Masters Theses


Shyam Barua


"Laser Metal Deposition (LMD) has been used as an additive manufacturing process in industries such as aerospace and die castings. LMD is especially useful in repair applications involving die repair. However, it is still not used widely in industry due to variations in the quality of parts. There are multiple interactions between various factors which influence the quality of deposit.

There exists a need for defect detection systems to detect any changes in the deposition quality during deposition. On demand detection enables adjustment in process parameters and minimization of rework cost.

Vision systems have been used extensively in the industry to observe high intensity processes such as laser welding, cutting and metal deposition processes. Due to the non contact nature of the sensor unlike thermocouples or other physical sensors, there is no degradation of the sensor.

In the first part of this thesis, a low cost vision system to observe the melt pool created by a diode laser is discussed. External illumination using ultraviolet light between 390-395 nanometer wavelength along with narrow band pass filters is used to illuminate the melt pool while blocking out the process radiation. A clear view of the melt pool is obtained and melt pool size measurements are obtained during laser scanning process.

In the second part of this thesis, a method of defect detection in LMD is discussed, wherein the deposited track behind the melt pool is the region of interest. A digital SLR camera is used to obtain images of the deposited track behind the melt pool wherein variation in temperature gradient on the deposited track is used to detect porosity and crack defects"--Abstract, page iv.


Liou, Frank W.

Committee Member(s)

Newkirk, Joseph William
Du, Xiaoping


Mechanical and Aerospace Engineering

Degree Name

M.S. in Manufacturing Engineering


Missouri University of Science and Technology

Publication Date


Journal article titles appearing in thesis/dissertation

  • Development of low cost imaging systems for LMD.
  • Vision based defect detection in LMD process


x, 62 pages

Note about bibliography

Includes bibliographical references.


© 2011 Shyam Barua, All rights reserved.

Document Type

Thesis - Open Access

File Type




Subject Headings

Pulsed laser deposition
Manufacturing processes -- Quality control
Manufactures -- Defects
Imaging systems -- Design
Image analysis

Thesis Number

T 10187

Print OCLC #


Electronic OCLC #


Included in

Manufacturing Commons