In situ monitoring of direct energy deposition via structured light system and its application in remanufacturing industry

Abstract

The Direct Energy Deposition (DED) process utilizes laser energy to melt metal powders and deposit them on the substrate layer to manufacture complex metal parts. This study was applied as a remanufacturing and repair process to fix used parts, which reduced unnecessary waste in the manufacturing industry. However, there could be defects generated during the repair, such as porosity or bumpy morphological defects. Traditionally the operator would use a design of experiment (DOE) or simulation method to understand the printing parameters' influence on the printed part. There are several influential factors: laser power, scanning speed, powder feeding rate, and standoff distance. Each DED machine has a different setup in practice, which results in some uncertainties for the printing results. For example, the nozzle diameter and laser type could be varied in different DED machines. Thus, it was hypothesized that a repair could be more effective if the printing process could be monitored in real-time. In this study, a structured light system (SLS) was used to capture the printing process's layer-wise information. The SLS system is capable of performing 3D surface scanning with a high-resolution of 10 µm. To determine how much material needs to be deposited, given the initial scanning of the part and allowing the realtime observation of each layer's information. Once a defect was found in-situ, the DED machine (hybrid machine) would change the tool and remove the flawed layer. After the repair, the nondestructive approach computed tomography (CT) was applied to examine its interior features. In this research, a DED machine using 316L stainless steel was used to perform the repairing process to demonstrate its effectiveness. The lab-built SLS system was used to capture each layer's information, and CT data was provided for the quality evaluation. The novel manufacturing approach could improve the DED repair quality, reduce the repair time, and promote repair automation. In the future, it has a great potential to be used in the manufacturing industry to repair used parts and avoid the extra cost involved in buying a new part.

Advancements in 3D Printing: Directed Energy Deposition Techniques, Defect Analysis, and Quality Monitoring

“…Structured light, on the other hand, provides detailed 3D models but requires controlled lighting and can be time-consuming and difficult to utilize for complex parts [147]. Though laser triangulation and structured light may be favourable in regard to the measurement of surface roughness, object size, and measurement accuracy, they struggle with highly reflective or absorptive surfaces, such as those found in finished metal AM [141,176,[206][207][208][209][210][211][212]. On the other hand, interferometry delivers high precision over small areas but is highly sensitive to vibrations and environmental changes [184].…”

High-speed 3D optical sensing for manufacturing research and industrial sensing applications

“…Researchers have already attempted to employ fringe projection for in-situ monitoring of additive manufacturing processes such as laser powder bed fusion (LPBF) [41,42,43,44] or direct energy deposition (DED) [45]. An example of using fringe projection for in-situ/in-process monitoring of a DED process by the author's research group [45] is shown in Fig. 3.…”

Vibration bending fatigue analysis of Ti‐6Al‐4V airfoil blades repaired using additive manufacturing

“…19 For AM parts, CT scanning has proven to be very useful in understanding the benefits, and consequences, of using AM for repairs. 20 Stress intensity factor (SIF) values are representative of the significance of the stress in each location, and it accounts for the consequences of having pores in these locations as well. 21 Similar concepts implementing SIF calculations have been proposed in fatigue life prediction approaches that examine the effects of pores on the fatigue life of an AM part.…”

“…Characterizing the pores in an AM part, before testing procedures occur, gives insight to information that would otherwise be completely unknown until the testing was concluded 19 . For AM parts, CT scanning has proven to be very useful in understanding the benefits, and consequences, of using AM for repairs 20 …”