13.1 Project Proposal

Introduction

Cracking an egg is a simple task for most people, but for individuals with physical impairments or limited dexterity, it can be difficult and frustrating. The process requires precise coordination and controlled force to avoid shell fragments mixing with the egg contents. This challenge extends to various situations, including professional kitchens, where speed and consistency are critical, and for individuals with disabilities who struggle with fine motor skills.

Automating the egg-cracking process would not only make cooking more accessible but could also improve efficiency in large-scale food preparation. A well-designed mechanism would ensure a clean and consistent egg-cracking experience, eliminating the hassle of picking out shell fragments and reducing waste.

Problem Statement

The primary challenge is to crack an egg cleanly and separate the yolk and whites without contaminating them with shell fragments. This requires precise motion control and force application. Improper handling can lead to crushing the shell, breaking the yolk, or failing to fully separate the contents.

Several mechanical complexities must be considered:

Variable Egg Sizes and Shapes: The mechanism must adapt to different egg sizes without requiring adjustments from the user.
Secure but Gentle Grip: Holding the egg firmly enough to prevent slipping but without applying excessive force that would crush the shell.
Controlled Crack and Separation: The force and motion applied to crack the shell must be just enough to split it, without shattering it into small pieces.

These factors make the problem non-trivial, as a simple single-axis joint or rigid clamp would not provide the necessary adaptability and precision. Instead, a mechanism involving multiple degrees of freedom and coordinated motion is needed to achieve a reliable egg-cracking motion.

Mechanism

The proposed mechanism would automate the egg-cracking process by following a three-stage motion sequence:

Grip and Hold: A set of soft or adaptive gripping arms would secure the egg in place. The grip must be firm enough to hold the egg but not crush it.
Crack: A controlled impact or slicing mechanism (e.g., a small blade or pressure-based fracture point) would apply force at a predetermined location to initiate the crack.
Separation: The gripping arms would then rotate outward or slide apart, pulling the eggshell halves apart while allowing the contents to drop into a bowl.

The design could incorporate:

Compliant gripping mechanisms (soft robotics or flexible material-based grips) to handle different egg sizes.
A guided cracking mechanism, ensuring consistent force application.
A secondary yolk separation module, which could be activated if needed for recipes that require only egg whites.

The proposed mechanism would include a slider-crank mechanism connected to a rack that is interfaced with two pinions. These two pinions have the arms holding the egg attached to them allowing the arms to rotate as the slider moves back and forth. In addition, a cantilever arm will be attached to the rack that helps push the egg down onto the blades before the holding arms rotate outward to allow the yolk to fall through. This mechanism would only involve one actuator in the form of a simple step motor.

Proposed Scope

The goal for this project is to develop a functional prototype capable of cracking and emptying an egg without shell contamination. The key tasks will include:

Analyzing the forces required to crack an egg cleanly.
Designing a gripping mechanism that can handle eggs of various sizes.
Developing a controlled cracking mechanism, ensuring repeatable and clean separation.
Building and testing a working prototype; iterating on the design based on performance.

If time permits, we may explore adding a yolk separation function, but the primary focus will be on creating a reliable egg-cracking mechanism. Future improvements could include automation features, optimizing for commercial applications, or integrating adaptive control for handling eggs of different strengths and shell thicknesses.

This project ties into interests in robotic gripping, food technology, and accessibility solutions, offering a practical application of mechanism design principles to a real-world problem.

Preliminary Design

The preliminary design includes a slider-crank mechanism driven by a motor mated with a rack and double pinion “4-bar”. The output slider motion from the slider-crank mechanism is the input for the rack and pinion 4-bar. In essence, the rack is the slider. The purpose of the gears is to attach arms holding the egg to the gears so that a natural rotation motion of the arms is created to crack the egg and dump the yolk. This system as a whole, by the Gruebler equation, has 1 degree of freedom. The slider-crank mechanism will be Grashof in order to allow the motor to make a full rotation. See the images below fora sketch of the design, the kinematic diagram of the system, and the Gruebler classification.