Original Date: 04/20/1998
Revision Date: 01/18/2007
Information : Manufacturing Confidence Evaluation
ITT Aerospace/Communications Division (A/CD) developed the Manufacturing Confidence Evaluation (MCE) process as a way to tailor manufacturing screening used during production. This approach obtains the greatest benefit for a level of expenditure, and precipitates workmanship and manufacturing defects as early as practical in the production cycle. Previously, the company used a non-tailored, contractually-required Environmental Stress Screening (ESS) process within its production cycle. The company performed this standardized process at three manufacturing levels: Level A (board level); Level B (module level); and Level C (finished unit level). Despite running a three-level ESS, ITT A/CD still found manufacturing defects present at the highest level, which indicated ESS (as specified by the contract) was not effectively precipitating enough defects.
MCE is a highly-tailored version of ESS. The process is driven by specific hardware needs and product/process maturity, and seeks buy-in from the customer. In developing MCE, ITT A/CD used quality methods (e.g., Taguchi design-of-experiments) to determine the most effective number of cycles and temperature ranges for thermal shock testing. An ESS Level A profile consists of 20 thermal shock cycles, unpowered, five minute dwell, and a -75°C to 85°C range. After extensive analysis, the company modified the profile’s parameters to 15 thermal shock cycles, five minute dwell, and a -58°C to 103°C range, which precipitated more defects at Level A. By identifying defects at this lowest level, ITT A/CD realized an average loss reduction of $7.30 per circuit card assembly a significant reduction considering the high production quantity of these assemblies.
Through analysis, ITT A/CD also determined that Level B provided no additional value once Level A profile was tailored. This step was progressively eliminated as each module yield improved. As a result, the cycle time of modules decreased by more than 14 hours without adversely affecting end-item reliability and quality. A similar analysis reduced Level C’s cycle time by 16.5 hours on the receiver/transmitter and 30.7 hours for each vehicular applique.
By using the MCE process, ITT A/CD significantly reduced its cycle times and tailored ESS within the company’s production effort to receive the greatest benefit for a level of expenditure. In addition, ITT A/CD is applying the MCE process to other programs to improve the company’s production efficiency and further its competitive position.
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