Original Date: 07/21/2003
Revision Date: 01/18/2007
Best Practice : Plate Processing Statistical Process Control Program
Electric Boat Corporation, Quonset Point Facility automated many of its part manufacture and assembly processes. The company established a Plate Processing Statistical Process Control Program that validates the accuracy of water jet, plasma and laser cut parts, and the laser marking system to reduce assembly time and cost.
Electric Boat Corporation, Quonset Point Facility (EBQP) automated many of the part manufacture and assembly processes by feeding the detail design database (based on CATIA) into an advanced Plate Processing and Laser Marking System. The Plate Processing Statistical Process Control (SPC) Program allows plate processing personnel to monitor and track trends in the plate marking and cutting processes. SPC statistics are interpreted through the use of control charting of the measurements taken daily. A test coupon is cut at the start of each shift and a sampling of parts is tested. The data indicates when the equipment needs calibration and can be used to take out-of-tolerance equipment off-line until adjustments are made. This type of control chart management allows plate processing personnel to continuously produce parts that exceed design specifications, with a plasma cutting accuracy of ± 0.033”, a laser cutting accuracy of ± 0.005”, an abrasive water jet cutting accuracy from ± 0.005” to ± 0.020” (depending on material thickness), oxy fuel cutting accuracy from ±0.060" to ±0.125" (depending on material thickness), and laser marking accuracy of ± 0.005”.
Since the accuracy of the cutting and marking exceeds the design tolerances of the parts, EBQP can rely on its advanced automated systems, realizing overall reductions of 47% in per-part labor hours and 26% in structural fabrication labor hours downstream. Additional benefits of SPC include identifying the need for maintenance before operations are out-of-tolerance and fine-tuning the process.
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