In-Situ Process Monitoring of Directed Energy Deposition Powder Flow to Detect Anomalies
Open Access
- Author:
- Moroney, Sheila
- Graduate Program:
- Mechanical Engineering (MS)
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 03, 2023
- Committee Members:
- Robert Kunz, Professor in Charge/Director of Graduate Studies
Edward William Reutzel, Thesis Advisor/Co-Advisor
Amrita Basak, Committee Member - Keywords:
- Additive Manufacturing
Directed Energy Deposition
In-Process Monitoring
Powder Flow Rate
Anomaly Detection - Abstract:
- Directed energy deposition (DED) is a category of additive manufacturing (AM) that employs one of a variety of energy sources, (such as electron beam, laser, arc) to melt and deposit either powder or wire feedstock to build up standalone features or resurface existing components making DED a practical option for repair. Laser based directed energy deposition (LDED) additive manufacturing process is attractive for repair because of the ability to tailor process parameters to effectively restore part geometry while using the least amount of energy necessary to limit residual stress, distortion, and degradation of the base material. The use of LDED to repair parts in the aerospace and defense industries has helped to reduce costs of replacement parts. Currently, however, LDED lacks the reliability of other manufacturing processes. Many researchers have developed methods to monitor key process parameters of the LDED process in-situ. However, few studies have focused on a method to monitor the powder flow, a parameter that is critical to the success of a DED repair. And none have related variations in powder flow directly to deposition geometry and quality with data collected in-situ. The work presented in this thesis presents methods to monitor the powder flow rate and spatial powder flow distribution below the nozzle exit. In-situ powder flow monitoring analysis methods are developed and used to identify anomalies in the powder flow from nozzle exit through the powder focal plane. The ability for the system to detect a powder flow anomaly that impacts deposition quality is validated by performing a set of experiments that show the effect of irregular powder flow on build height.