Date of Award

2023-12-01

Degree Name

Master of Science

Department

Mechanical Engineering

Advisor(s)

David Espalin

Abstract

Lack of confidence in the quality of materials produced with metal AM has hinged on the unaddressed defects inherent to the process. Studies have worked to determine defect formation mechanisms and provide adjustments to key process controls. However, these advances have typically been developed in-house on research systems which offer increased and transparent control to the operator. A research gap exists in applying changes in approach of scan strategies to existing commercial systems, which can incentivize adoption while furthering development. The focus of this study is the implementation of inter-vector power ramping on a commercial laser powder bed fusion system to mitigate variability of melt-pool geometry in transient states. System specific kinematics were characterized and an analytical model based on normalized enthalpy was simplified to calculate power adjustments. Scanner encoder position data was monitored and used to derive velocity and acceleration for the test geometry. MATALB was used for data processing and to develop a nonlinear velocity approximation. A python script was developed to generate and visualize system compatible build files. Initial tests revealed inaccurate spatial/temporal positioning of the applied ramp, requiring modified power adjustment vector indexes to offset the ramp. Single layer plate scans were performed comparing constant and ramped power when accelerating. Laser and scanner monitoring data and surface measurements were used to verify scan strategy execution while depth measurements from micrographs of melt-pool cross-sections were used to quantify the ramp effectiveness. Initial results proved useful in identifying several limitations in data processing and the effects of hardware constraints on implementing functionality for advanced LPBF process control.

Language

en

Provenance

Recieved from ProQuest

File Size

155 p.

File Format

application/pdf

Rights Holder

Antonio York

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