Plastics Engineering - 4/1/99 issue

COMPLEX DESIGNS
Heavy Gage thermoforming's Traditional image as basically a limited process for fabricating flat sheets with a minimum of complexity of design and shape is becoming outmoded, as interactions among materials, machinery, and CAD/CAM technology continue to progress. Richard Freeman, President of Freetech Plastics, Inc., sees the process, which typically involved simple, perpendicularly assembled flat shapes moving toward more complex curved freeform ergonomic mating surfaces. This evolution has been made possible by the ability, produce more intricate precision molds through 3D solid modeling and computerized machining techniques. With thermoforming now catching up in the use of these technologies, Freeman expects it will become increasingly competitive with processes such as injection and blow molding. While thermoforming has always offered economic advantages for short production runs, the expansion of its capabilities through the computerized machining and mold making techniques now makes it more Possible to match the form and complexity that have always given the alternate processes a competitive design edge. Freeman adds that often an optimum design could involve a combination of materials, such as sheet metal and plastic, and different fabrication processes, such as stamping, reaction injection molding (@, and pressure thermoforming. He suggests that the resulting necessity of painting the contiguous surfaces, rather than using sometimes preferred molded in color, can become a "plus." In Freeman's view, the designer is offered a significant degree of flexibility to retain color matches while combining different materials, surfaces, and textures for optimum functionality and stylistic effect. As an example, Freetech Plastics manufactured the housing for a piece of robotic surgery equipment produced by The Intuitive Surgical Company. The product combines space age robotics and electronic and video technologies to do heart surgery through a one-inch-diameter hole, eliminating the need to open the Patient's chest. The equipment simultaneously reproduces hand movements at the surgeon's console with electronically d micro-movements in the operative field. Given that there were no flat or perpendicular planes from which to reference dimensions, each of the seven thermoformed covers that enclose the surgeon's console had unique and difficult requirements in relation to the need to precisely match the contiguous contoured surfaces. As a result, extensive 3D machining was required to exactly replicate the multiple surfaces from the electronic files. Also, numerous breakaways (mold core releases for undercuts, negative draft, and recesses) were required to properly accommodate the equipment's internal components. Sophisticated 3D machining capabilities also were necessary to produce fixturing to hold the free-form covers in their proper x, y, and z planes for precise positioning of mounting blocks and ball studs on the parts, and to provide for accurate post-mold trimming. It was critical that the location points be precisely established to ensure correct mating of the freeform covers, together with the complex components attached to them, to a steel frame and weldments within the equipment housing. Royalite R-59 fire-retardant ABS, was chosen for the base material for the covers, It satisfied the requirements of high draw ratios and undercuts, and high detail replication of smaller features. The thermoformed covers were then coated with urethane paint and included company-identifying silk-screened graphics.

Freeman says that experienced programmer-toolmakers can now duplicate almost any kind of complex surface that can be generated by even the most sophisticated software, and then convert the information to CNC machine code. Large formed parts with sharp, molded-in details can yield highly stylized, futuristic-looking products. For the surgical console Lunar Design an industrial design and product development firm was responsible for the modern look and feel of the product. The bottom line is that with the advances in the Thermoforming process Freetech was able to bring the forward-looking concept to fruition.

Freetech Plastics, 3120 Osgood Court, Fremont, CA 94539. Tel: 510-651-9996; Fax: 510-651-9917.