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Automotive Valve Body Assembly

The manufacturer/assembler of an automotive valve body assembly wished to locate the upper and lower valve bodies during sub-assembly. Their intent was also to utilize locating pins during final assembly to locate the transmission case. The total cost of their assembly was being monitored very closely, and they were in search of a product which met all their alignment specifications. Machined Solid Pins and Slotted Spring Pins were trialed, but neither provided the lowest installed total cost and both were difficult to install. The Solid Pin required a very precise hole, it increased the overall assembly weight, had a higher installation force, and was more expensive overall. The Slotted Spring Pin did not provide precise enough critical alignment to the finished transmission case, and it could not be automatically fed due to fact that this type of pin is not very straight, the gap can cause nesting and interlocking, and the imperfect chamfers on the ends of the pins makes it difficult to start the pin during installation. The customer approached SPIROL for help in achieving their overall objective of reducing hole preparation time, reducing the weight of assembly, lowering installation forces, and simplifying the assembly/part feeding process within the plant.

app coiled pin automotive valve body close up top

app coiled pin automotive valve body close up right

The assembly consists of two die cast aluminum valve bodies (upper and lower). The valve bodies needed to be "pinned" in two places 180 degrees from each other. The overall assembly could utilize a interference fit or a clearance fit depending on the overall true position needed in relation to both valve bodies and the mating transmission case.

Considering that the valve bodies are manufactured from aluminum, the light duty Coiled Pin offered the optimum balance of strength and flexibility that exceeded all of the performance requirements for this particular application at the lowest installed cost. The SPIROL® Coiled Spring Pin offered the flexibility for the customer to pick their desired fit with minimal changes. Evaluation of the assembly revealed that a pin could be fixed in the lower valve body, align the upper body and provide a clearance fit in the transmission case for ease of manual assembly. Because Coiled Spring Pins utilize the same nominal hole size configurations (except with a wider overall tolerance) as standard machined Solid Pins and Slotted Spring Pins, this recommendation was validated and implemented as a running change.

Coiled Pins are designed such that their pre-installed diameter is larger than the recommended hole. The diameter is compressed as the Coiled Spring Pin is inserted. Once installed, it retains itself by exerting constant radial force against the hole wall as it attempts to recover back to its pre-installed diameter. This flexibility enables the Coiled Pin to absorb the widest range of manufacturing tolerances of any other press fit pin while simultaneously providing the required retention force. The clean, cut square ends of the Coiled Pin provide a generous lead-in for insertion of the pin as well as for assisting in the alignment of mating components. The combination of the Coiled Pin's straightness, it's square ends, concentric chamfers and gap-free configuration makes it ideal for automatic feeding and assembly. Finally, the lightweight construction of the pin achieved the weight reduction goal, as well as the desire to lower installation forces.

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Coiled Spring Pins

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