Rotomolders meet military Q-C specs.
As a prime U.S. military contractor, A.M. General Corp., South Bend, Ind., imposes stringent quality-control standards on itself as well as its vendors. The company, which supplies all-purpose "Hummer" military tactical vehicles to the U.S. Army, says that its adherence to q-c standards enables it to meet the government's demanding 98% acceptance requirements. The pay-off, says the company, could be seen on the grueling Saudi Arabian desert during the recent Persian Gulf conflict, where thousands of these vehicles were deployed. Here's a look at how q-c works in one supplier chain, and what it demands of two subcontractor rotomolding companies.
A.M. General is certified under the government's Contractor Performance Certification Program, under which the Army measures a series of goals and accomplishments and then progressively tightens the requirements. To ensure that it maintains its certification, the company has boosted its vendor quality surveillance and reviews. To this end, it instituted a Vendor Qualification Process. Under this procedure, A.M. General assembles a survey team composed of individuals from purchasing, q-c, and engineering, and usually a financial professional as well, to conduct an investigation of each vendor and its operations.
Each vendor must meet quality-assurance specifications originally intended for the aerospace industry, which A.M. General imposes on itself to qualify its manufacturing operations prior to purchase of an order. In keeping with these standards, q-c technicians continually inspect incoming materials - even those of long-standing vendors. All must meet the government's requirement for documentation indicating that objective evidence and calibration are traceable to the National Institute of Standards and Technology (NIST).
Adds Hank Casimer, A.M. General's purchasing manager, "Vendors must have a military-specification type of q-c control system in place. Not only must they have such a system established, but we require proof that they use it."
Two vendors that have met these requirements are Pawnee Industries and Spin-Cast Plastics, which supply the surge tank and engine intake-manifold air horn, respectively. Both Pawnee and Spin-Cast mold parts from Vestamid nylon 12 rotomolding grade supplied by Huls America Inc., Piscataway, N.J.
At Pawnee's Rotational Molding Div. in Maple Plains, Minn., the first run of each new design is submitted to A.M. General for inspection before the part actually goes into production. After the part is accepted, five q-c technicians monitor the entire rotomolding process - from incorporating the right amount of resin to heating and cooling.
Once the products are removed from the molds, they go to Pawnee's on-site laboratory for testing. Spot tests include freezing to determine cold impact resistance, tests for heating, air entrapment, and pressure, measuring the surge tanks' opening size and shape, and examining all screws. In addition, 100% of all surge tanks undergo thorough testing for leaks.
Spin-Cast in South Bend, Ind. check-weighs each piece after rotomolding in order to ensure that it is within proper tolerances. Upon cooling, a Spin-Cast technician conducts 100% visual inspection of each unit, paying particular attention to the size of the opening, which is very critical to the operation of the engine.
During processing, parts are inspected to be sure that they are distortion-free. Technicians also carefully examine the center piece to ensure that it is fully formed and nonporous. Each time a new processing run begins, technicians complete a thorough check in order to ensure that the molds are properly maintained.
Like A.M. General, both Pawnee and Spin-Cast in turn inspect their suppliers, recognizing that an essential part of quality control is selection of the best materials for the particular operation. For example, Pawnee selected Vestamid nylon 12 resin for its surge tanks only after determining through tests that its fine 35-mesh grind makes it more cost-effective and easier to mold than its alternatives, according to Pawnee's R&D engineering and tooling manager Thomas Zabel.
Other tests showed that it absorbed less moisture and was more stress-resistant. Spin-Cast's operations manager, Kenneth Clark, found nylon 12 to have a higher temperature resistance range than either nylon 6 or PE.
PHOTO : Rotomolded surge tanks and intake-manifold air horns, supplied by Pawnee Industries and Spin-Cast Plastics, must pass demanding quality standards to be incorporated into A.M. General's Hummer military vehicles.
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|Title Annotation:||Pawnee Industries Inc.'s Rotational Molding Div., Spin-Cast Plastics, quality control|
|Date:||Sep 1, 1991|
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