Case studies of precision cutoff and stamping

When the stamping gasket is not good enough

Once upon a time, more than 20 years ago, a major auto manufacturing company came up with a great idea for their fuel injection system: they invented flaps that opened and closed like heart valves, alternating metering and sealing to keep fuel in place. To use the new flap valve, the company needed a seal with thickness, flatness and parallelism dimensions controlled within micron tolerances.

Specifically, the automaker wanted a small, flat ring that would form a surface that fits precisely to the flap surface and is tightly sealed so that no fuel escapes when the flap is in the closed position. The surface of the gasket needs to be prevented from becoming dirty to maintain a tight seal and prevent fuel leakage into the injection system. It also needs to withstand billions of cycles, opening and closing the flaps repeatedly.

The automotive company is looking for a very thin, gasket-like metal ring that is less than 0.050" thick and has micron level flatness, squareness and parallelism tolerances to prevent any surface deformation. The gasket also needs to function perfectly no matter what temperature it is subjected to -- from icy to blistering engine heat. In addition, the company needs millions of these gaskets and wants them at low cost!

Precision stamping options

Achieving a completely flat spacer ring proved to be a real challenge, and automakers struggled to find parts they were confident would not deform under engine conditions.

First, the automaker went to precision Stamping to produce gaskets. At first, stamping the ring out of a sheet seemed like the perfect way to produce flat parts with horizontal particles. In tests, however, the parts did not maintain their flatness and always bent along the body; In addition, the stamping edge of the part will deform.

Next, the automaker tried a supplier that would make spacer rings through fine blanking, a precision metal forming process that is a blend of stamping and cold extrusion methods. Fine blanking uses triple motion hydraulic presses and specially designed dies to produce parts with fully sheared, straight cut edges.

For automotive manufacturers' gasket applications, the fine stamping method produces cleaner shear perimeters than traditional precision stamping. However, in addition to having a higher cost than traditional precision stamping, fine stamping does not produce a flatness that can be maintained over the long term. Automakers are also finding that the particle orientation of these processes is causing them life-testing problems.

The third option is charm

Finally, the automaker came to the field of metal cutting to explore other options to achieve the correct deformation free flatness, sharp edges and outer diameters of its spacer rings. We took a different approach from previous suppliers and suggested using tubing - extruding or using a solid rod or larger tube pulled through a die to achieve the correct ID - to produce a ring which was then precisely cut to the appropriate thickness required for the gasket.

Unlike stamping and fine blanking, precision cutoff produces grain structure in the stretching direction of the pipe, reducing the chance of warping over time compared to flat grains. Stamping and fine blanking can cause pulls and burrs when the material is cut, while precise cutoff can produce sharp corner radii. Precision cutting provides a burr-free cut for very thin materials without end deformation or deformation, and maintains strict tolerances while providing the dimensions required by car manufacturers for their very thin gaskets.

In the end, precision cutoff proved to be the app's always Happy choice. While the process isn't as cheap up front as stamping or finishing stamping, compared to the cost of replacement, the cost is worth it - not once, but millions of times - if an automaker's revolutionary flaps are fitted with doomed gaskets.

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