GMNA GMN11174 PDF

This document outlines a method to quantify the loose and loosely adhered foreign material in and on sand cast (i.e. greensand, precision sand, semi-permanent mold, and lost foam) blocks and heads ready for shipment to the GM final machining plant. Iron and aluminum castings are included. At a minimum, the final operation (foundry, heat treatment, painting, impregnation, or cubing/pre-machining) that ships the casting to the final machine plant is required to perform this test. The use of the test after any other operations is optional, but recommended, at least until there process is shown to be stable and capable.

Its purpose is to insure that the cleaning methods utilized before the part reaches the final machining source are operating correctly and removing excess foundry materials, heat treat quenching materials, cleaning media, premachining burrs, grinding burrs and any other foreign material that could overwhelm the machining plants' washers.

The method involves two steps:

1. Step one involves impacting the casting to loosen retained material, and then collecting the loosened material by manipulating/rotating the part to allow material to fall out of passages. Compressed air may be used to blow material out of the casting. Determine and record the weight of solids collected. (Foundry slang term - "Tunk" Test).

2. Step two involves a visual inspection of all surfaces of the part, documenting any potentially detrimental loosely adhered foreign material on the surface of the casting (i.e. burn-on, burn-in, core or pattern coating, fragile metal fins from core/mold misalignment, excess metal in the form of the EPS beads from lost foam cast parts, etc.) and comparing to a standard established for the specific part.

Note: Nothing in the specification supersedes applicable laws and regulations unless specific exemption has been obtained.

Note: In the event of conflict between the English and domestic language, the English language shall take precedence.