Flowrate Calibration of Coaxial Powder Feeder During Laser Additive Manufacturing

Abstract

The fabrication of metal parts is the backbone of the modern manufacturing industry. Laser Additive Manufacturing (LAM) is combination of five common technologies: laser cladding (LC), rapid prototyping (RP), computer-aided design (CAD), computer-aided manufacturing (CAM), and powder metallurgy. The resulting process creates part by focusing an industrial laser beam on the surface of processing work piece to create a molten pool of metal. A small stream of powdered alloy is then injected into the molten pool to build up the part gradually. By moving the laser beam back and forth and tracing out a pattern determined by a CAD, the solid metal part is fabricated line by line, one layer at a time. During LAM, the design and development of powder feeder is the critical technology of LAM equipment. During the synchronous powder feeding method, the machining quality mainly depends on the machining rate, powder feeding rate, laser power density, spot diameter and powder delivery speed. The powder feeding rate and powder delivery speed are determined by the delivery features of powder feeder. In the case of constant outlet pressure of throttling valve of gas bottle, with the increase of rotary speed of powder feeding disk, the pressure at the outlet of powder feeding pipe shows the upward tendency on the whole. The faster the rotary speed, the higher the pressure at the outlet of powder feeding pipe. It can be concluded from the changing rules of powder feeding flowrate at the different outlet pressure of gas bottle and rotary speed of powder feeding disk, in order to better realize the stable control of powder feeding flowrate, the outlet pressure of gas bottle should choose the middle grade. Then, the powder feeding flowrate could be precisely adjusted by controlling the rotary speed of powder feeding disk.1