I Can't Believe It's A Stamping!™

Case Study #1: Cold Formed Roller Finger Follower

Many components that are typically manufactured by alternative methods, such as casting, powdered metal, machining or metal injection molding (MIM), or processes that require costly secondary operations such as grinding, can be designed as a single stamped component. The Engineering and Project Management team at Okay Industries, Inc. provides product and process solutions that can significantly lower the overall cost of a project. Employing OKAY's Production Proven Protoytping process, customers have the confidence that these sophisticated components can be produced as cost effective stampings.

The traditional manufacturing method for Roller Finger Followers (RFFs) in the automotive industry was casting and expensive secondary operations such as boring, grinding and lapping. These RFFs performed satisfactorily; however, the high cost needed to be reduced, especially as engines were being designed with more valves.

To reduce cost, the automotive industry moved to a stamped and formed (folded-up side walls) RFF, but this design had several disadvantages. It was heavier and less stiff than the cast version, which had an adverse impact on fuel economy and emissions. In addition, because of the folded up side walls, the cross section was wider than the cast version. Finally, these stamped components also required the assembly of a clip in the socket area for final assembly into the engine which also increased costs.

Okay partnered with its customer to understand the critical requirements of the application and developed (and joint-patented) methods for manufacturing a lower-cost stamped RFF that was lighter, narrower and stronger. Okay's method is to stamp and forward extrude an RFF with the same configuration as a cast part. The parts are net shape stamped, heat treated and shipped to the customer without adding any additional components or secondary operations.

There were many challenges to developing an RFF as a stamping. One was creating valve stem guide side walls long enough so the parts would not tip over during assembly. OKAY satisfied this requirement by forward extruding material into a die cavity that produced net shaped valve guide side walls that keep the valve stem aligned during assembly.

While this process worked, tooling components would fracture after very few parts due to the forces involved. To get acceptable tool life, OKAY engineered a tooling concept that pre-stressed the tool components by heating retainers and super cooling die components. When assembled together, the retainers and die inserts return to ambient temperature causing the retainers to shrink and the die inserts to expand creating an environment that is very robust, resulting in increased rupture strength for tooling components. These changes resulted in production runs that now exceed 100,000 cycles.

Another challenge on the RFF was maintaining the positional tolerances between closely related features such as, cross-holes, pallet, and socket areas for the Hydraulic Lash Adjuster (HLA). By first qualifying the pallet and socket locations at the same time and then using these features at every feed pitch of the progressive die, the cross holes are pierced in line relative to these features holding a total positional tolerance of .002.

There is also a requirement for a .010" diameter hole in the socket feature of the RFF to spray oil on the roller bearing assembly to reduce friction. Under conventional stamping processes, a hole this small through .098" thick material is not feasible. While OKAY's customer proposed utilizing laser equipment to produce the holes in a secondary operation, OKAY developed and patented a process to produce the oil hole in the progressive die at minimal cost.

An added requirement for the RFF socket and pallet areas was to be free of remnant material chips and surface marks or imperfections caused by the chips. An in-die flushing system was developed to minimize the problem. Also, an on-line vision system is installed at the press to inspect the quality of the surface of both the pallet and socket areas. There are 18 sensors in the die that monitor not only part and slug ejection but also dimensional features within the part to ensure PPM commitments are achieved.

Okay is now in volume production of stamped RFF's with excellent quality and reliability, and is exploring many other RFF applications.

Okay Industries, Inc. is a supplier to the Automotive, Medical/Surgical, Electronics, Defense/Aerospace, and other Specialty Industrial markets requiring high precision and low cost stamped solutions. All tooling and assembly systems are designed and built by OKAY's staff.