Egg Grading Machine

Overview

An egg grading machine is a production-line system that automatically inspects, weighs, and sorts eggs into commercial size grades and quality categories before packaging. The machine handles 3,000–6,000 eggs per hour in a poultry facility or packing station. It is essential infrastructure in commercial egg production, replacing hand-candling and manual sorting.

The machine has three functional stages. The Feed Hopper & Intake receives bulk eggs from farm crates and meter them onto a conveyor. The Candling & Inspection Station uses high-intensity LED light and a camera to detect cracks, blood spots, and interior defects; defective eggs are diverted. The Weighing Unit then classifies eggs into four weight grades (extra-large, large, medium, small), and the Automated Packing Lane automatically places graded eggs into carton cells. The entire operation is orchestrated by a Control System & Logic running vision-based candling logic and weight-based diverter control.

Candling and defect detection

The Candling & Inspection Station uses LED Light Banks shining cold-white light (6500 K, 1500–2000 lumens) through each egg. The light penetrates the shell and illuminates internal structures. A high-speed Image Sensor (line-scan or area-scan CMOS camera, USB interface) captures the backlit silhouette of the egg. The Vision Processor, running embedded computer-vision algorithms, analyzes each image to detect:

• Shell cracks: Dark lines in the silhouette indicating shell fractures
• Blood spots: Red or brown inclusions inside the egg indicating contamination
• Meat spots: Darker, larger anomalies from degraded blood
• Thin spots: Areas of the shell that appear lighter (reduced calcium)
• Floating yolk: Excessive yolk separation (indicates age or mishandling)

The camera operates at high frame rate (e.g., 100 fps) to match the egg conveyor speed. As eggs move past the light source, the processor acquires one or more images per egg. The decision, pass or reject, is made within 50–100 ms, and the egg's identity is carried forward in the control logic.

Standard egg quality grades are defined by the USDA or equivalent (e.g., Grade A: no cracks, no blood or meat spots; Grade B: small defects allowed). The Programmable Logic Controller stores grade thresholds and adjusts sensitivity via recipe parameters.

Weighing and classification

After candling, eggs proceed to the Weighing Unit, where they are weighed individually. Four Load Cell Scales (load cells, ±0.1 g accuracy) are mounted in the conveyor path, one for each output lane. As an egg passes over a load cell, the Weight Amplifier measures its weight instantaneously. The Programmable Logic Controller compares the weight to stored thresholds:

• Extra-large: > 70 g
• Large: 60–70 g
• Medium: 50–60 g
• Small: < 50 g

Based on the weight, the PLC commands a Divert Gate Actuator solenoid to route the egg to the correct packing lane. The diverter is a small pneumatic gate or chute that deflects the egg left or right onto the appropriate conveyor segment.

Packing automation

Each Automated Packing Lane is an independent assembly line that automatically places eggs into carton cells. The lane operates as follows:

1. An egg arrives on the main conveyor and is positioned over an empty Egg Cup / Cell (a molded plastic or paper cell).
2. A Packing Servo (24 V linear actuator) moves the cup directly below the egg.
3. A Release Valve (solenoid 3/2 valve) is pulsed, releasing the egg into the cup via gravity.
4. The servo retracts, positioning the next empty cup.

Packing rate is 4 eggs per minute per lane, so a 4-lane machine completes a 30-egg carton every ~7.5 minutes (180 eggs/hour in packing phase). However, the system is designed to operate continuously, with filled cartons removed and replaced with empty ones by human operators.

The Egg Cup / Cells are arranged in a carousel or linear array, moving incrementally with each packing cycle. Rejected eggs (from candling) are diverted to a separate tray, preventing rejects from entering the saleable product stream.

Control and operation

The Control System & Logic consists of a Programmable Logic Controller (industrial PLC with 16+ I/O) and a Vision Processor (PC or embedded vision controller). The vision processor receives images from the candling camera and runs defect-detection algorithms at real-time rates. It outputs a binary pass/fail decision and a quality grade code for each egg.

The PLC receives the quality grade, reads the weight, and commands the diverter solenoids to route the egg. All solenoids, conveyor motors, and servo actuators are controlled via 24 V logic outputs. An LCD Panel on the machine displays production statistics (eggs/hour, reject rate %, weight distribution histogram) and allows the operator to select a recipe (preset grade and weight parameters).

The system is networked via USB or Ethernet, allowing remote diagnostics and recipe updates from farm management software. Many machines log each egg's grade and weight to a database for traceability and statistical analysis.

Maintenance and reliability

The Conveyor Belt and Egg Cup / Cells experience wear from continuous motion and contact with shell residue. Belts are replaced every 200–500 hours; cups are replaced or cleaned after each production batch. The LED Light Bank should be cleaned weekly to prevent dust dimming the backlight; individual LED modules are replaced if they fail.

The Image Sensor is the most expensive component (USD 2,000–5,000). The camera must be focused precisely and kept clean; lens fogging from humidity requires a heated lens cover or dry-air blower.

The pneumatic system (solenoid valves, regulators, filters) is standard industrial equipment. Compressed air at 5–6 bar is the primary utility requirement, in addition to 3-phase power. The Emergency Stop button is hardwired to cut power to all solenoids, instantly stopping packing and diverting operations.

Economics and integration

A medium-capacity machine (6,000 eggs/hour) costs USD 30,000–50,000 and requires 2–3 operators (one loading hopper, one removing cartons, one monitoring quality). Over a 10-year life and 15,000 operating hours, the machine grades ~90 million eggs, lowering the grading cost to USD 0.0005–0.001 per egg versus hand-candling costs of USD 0.005–0.01 per egg. Modern farms integrate graders into a packing line: eggs flow from barn → washer → grader → cartoning machine → cold store, with minimal human intervention.