iTSSe TSS A D V A N C E D M A T E R I A L S & P R O C E S S E S | J U L Y / A U G U S T 2 0 2 2 4 1 iTSSe TSS uncontrolled “noise” within the thermal spray process and its effect on measurable inputs and outputs. Consider the acoustic monitoring system developed by Rolls-Royce Corp. in conjunction with Virginia Tech and the Commonwealth Center for Advanced Manufacturing (CCAM). This technology acquires audible feedback from the thermal spray system and analyzes it in real time. The acoustic monitoring system can accurately detect many different types of events in the thermal spray cell, including high or low gas flow rates, powder line leaks, port and nozzle wear, and pulsing in the powder feed and/or carrier gas. Another sensor has been developed to monitor the spray plume for visual changes, including variations in angle and intensity. Data from each of these sensors can be correlated to variables such as powder and gas feed rate, enabling a better understanding of the state of the thermal spray cell. Ultimately, the vision is to create a system capable of self-correction within prescribed limits to ensure output quality. By monitoring external attributes such as light and sound, a potential control system has been demonstrated (Fig. 3). Changes detected by acoustic and visual monitoring are fed back to a control algorithm that actively updates the internal processing parameters of the thermal spray cell to compensate for any fluctuations in the system. FEATURE 7 SUMMARY The journey to zero defects is about understanding the sources of variation and reducing or eliminating them from a controlled process. A focus on prevention, robust use of defect reduction tools, and increased use of process diagnostics are more essential than ever for eliminating defects and nonconformance from thermal spray processes. New tools and emerging technologies can be leveraged to create a manufacturing environment where thermal spray rework can be greatly reduced, resulting in cost reductions and shorter lead times for suppliers and OEMs. ~iTSSe For more information: Ann Bolcavage, engineering associate fellow – coatings, Rolls-Royce Corp., 420 S. Meridian St., Indianapolis, IN 46225-1103, ann.bolcavage@rolls-royce. com. References 1. A. Buthmann, Cost of Quality: Not Only Failure Costs, ISIXSIGMA, https://www.isixsigma.com/implementation/ financial-analysis/cost-quality-not-only-failure-costs/. 2. G. Mauer and C. Moreau, Process Diagnostics and Control in Thermal Spray, J. Therm. Spray Technol., Vol 31, p 818-828, 2022. Fig. 3 — Schematic illustration of digital control system sensors and linkages for enhanced control.
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