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Capstone Project for my B.S. in Mechanical Engineering
Capstone Project for my B.S. in Mechanical Engineering
Project Context
In my final year of my B.S. in Mechanical Engineering, I completed my capstone project. I was the Project Manager for a team of 8 where I lead us through technical and logistical challenges for 9 months. Our team was paired with an industry client, through which we were given scope and technical specifications. Throughout the year, I lead client discussions for regular weekly updates, scope change, technical iteration when design changes were needed, formal presentations and reports, and communication of project schedule and challenges. My client, Wabtec Corporation, was looking to automate, decrease cycle time, and increase precision in the train bearing inspection process. My project was to automate the train bearing inspection process, indicating whether the bearings can be re-used or need to be remanufactured for future use in the client's product.
The full machine was 15' long and 3.5' wide. Intended to be in a warehouse to inspect multiple train bearing assemblies.
Each bearing is inspected for out-of-roundness (OOR) and surface defects employing two independent measurement systems.
Presenting my poster and machine at the engineering college expo in May 2024.
Technical Achievements
When the inspection is done by hand, the process takes up to 10 minutes per bearing. With the automation machine my team built, 5 pre-loaded bearings can each be inspected in under 5 minutes with minimal operator interaction. I designed the machine to accommodate two different bearing variants: one assembly being 12" diameter and 25lbs, the other being 14" diameter and 70lbs. Each bearing is measured for out-of-roundness with precision of 0.0001” and surface defects of ≥0.003”. The client’s goal was to put this device in an active and bustling warehouse where operator safety and ease of use were critical in the machine design.
Bearing Path Through Device
Machine Breakdown by Sub-assembly
Loading Conveyor - The operator can load up to 5 bearings of the same type. The off-the-shelf conveyor will move them forward, stopping at the end and uses 2 end pieces to align the center of the bearing to the conveyor. As the conveyor senses the moving bearing, the diameter can be found – determining which of the 2 bearing types is loaded.
3-Axis Dolly - The 3-axis dolly lifts 1 bearing at a time off the conveyor and will bring the bearing through the 2 measurement systems. Movement along the x-axis brought the bearing through the main machine. The bearing could be raised and lowered with the y-axis controls. Sensors could access the full circumference of the bearing by rotating about the c-axis.
Custom Calipers inspecting for OOR - These adjusting calipers measure the inner diameter and outer diameter (ID/OD) concurrently. A tension spring pulls two known points onto the OD of the outer ring while a compression gas spring presses two known points onto the ID of the inner ring. The ID and OD can be calculated based on the displacement of these known points. (See image and more challenges with this design below) The dolly rotates the bearing around the c-axis and the ID/OD are found at 6 points on the bearing’ circumference, determining out-of-roundness (as defined by the client).
Surface Defect Detecting Sensor - A Keyence laser profilometer was used to detect surface defects on the inner and outer surfaces of the bearing. Since the sensor itself was too large to fit in the ID of the bearing, I designed a (λ /4) mirror periscope-inspired assembly to scan the bearing’s surface. Multiple passes were needed to scan the full bearing surface.
Unloading Ramp - The bearing was then brought to the static unloading ramp designed to guide and slow the movement of the 5 unloading bearings. As the dolly moves the bearing to the unloading ramp, each bearing would be indicated as “Go” or “No-Go.”
Electrical Box (not pictured, on backside of device) - The electrical box contains the Programmable Logic Controller, sensor controller, power distribution, and more. While I did not work much on this sub-assembly as project manager, I was very involved in the electro-mechanical integration into the full machine.
Operator Panel (not pictured, removed to show internals) - The operator panel was built to both initiate/end the automation cycle and to help an operator in a troubleshooting scenario. Controls include: E-Stop, power, calibration, homing, jogging/movement of each axis, and measurement initiation.
Side profile of the ID/OD custom calipers. Bearing would be raised into this spring system from below, guiding the wedges to the outer and inner surfaces of the bearing.
Custom Calipers - Mechanical Design Challenges
The custom ID/OD calipers were particularly challenging to design. To accommodate for the multiple bearing sizes, I needed to have a ID/OD measurement system that had the range to span about 2” of variability in bearing size, but also the precision to measure within 0.0001”. Additionally, the centering system at the end of the conveyor was estimated to get within 0.25” accuracy and the large bearing had slack that was not nominal in our inspection – all of which requires more variability in the calipers. This took about 6 weeks of brainstorming, prototyping, and iterating to get to this final design. To learn more about how this system works and the design challenges, you can read sections 4.5 and 4.6 in the Final Report attached below.
If you're interested in learning more, I have attached my final design report at the bottom of this page. This report documented the design decisions, BOM, budget usage, final design, and manufacturing drawings created in the project. While writing, I had to keep in mind the two audiences: the client who sponsored the project and the student team that would continue with the scope over the following year.
CUBoulderMechanicalEngineeringTeam_23-24_Wabtec_FinalReport.pdfGoogle Sites
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