Automating a robot cell welding process

Sammanfattning: Today, the importance of sustainable and effective energy usage is rapidly growing. SWEP International AB leads the manufacturing of brazed plate heat exchangers that offer effective heating and cooling applications used in a wide range of systems and industries. In their manufacturing process, stud bolts are manually welded onto the heat exchanger surface. A project to fully automate this process using an industrial robot has already begun at SWEP to increase the process productivity, quality, and repeatability. First, the robot uses an attached touch probe to measure points on the surface and sides of a heat exchanger to calculate a center reference point and account for any inclination. Then, the robot uses an attached weld gun to weld stud bolts onto the surface. The purpose of this bachelor thesis was to continue their project of creating a fully automated solution that will fully replace the manual bolt welding station in the future. The first objective was to study their existing semi-automated solution and perform quality analysis by testing different amounts of current, weld time duration, and shielding gas flow. A bend test, torque test, and visual inspection were then performed to understand how each weld parameter affects the weld result. From this, a suitable set of parameter values were determined. The positional accuracy of two different methods for calculating the center reference point was then measured. In these accuracy tests, it was seen that the tolerances were not being met. Improvements were made to both methods to increase their accuracy. Lastly, it was concluded which method should be used in the automated welding process. The welding unit that supplies the current and gas flow was then set up to measure and monitor the welding parameters to create a fail-safe system that stops the process if any parameter is measured outside its tolerance. A control structure was then implemented to operate the original robot program via PROFINET (industry standard for data communication over Industrial Ethernet). A programmable logic controller (PLC) and Human-Machine-Interface (HMI) were programmed in Siemens TIA Portal, and additions were made to the robot program in ABB RobotStudio. This created an automated solution for the bolt welding process where the HMI can be used to create a work order, create different bolt configuration recipes, control the program flow, and monitor the process. Finally, ideas were presented on how SWEP can further improve the positional accuracy, as well as ideas for future work to create a fully automated solution that is ready to replace the manual welding process used today in their production process.