Sensing and Perception are essential modules for any robotic welding and finishing system to sense, understand, and interact with the environment in real-time and productively. Sensors with complementary features will be distributed in workspace and be fused together to provide robust and reliable sensing for multiple tasks of interest in an automatic factories, which include local operations such as welding and finishing over a large space, and the interactions among robots, machines, humans and their environments. This project is to develop sensing and perception modules with the following main deliverables: (1) A software package which integrates different modules and devices for high resolution 3D reconstruction using low cost sensors. (2) Software packages to provide modules for inspection, process monitoring, and safety which are essential for welding and finishing. (3) Advanced robust sensing techniques for improved welding and finishing process control in uncertain and outdoor environments. We aim to provide key sensing and perception modules for improving the productivity of all stages of robotic welding/finishing, i.e., (i) pre-welding/finishing, (ii) intra-welding/finishing and (iii) post- welding/finishing. The perception modules will enable the robots to acquire information from environment and in turn adapt their actions to the changing environments, thus enhancing the productivity by enabling the fully automatic process.