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Automation of a Glow Discharge Spectrometer

David DeHaro, Eric Montejo-Francisco, Louis King, Micah Cerros

Department of Mechanical and Aerospace Engineering

University of California San Diego

Sponsored by Professor Kenneth Vecchio

Overview

• Professor Vecchio’s lab focuses on advanced material discovery through a High-Throughput Rapid Experimental Alloy Development methodology [1]
• Confirm metal alloy composition using a LECO Glow Discharge Spectrometer (GDS900) (Fig. 1a)

Objective

• Automate GDS measurement of the “spokes” of a wagon wheel sample (Fig. 1b) to increase efficiency of alloy development.
• Positioning ≤ 0.5mm precision
• Easy calibration and error handling by the user

References:

[1]Vecchio, Kenneth S, et al. “High-Throughput Rapid Experimental Alloy Development (HT-READ).” Science Direct, Acta Materialia Inc., 29 Sept. 2021

[2]LECO Corporation. “Glow Discharge Atomic Emission Spectrometer.” Elemental Analysis, 2024.

Acknowledgments:

We would like to thank Professors Jerry Tustaniwskyj and Marko Lubarda for the mentorship through the project, Professor Kenneth Vecchio and Dr. Haoren Wang for sponsoring and supporting the project, as well as the engineering staff — Tom Chalfant, Steve Mercsak, Steve Roberts, Ed Pogue, and Ian Richardson — for their help and expertise in electronics, mechanical design and machining.

Fig. 1: a) LECO GDS900 Spectrometer[2]

b) Wagon wheel metal alloy samples

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Design Solution:

• 3-axis sample alignment gantry mechanism

Vertical (Z) Axis Assembly

• FUYU High Precision Ball Screw Linear Motion Guide
• NEMA 23 Stepper Motor
• Precision: 0.03mm per step

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Horizontal (Y) Axis Assembly

• NEMA 8 Stepper motor with built in lead screw
• Lead screw
• Precision: .003 mm per step

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Gripper Assembly

• Spring Loaded clamp arm; V-base for wagon wheel securement

a)

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b)

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Hardware Performance

• Aligns 8 spoke sample
• Moves to safe position for cleaning
• Full integration unsuccessful due to software issues

Impact on Society

• Automation of the GDS speeds up material discovery, giving researchers time to focus on other tasks
• Stronger and lighter alloys have applications in many industries (see below)

Future Improvements

• Improve pushing component into the machine
• Finalize integration and testing
• Automate sample calibration
• Integrate limit switches to avoid motor crashes
• Automate O-ring cleaning between sample readings
• Easier and/or automatic Sample loading onto gripper
• Handle 16 spoke wagon wheel/wider variety of sample sizes

Software (API) Architecture:

• Communication via ethernet
• API facilitates communication between LECO’s CornerStone and PLC that controls the Sample Alignment Gantry Mechanism
• State machine computational model
• Idle State, Calibration State, Analysis State (figure #)
• Commands GDS900 to load, analyze, and unload sample
• Vacuum error management

Electronic Components:

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Into the Machine axis

• NEMA 23 stepper motor
• Rack and pinion

Fig. 11: Precision and accuracy of the mechanism, assessed by creating an 70x70mm grid with points every 10mm.

Calibration Buttons

Fig. 3: Gripper Assembly CAD

Fig. 4: Vertical Axis Assembly CAD

Fig. 7: X-Axis Assembly CAD

Fig. 5 Horizontal axis assembly

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Fig.9: Graphic user interface( GUI) (left) & vacuum error message (right)

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GDS O-Ring

Vertical Axis

Horizontal Axis

Sample Gripper

Fig. 2: Final assembled mechanism

Fig. 8: Overall Design Solution Components

Fig. 10: System(Top) and PLC(Bottom) State Machine Diagram