| Welding-based rapid prototyping is a newly developed technology ,which combines welding with a layered manufacturing method . In addition to its simple equipment ,low cost and high controllability, it can also melt a variety of refractory metals. Now it has become one of the most promising method to manufacturing high-quality and full-density metal parts . However , it still has a long way to improve the precision and performance of the compents made by such technology .So it is necessary to control the heat input and the amount of metal effectively .Our team has developed an automated system for welding-base rapid prototyping on the base of an Open-CNC system.We choose two different welding technology ,plasma arc surfacing welding and pulsed gas metal arc welding. The system can not only realize welding control independently,but also coordinate with the motion contral unit.So we can strike or extinguish arc automaticly ,then sampl various parameters and keep real-time control in deposition processing .This paper focus on the software and hardware design of the welding control system. This system use external analog control circuit to sample and control the analog signals ,such as welding current ,welding voltage ,wire feed speed and powder feed speed. Then choose PLC as the MPU to deal with the switching signals.We use FX1N Series PLC as the MPU of the welding control system to handle the switching signals come from PMAC and control cabinet panel ,then realize welding manual control and automatic timing control; use external analog control circuit to sample and on-line control some key parameters. Through the signal interaction between welding control system and PMAC, realize the synchronization of welding control and motion control .The software system is programed with GX Developer ,which is provided by Mitsubishi company. It realize the manual and automatic control in accordance with the requirements of timing logic of the welding technology.
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