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Finishing 3

The Evolution of Finishing Machines (Continued)

Product Testing

To date, Delco has produced many millions of the new R-4 reeds and has yet to have a failure in the field. Nevertheless, the reeds are continually subjected to rigorous testing.

In addition to the conventional life test of the entire compressor, Delco also tests the reeds themselves. The test equipment, which can flex the reeds at 12,000 cycles/mm under loads several times greater than that encountered at full compressor load, can also break any reed Delco can make. By testing reeds to failure (the cracked reed shown in the photo was tested to failure at a gross overload), Delco can quickly determine the quality level of a particular lot of reeds.

Better Fatigue Properties

In addition to its finishing capabilities, the Harperizer imparts high compressive stresses to the parts being finished. This compressive stress, when combined with general radiusing and surface finish improvement, boosts the parts' fatigue strength and resistance to cracking by removing surface imperfections that could be the starting points for fatigue failure.

Delco engineers have found that this compressive stress is consistent from part to part and from lot to lot. There are other ways of imparting compressive stresses to parts, but many of them do it at the expense of surface finish; not so with this process.

Although the first Harperizer that Delco purchased was aimed at solving the finishing problem associated with the R-4 reed, this machine and the five purchased since then have been used to process a variety of other parts, also. Often the machines have been pressed into service to finish parts needed yesterday for final assembly operations. Some of these parts have been completely processed in as little as 15 mm.

Ultimately, the genuine value of the machines to Delco lies not so much in the solution of an immediate problem but in the expanded capability to solve any future finishing problems.