Little, Thomas A., Ph.D., COE; Park, Hisup (1991, ASQC) Lockheed Missiles & Space Company, Sunnyvale, CA
This abstract is an edited version of the author's original.
The variability of machined parts is the combined variation of the fixture, perishable tooling, part material, machine tool accuracies, tool holder, and processing rates. In the past when quality problems have arisen, it has been arduous and time consuming to isolate the independent effects of the factors likely to contribute to the observed problem.
Lockheed has developed a systematic approach to isolate and statistically quantify machine tool variability as well as the components of process variation. Machine tool variability management system (MTVMS) is Lockheed's approach to production quality management for machined parts. Lockheed's system is an extension of methods developed by Texas Instruments.
MTMVS is comprised of three key elements: (1) non-cut test using a computer-controlled laser system, (2) cut test using a specialized machined part and coordinate measurement machine, and (3) daily process monitoring and control through statistical process control (SPC). The goals of MTVMS are to quantify variation, minimize and control variation, and to link machine tool variation knowledge into the design engineering function.
For each of the three areas, software has been developed or utilized to make data collection standardized, efficient, and automated. MTVMS methods have improved machine tool maintenance, process design, tolerance design, machine tool purchase and qualification, daily process management, and manufacturing shop loading.
Aerospace industry,Tool wear,Machinery,Manufacturing,Statistical process control (SPC)