| Summary: | 碩士 === 長庚大學 === 機械工程研究所 === 91 === Abstract
Manual gas tungsten arc welding (GTAW) is still widely used in industry even for its numerous drawbacks, including inconsistent welding quality control, high labor cost, inadequate supply of skilled welders, and hazardous to human health, etc. Therefore, developing techniques and equipment for automatic GTA welding has been one of the most important topics for decades.
Automatic welding has some advantages over manual welding including consistent weld quality, higher productivity, easier training and longer welding production period for operators, etc. In order to achieve automatic seam tracking during GTA welding, various mechanical and visual controlling systems were developed and their limited applications in industry were due to costly equipments, higher precision requirements for weld joints, and difficulty in maintenance.
The objective of this research was to develop a reliable, simple and inexpensive weld seam tracking control system for automatic GTA welding process. The development of the automatic weld seam tracking system in this study was based on the relationship between arc voltage and arc length. Because the GTAW uses a constant current (CC) type power supply, increases in arc length results in the corresponding arc voltage increases. Consequently, the position of a weaving torch in welding a V-grooved joint can be predicted by the variation in arc voltage. This varying voltage signal can then be used for the seam tacking system, using a 8051 CPU program and stepping motors.
The experiments in this study focused on developing an automatic seam tracking system for the GTA welding and selected suitable parameters for welding plates and pipes. An automatic voltage control (AVC) system operating simultaneously with the torch weaving system was developed using the arc voltage signals as well. Welding experiments were conducted on welding of V-grooved butt-joint stainless plates to acquire proper welding parameters. In addition, welding of V-grooved butt-joint pipes was also conducted. By using a weaving arc with AVC control, the requirements of weld joint precision can be lessened significantly. Consequently, quality weld joints in plates and pipes can be successfully achieved by using the seam tracking system developed in this study.
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