Feedback control effects on dimensions and defects of H13 tool steel by direct metal deposition process

As a promising and novel manufacturing technology, laser aided direct metal deposition (DMD) process produces near-net-shape functional metal parts directly from the computer aided design (CAD) model. In-process feedback control has been recognized as a critical element to ensure the dimensional accuracy as well as near-net-shape production. Furthermore, process parameters should be delicately controlled to produce defect-free parts with superior mechanical properties. A closed loop real-time optical height control system has been implemented to achieve better surface roughness and dimensional accuracy within designed tolerance. In this article, effects of feedback control on dimensional accuracy as well as defects such as microcrack and void/porosity are investigated for H13 tool steel samples, and experimental results are summarized. The samples fabricated with/without feedback control and with various deposition patterns are compared and the effectiveness of feedback control system, arrangement of height control sensors, and threshold of the average laser power are discussed.