Development and Optimization of a Spot Welding Robot for Battery Module Manufacturing

Sammanfattning

The rising demand for high-performance battery modules in sustainable energy applications has highlighted the importance of reliable and efficient manufacturing processes. This master’s project presents the design, implementation, and evaluation of a CNC-based resistance-spot-welding robot conceived for APR Technologies. The system integrates CNC-based motion control using GRBL, pneumatically actuated welding electrodes and a novel side-welding mechanism that rotates and lifts to access all sides of a battery module. A three-point calibration routine enables correction for module misalignment, while reed sensors on the actuators detect electrode sticking events, pausing operation. A multithreaded Python GUI, iteratively refined with operator input adds production tracking, real-time diagnostics, keyboard jogging, and a configurable settings panel. An external current sensor logs current and pulse duration for every weld, enabling in-process quality monitoring. Testing on a 154-cell dummy module with copper tabs demonstrated a sustained throughput of 1650 welds/h, surpassing the 1500/h requirement. In destructive peel tests, every weld that fell inside the 1.1–1.5 kA, 18–30 ms acceptance window withstood peel forces >10N, pulses outside this window were automatically flagged for review, confirming effective quality assurance. The side-welding mechanism produced joints of comparable strength while maintaining full-module coverage. While the system fulfils its functional goals, some limitations remain, including reliance on manual calibration and the use of a hobby-grade weld module with limited diagnostic capabilities. Future improvements should focus on automated, vision based calibration, the designing of a improved custom made weld module and on compliance with industrial safety standards. Overall, the project demonstrates the feasibility of a low-cost, modular welding solution tailored to the specific needs of battery module production.