Durden

Bill Durden, Vice President of Durden Enterprises, Inc., in Atlanta, Georgia, used stereolithography (SL) to develop tooling for the production of a complex, plastic water mixing and dispensing valve. Working on an incredibly tight deadline, during year-end holidays, Durden turned to SL for assistance.

The valve consisted of four unique parts. Durden decided to create three of the molds using traditional methods, while the fourth, the valve outer body, would be built using SL. All parts required tolerances of +/- 0.005 inch to ensure that the o-rings created a water tight seal.

From a pen and ink drawing, a CAD model was generated in Pro/ENGINEER and built on the SLAŽ 250 system.
Once approved by the customer, Durden designed two negative mold inserts, incorporating compensation for pre-determined shrink factors. SL masters of each insert were completed in a build time of less than 32 hours, and required only four hours of finishing.

The SL insert masters were then sent to the 3D Keltool process facility located in St. Paul, Minnesota. The 3D keltool process replicates a pattern, such as the SL master, in very hard sintered metal (Rockwell hardness, Rc between 35 and 55). The result is a set of tool inserts which faithfully copy the original, and will last through large production runs. The final molds made from the SL masters are full production quality and are expected to last for at least one million shots.

The production of the valve, which was delivered on time and under
budget, is only half the story.
At Durden Enterprises, the goal is to "leverage the effectiveness of each tool maker." SL helps them do that. While a simple tool requires only an hour of a toolmaker's time on a lathe, an SL tool takes eight to ten hours to accomplish the same task. However, add the myriad of twists and turns, or lips and grooves in a complex geometry and correspondingly, what would take a toolmaker weeks or months to carve, still takes the SL tool only eight to ten hours.

At Durden, SL allowed engineers to maximize their technology resources and build complete production tools. SL enables the rapid tool making process to proceed smoothly and efficiently.