design Studio, including my experiences with clay modeling and hand carving the curves on the prototype of the Lincoln 2013 MKZ.
However, sometimes Lincoln craftsmen need a faster and more powerful way to make the designs come to life beyond hand modeling. Inside the Lincoln Design Studio is a massive five-axis CNC (Computer Numeral Control) milling machine that turns digital files into full-scale sculptures. The designers and engineers still work on the car model in clay, but instead of carving it by hand, they use a very large and fast drill, programmed with a digital 3-D model.
Hand carving gives designers a tangible sense of the vehicle and requires a great eye and experience with the material. However, the CNC machine goes where it is told, with the precision of a computer. It is a great indicator of what the digital design will look like once the vehicle goes into production. The fabrication process begins after the designers finalize a car’s digital model. They pass the digital model to an engineer who programs the movements of the milling machine. The CNC machine is a sophisticated device that offers improved automation, efficiency, and accuracy. The engineer can make the CNC machine perform infinitesimal adjustments — the drill can go deeper, spin faster, speed up, or slow down — to ensure the highest quality and most accurate representation of the automotive design. Once the files and settings are ready to go, with a push of a button, this massive machine starts moving, twisting and spinning. In this case, the tiny bit on the end of the drill moved to the corner of the taillamp section and began carving gently into the clay. The machine works around, further smoothing and honing the bumper, taillamp area, and back quarter panel worked with each pass. Even the exceptionally detailed area around the exhaust was milled by the machine. It was incredible to watch this thing at work and to see how detailed it got. The CNC machine has a variety of tools, much as the human sculptor does. Each tool has a specific job, for particular features and cuts. Some tools remove material more efficiently, while others smooth out the car at the very end. Tools are changed frequently, after the machine finishes one pass on the car. With each pass of the CNC machine, the car takes on more details of the digital design. Check out how fine the shavings are. This milling machine, equipped with the right tools, can take off fractions of an inch, giving the auto designers unparalleled accuracy for visualizing details. I was fascinated by the entire process of automotive design, especially the milling machine and hand modeling with clay. The photo above shows “my” completed car (though of course the work was actually done by a professional; I just got to play). The front half is where I spent a good amount of time shaping the fender by hand, while the back is where the CNC mill quickly replicated a digital model. Together, the design and prototyping process revealed a fascinating journey of discovery and invention.