Circuit Board Ejector Mechanism

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from left to right: Jaime Ayala, Nikki Imanaka, Emily Chambers, Davis Hill
Sponsors Schweitzer Engineering Laboratories SEL
Team Name EZ-Ject
Duration Fall 2018 - Spring 2019
Faculty Adviser
  • Steven Beyerlein
  • Sarah Willis
  • Jonathan Richards
  • Sally Mei
Team Members
  • Jaime Ayala
  • Emily Chambers
  • Davis Hill
  • Nikki Imanaka

The goal of this project is to improve ergonomics for installation and removal of circuit boards in Schweitzer Engineering Laboratories (SEL) products.

Problem Definition[edit]


SEL designs, manufactures, and supports products and services ranging from generator and transmission protection to distribution automation and control systems. In most of their products, circuit boards are connected by spring clips at the back of the case. These clips cause a large frictional force on the board, making it difficult to install and remove the boards. With the current clips the force required to remove and insert a board is around 40lbs (total).


The scope of this project is to design a mechanism or system that reduces the necessary force to install and remove circuit boards from SEL products.


  • Research on existing mechanisms
    • Any ejection system (not restrictive to tray ejectors)
  • Decision Matrix
  • Material selection and cost analysis
  • Functional concepts, made using a variety of materials and methods
  • Longevity analysis for chosen production material
    • Fatigue testing
  • Working prototype using production material
  • Design validation testing results with various materials
    • Insertion force
    • Insertion cycles
    • Thermal and Vibration
  • Production implementation plan - proposed tooling method and supporting business case
    • 3D prototype if feasible
      • Mold and factor for plastic parts
  • Final report containing full information listed above with detailed design info, analysis and test results

Value Proposition[edit]

Project Value Proposition


  • Must pass SEL vibration testing
  • Must reduce user force to <5 lbs
  • Must be contained inside the chassis
  • Must not contact the circuit board

Project Learning[edit]


Over-center mechanisms
Over center latches used for wood work made from paint can lid clamps.

Over-center mechanisms

Preliminary Designs[edit]

Idea Number Description
Idea #1: Rails
fully inserted
semi-ejected (would need to pull card out)
Currently in development. The pins on the long arms would sit in rails on the tray and would be able to push and pull the tray in and out of the chassis.
Idea #2: Over-Center Mechanism
Over-center laser cut prototype
Currently in development. One end of the mechanism is attached to the chassis, while the other end fits into a slot that can engage and disengage with the tray to push and pull the tray in and out.
Idea #3: Screw Rod
Telescoping threaded rod
Currently in development. Threads would screw into nut at the back of the chassis, pulling the tray with it. The handle telescopes to give greater ease of access and clips into the bottom of the tray when collapsed.
Idea #4: Slot Arm
Slot arm(closed)
Slot arm(open)
Currently in development. Arm would be attached to back of chassis. The arm would engage with the pin attached to the tray and pull it in. Future plans include adding spring return and movement stop to ensure the arm returns to an accepting position.
Idea #5: Y-lever
locked position
open position
Not currently in development, but may be a viable option. The Y-lever would hook on the wall-mounted pin and push and pull the tray in by rotating a bar at the front of the tray; thumb operated.
Idea #6: Peg slot
Not currently in development; may not be a viable option, but could be worth exploring. The pin would slide in a track on the tray, the pin itself is attached to a arm that slides on a rail. Downside to this design is the pin does not apply force to the center of the tray, which could lead to tray jamming.
Idea #7: Gears
Not currently in development; may not be a viable option, but could be worth exploring. The pinion would engage with the rack on the chassis and would move the tray
Idea #8: rubber
Not currently in development; may not be a viable option, but could be worth exploring. The rubber engages with the chassis wall and transfers movement to the tray
Idea #9: L-Hole
Not currently in development; flawed design, not functional as designed. The tray would be moved by pushing on the edge of slot in tray by rotating arm. Interference with chassis causes non-function.
Idea #10: Puzzle Piece
Not currently in development; flawed design, not functional as designed. Interlocking pieces apply force on tray on both insertion and removal. Tolerance necessities in design are higher than feasible limits.

Final Design[edit]


Design Validation Plan

Team Members[edit]

Member Discipline Email Hometown Responsibility
Jaime Ayala Mechanical Engineering Twin Falls, Idaho Meetings/ Organization

Jaime is 23-year-old Mechanical Engineering Student at the University of Idaho. He is originally from Southern Idaho where his family works on a farm. He plans on graduating from the University of Idaho with a Bachelor’s of Science in Mechanical Engineering. After graduation, he plans on working out in industry for a few years and work towards attaining his professional engineering license. Some of his hobbies are Motorcycle riding and anything else that goes fast. He is 100% reckless when it comes to riding his motorcycle and enjoys it a great deal.

Emily Chambers Mechanical Engineering Meridian, Idaho Budget/ Meeting Minutes
EZ-Ject emilypic.png

Emily Chambers is a senior in the mechanical engineering department, graduating in the spring of 2019. She grew up in Meridian, ID, often working with her father in the garage rebuilding a 1972 Chevelle. She enjoys working with solid modeling software to prove concepts before implementing them in the physical world. After graduation Emily plans to join industry, working towards an MBA and PE license. She is a member of the Vandal Marching Band, and in her spare time loves playing the piano and flute.

Davis Hill Mechanical Engineering Coeur D'Alene, Idaho Client Communications/ Wikipage

Davis Hill is a senior mechanical engineering student graduating with a B.S.M.E in May 2019. His academic interests include computer simulation and vehicle testing. After graduation he plans to work in an industrial environment, hopefully in a process manufacturing company. He also plans to receive an MBA and PE certification within 4 years of graduation. His hobbies include playing guitar, dabbling in analog circuits, fixing his ever-broken truck and spending time outdoors.

Nikki Imanaka Mechanical Engineering Kaneohe, Hawaii Team Leader
EZ-Ject NikkiPic.jpg

Nikki Imanaka was born and raised in Hawai'i on the Island of O'ahu. Nikki is a Mechanical Engineering student at the University of Idaho and a member of the Women's Swimming and Diving Team as a spring-board diver. She hopes to gain designing and possibly quality assurance experience in the work force upon graduating in May 2019 with her B.S.M.E. Nikki considers herself adventurous and loves trying new things. Some of her hobbies include surfing, hiking, hunting, art, diving, piano, and more. She is a visual learner and loves working with her hands to create physically real ideas. Through her passion to learn, she is excited to be working on her CSWP-Adv certificates, gaining shop experience, and to be taking a beginning welding class next semester!

Additional Documentation[edit]

Project Schedule

Gantt Chart

Meeting Minutes

Meeting Minutes

Informal Design Review
Formal Design Review

Client Interview

File:EZ-Ject Client Interview 9-14-2018.pdf