Challenges With Metal Big Area Additive Manufacturing for Machine Tool Cross Beam Manufacturing

Two main pillars of modern manufacturing consist of subtractive and additive manufacturing (AM). Many of the challenges with subtractive manufacturing have been understood due to its maturity. Relatively, the AM space has many new challenges that are being explored. New designs, geometries, and features are explored to see the limitations of AM and what can be done in both design and manufacturing to increase the reliability of the process. This paper presents a case study of a machine tool cross beam that was designed for metal big area additive manufacturing (mBAAM) which was unable to be printed completely. The intent of the design was to additively manufacture a structure that could replace an existing crossbeam of a computer numerically controlled (CNC) machine from Oak Ridge National Laboratory (ORNL). The replacement mBAAM structure was designed to be printed with the MedUSA robotic cell of ORNL. The MedUSA cell consisted of three robotic arms that simultaneously deposit metal via gas metal arc welding (GMAW) onto a rotating table that served as the print bed. The mBAAM cross beam was approximately two meters by half a meter by half a meter with a mass of 673 kilograms consisting of mild steel. The failure of the print was due to significant distortion of the part which resulted in the termination of the print. Many factors contributed to the distortion of the part. Two main contributors to this part were residual stresses and the fixturing method for the print. The print failure demonstrated flaws of metal AM for large scale parts and what challenges need to be overcome for future large scale metal AM parts.