McDonnell Douglas Aerospace (MDA)-St. Louis has implemented Geometric Dimensioning and Tolerancing (GD&T) as a management tool to provide clear definition of product tolerances and maximize the use of acceptable tolerance values. When preparing to implement GD&T, the company established three goals:
Integrate GD&T application and interpretation with the Integrated Product Development teams and manufacturing processes through dimensional management.
In support of successfully implementing the GD&T program, MDA-St. Louis created extensive training courses, developed internal consultants and mentors, formed the MDA-St. Louis GD&T Committee, and provided a member to serve on national and international standards development committees. Basic and advanced training courses were developed, and over 1800 employees have received the training. The curriculum and training materials used were developed by MDA-St. Louis and include textbooks, student manuals, instructors’ manuals, and the models to demonstrate the instructions.
To help consistently interpret GD&T information, MDA-St. Louis also assembled internal consultants and mentors and published this list for each building. MDA-St. Louis also formed a GD&T committee to identify these internal consultants and mentors. This committee is comprised of people from different disciplines who review requests for clarification of the ANSI Y14.5M Standard and issue bulletins which provide information and policy guidelines.
MDA-St. Louis asserts that consistent interpretation of the requirements by manufacturing and inspection will provide cost benefits. Using GD&T in the fabrication of a bulkhead assembly led to loading the bulkhead into the assembly fixture in eight hours as opposed to the previously required 3 days. With the use of a fully functional tolerance zone, there is increased tolerance without reduced quality. On one project, the use of shims was eliminated when attaching a leading edge extension assembly, which led to a savings in time and cost.
MDA-St. Louis has received significant results through its GD&T efforts and is continually updating the training, internal expertise, and materials to ensure that skill levels are maintained.
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