Inkjet printing visual inspection machine

I. Project Equipment Overview

1. Project Name: PET Bottle Inspection System – Cap, Anti-theft Ring, Liquid Level, and Inkjet Printing Detection

2. Project Description: The system inspects PET bottles for defects in caps, anti-theft rings, liquid levels, and inkjet printing, and automatically rejects non-conforming bottles.

3. Maximum Capacity: Up to 60,000 bottles per hour

4. Bottle Type: PET bottles

5. Product Volume Range: 200 ml – 2 L

II. Environmental Conditions

1. Optimal Operating Altitude: 5–3000 meters above sea level

2. Operating Temperature Range: 5°C – 40°C

3. Relative Humidity Range: 50–65% RH

4. Factory Requirements: Floor levelness, structural stability, and load-bearing capacity must comply with national standards to ensure proper machine operation.

5. Storage Requirements: Upon delivery, parts and equipment should be stored in compliance with national standards. Proper lubrication and maintenance must be performed during storage to avoid surface damage or deformation that could impact installation, commissioning, or normal operation.

III. Equipment Operating Conditions

1. Power Supply: 220V, 50Hz, single-phase (supplied by customer; special voltage requirements must be communicated in advance as they may affect equipment specifications, delivery schedules, and pricing).

2. Total Power Consumption: Approximately 2.4 kW

3. Control Voltage: 24 VDC

4. Compressed Air: 4–12 Pa (air connection from source to main unit provided by the customer)

IV. Equipment Overview

1. Installation Point: To be integrated into the PET bottle production line at an appropriate location.

2. Inspection Scope:

• Missing caps

• Over-height caps

• Misaligned caps

• Damaged or broken anti-theft rings

• Low liquid level

• Presence of inkjet printing

• Excessive inkjet printing

1. As each PET bottle passes the positioning sensor, the sensor detects its presence and activates the control unit, which records both the bottle’s unique ID and the real-time encoder signal.

2. The control unit then signals the camera to capture images at three inspection points: the bottle cap, internal liquid level, and inkjet marking. The images are analyzed by the vision processor, and results are sent both to the Human-Machine Interface (HMI) for real-time display and to the PLC (Programmable Logic Controller) to prepare for rejection of defective bottles.

3. If a defect is detected, the control unit matches the rejection signal to the specific bottle ID and instructs the rejector to remove that bottle from the production line.

4. Equipment mechanical components

5. Electrical composition of the equipment

6. Testing cabinet structure diagram

Capping liquid level detection (capping liquid level detection at stations one and three)

Inkjet printing inspection (station 2, single-camera inkjet printing inspection)

7. Cap Inspection

This module employs three CCD cameras positioned at different angles to capture bottle images, minimizing blind spots during inspection. Specialized optical lenses filter incoming light from all directions, ensuring high-quality image acquisition. The system is designed to identify cap-related defects, including missing caps, tilted caps, misaligned caps, and damaged or broken caps.

PET bottle capping images captured by CCD camera

8. Liquid Level Detection

This module uses a CCD camera to capture front-view images of the bottle’s liquid level. It ensures that the liquid surface appears nearly horizontal when the bottle is stationary. Through image processing, the area below the liquid level is rendered black, while the region above it, representing the empty portion of the bottle, is displayed in white. A specialized algorithm is then applied to distinguish whether the liquid level falls below or exceeds the preset threshold.

           PET bottle image captured by the camera                Processed liquid level detection image

9. Inkjet Printing Inspection

This module employs a CCD camera to capture front-facing images of the inkjet markings on both bottles and caps. The acquired images are digitally processed to evaluate print quality, and bottles with defective or non-compliant printing are automatically rejected. The system supports inspection for both yellow caps with black printing and black caps with white printing.

Sample image recognition processing effect

10. Detection accuracy