Date of Award

2024-12-01

Degree Name

Master of Science

Department

Mechanical Engineering

Advisor(s)

David Espalin

Abstract

Additive manufacturing (AM) has been a maturing technology that has expanded over the course of the last decade in major advancements especially in accessibility, process monitoring, modeling, and stock material design. As its industry use is growing, the demand for added improvements such as multi-functionality increases, such as with a hybrid system that allows for modification of printed parts with different electrical components like the Foundry Multi-3D system. The system's purpose is to create AM parts with multifunctional electrical components with the vision to expand to other areas of interest in manufacturing such as ISAM. This work explores the use of one process in the Foundry system, laser soldering, by utilizing spectral pyrometry in a feedback control system that can be used to control temperature and detect defects. Laser soldering in hybrid additive manufacturing has yet to be fully studied regarding process development and control, but in the case of printed circuit board industry this process has been studied. This work utilizes the Hybrid AM process to create specimens containing 22- and 28-gauge wire in top-down solder joints. These joints were created using a PID temperature control system to reach a temperature of 280°C followed by a cooldown stage. During the soldering process, both laser output and temperature data were collected along with camera video and its respective image processing data for burning. Through temperature vs power plots, signal to noise ratios, and frequency analysis, soldering events can propagate through disturbances in temperature. The temperature vs power relationships show that the power requirements for 22-gauge wire is nearly twice of that of the 28-guage (7.94 Watts and 4.07 Watts respectively), and due to the design where joint locations have different heat paths, there is over a 1-Watt standard deviation for both gauge wires. From power requirements and thermal capacitance, it was identified the process can be scalable. The effect of thermal capacitance is seen through heating and cooling phases where some hysteresis occurs, this is more pronounced from the 22-gauge wire as it has larger thermal mass. Signal to noise ratios shows high amplitude peaks can relate to burning and wire movement, the difference between can be identified through the temperature where burning is seen more than 300ºC. The frequency analysis showed subharmonics peaks to the control frequency (333 Hz), where 29 Hz and 58 Hz showed relatively high peak disturbances. A narrow pass filter was applied to the temperature signal to identify possible disturbance peaks between both frequencies, and possible trends that occurred. From the 29 Hz signal, there were some peaks identified for burning, wetting, and phase change, however the peaks amplitude was inconsistent through other joints. This work identified that further control implementation to account for wire size heating requirements and thermal capacitance (through lead-lag functions) would be necessary to scale to other wire sizes. The signal to noise ratio and frequency domain can be used to identify certain events, however further refinement or advanced techniques would be necessary for better confidence in event detection.

Language

en

Provenance

Recieved from ProQuest

File Size

114 p.

File Format

application/pdf

Rights Holder

Alexander P Pustinger

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