Skill-Informed Putty Coating with a Force-Controlled Robot Arm on Cast-Like Surfaces

The manufacturing industry is currently facing a significant labor shortage, particularly in manual and skill-intensive processes such as putty application in sheet metal painting. This step is essential for creating smooth, defect-free surfaces before final coating, and typically relies on the expertise of skilled technicians to ensure consistent material deposition and surface quality. However, the decreasing availability of trained workers has created a pressing need for reliable and intelligent automation solutions. To address this challenge, a robotic system is proposed to automate the putty application process using a force-controlled robot arm. The proposed system captures and analyzes the motion characteristics of skilled human operators during manual application to extract key techniques and motion profiles. A force sensor is mounted on the robot end-effector to enable real-time feedback control, allowing dynamic adjustment of contact force and trajectory based on surface conditions. This adaptive control strategy ensures stable and even putty deposition across varying surface geometries. To evaluate the effectiveness of the proposed system, we conducted a series of experiments on curved and planar metal surfaces that mimic cast-like surfaces. The results demonstrate that the robot can achieve layer thickness uniformity and smoothness comparable to skilled work, while improving material efficiency and repeatability. The proposed approach contributes to the development of intelligent robotic finishing technologies and offers a practical solution to labor shortages in automated surface finishing and offers a feasible pathway to addressing skilled labor shortages in industrial settings. Future directions include extending the method to various putty types with distinct rheological properties and adapting to complex 3D surface geometries through enhanced sensing and control strategies.