Product Design Support
Briggs & Stratton new product engineering came up with a unique idea to drive and activate engine valves in order to comply with the latest environmental and noise standards as well as to reduce overall fuel consumption. They named this system DOV for Direct Overhead Valve.
The engineering and purchasing group approached The Diemasters to help with the engineering of the tooling and production process for the stamped components as well as final assembly. With all the R&D and extensive testing required, the project lasted 3+ years. The result was an exceptionally stable and cost-effective process.
One of the stamped components, made from .105” (.2667 cm) thick alloyed steel, had to accommodate, in perpendicular fashion, a 5mm engineered set screw at one end. This called for a precisely formed feature, which in turn needed 3D machining and tapping in secondary operation, as well as assembly of the set screw and jam nut.
Since this system controls the opening and closing of the engine’s valves, the torque and dimensional requirements were very stringent. Various final assembly attachment methods were tested. The chosen method calls for the short lever stamping to provide a 70+ tooth spline, which normally would be machined by a gear tooth manufacturer.
The Diemasters-engineered tooling and process provides a perfect spline and precisely stamped/formed curl. The subassembly system machines the curl feature in 3D, threads and automatically inserts and drives the 5mm screw and 5mm jam nut to proper height and torque.
This subassembled part is then used in the final assembly system, which attaches all of the components in a unique process developed jointly by The Diemasters and Briggs & Stratton. The precise nature of this product calls for constant process monitoring and various poka yoke devices, which were designed and built into the stamping tooling, subassembly and final assembly system.
See a video by Briggs & Stratton about the DOV.