PRODUCTIVITY GAIN IN WIRE ARC ADDITIVE MANUFACTURING BROUGHT BY ROBOT-INTEGRATED COOLING SYSTEM USING COMPRESSED AIR

Resumo

The international ISO/ASTM 52900 terminology classifies Wire Arc Additive Manufacturing (WAAM) as part of the group of Directed Energy Deposition (DED) of Additive Manufacturing (AM) processes for metallic pieces. These processes involve heat accumulation in some areas of a workpiece, which can possibly lead to thermal deformations, an excessively large weld pool and geometric defects. To avoid this, a common practice is the use of dwell times, where one stops the metal deposition and waits for the piece to cool down to a pre-determined temperature before resuming it, causing the productivity to plummet. The work presented in this paper studies a robot-integrated cooling system for WAAM applying compressed air, that shortens the dwell time needed to achieve a good quality piece using affordable and light equipment. Its goal is to assess the productivity gain attainable in the fabrication of a small (45 mm in height × nearly 50 mm in diameter) hollow piece of low carbon steel by WAAM using the forementioned cooling system. Experiments were performed and a simple mathematical model (avoiding the costs of Finite Elements models) to the essential heat transfer phenomena involved in the problem was put together and tested. The mathematical model overestimated the shortening of the cooling time, but the experiments confirmed the expected productivity gain, with the cooling system using compressed air allowing a 60 % reduction in the time needed to build a piece within acceptable geometrical tolerance limits.