Liquid Level Inspection

I. Project Equipment Overview

Project Title: PET Bottle Quality Inspection System – Cap, Anti-theft Ring, Liquid Level, and Inkjet Printing

Project Description:
This system is designed for online inspection and automatic rejection of PET bottles with defects related to bottle caps, anti-theft rings, liquid levels, and inkjet printing quality.

Maximum Capacity: Up to 60,000 bottles/hour
Applicable Container: Glass bottles
Product Volume Range: 200 mL – 2 L

II. Environmental Requirements

• Operating Altitude: 5 – 3000 m above sea level

• Ambient Temperature Range: 5°C – 40°C

• Relative Humidity: 50% – 65% RH

• Factory Conditions: Floor evenness, load-bearing strength, and other site parameters must comply with relevant national standards to guarantee stable operation.

• Storage Conditions: Upon delivery, equipment and spare parts must be stored according to national standards. During storage, regular lubrication and maintenance are required to prevent surface damage, corrosion, or deformation that may impact installation, commissioning, or operation.

III. Equipment Operating Conditions

• Power Supply: 220V, 50Hz, single-phase (provided by customer; special voltage requirements must be specified in advance, as they may affect specifications, delivery schedule, and pricing).

• Total Power Consumption: ~2.4 kW

• Control Voltage: 24 VDC

• Compressed Air: 4 – 12 Pa (air pipeline from source to equipment must be provided by customer).

IV. Equipment Description

1. Installation Position

The inspection system is installed at the designated section of the production line for continuous quality monitoring and rejection of defective bottles.

2. Inspection Scope

• Missing cap

• Over-height cap

• Misaligned/tilted cap

• Damaged or broken anti-theft ring

• Low liquid level

• Missing inkjet print

• Excessive inkjet print

3. Operating Principle

1. As each PET bottle passes the inspection point, the positioning sensor detects its presence and the control unit records both the bottle ID and encoder signal.

2. The sensor triggers the camera system to capture images of key inspection areas: the bottle cap, liquid level, and inkjet printing. These images are processed by the image processor, and the results are transmitted in real time to the Human–Machine Interface (HMI) for monitoring, while simultaneously sent to the control PLC for rejection logic.

3. If defects are detected, the control unit issues a command to the rejector, which removes the identified non-conforming bottle from the production line based on its recorded ID.

4. Equipment mechanical components

5. Electrical composition of the equipment

7. Cap Inspection
This module integrates three CCD cameras positioned at different angles to capture images of bottle caps, effectively minimizing inspection blind spots. Equipped with specialized optical lenses, it filters stray light from multiple directions, ensuring clear and precise imaging. The system identifies common defects including missing caps, over-height caps, tilted caps, and damaged caps.

8. Liquid Level Detection
A CCD camera is employed to acquire frontal images of the liquid level within the bottle. When the bottle is at rest, the liquid surface is expected to remain approximately horizontal. Through image processing techniques, the area below the liquid level is displayed in black while the area above appears white, facilitating clear differentiation. A dedicated algorithm is applied to accurately determine whether the liquid level falls above or below the predefined standard threshold.

9. Inkjet Printing Inspection
This module applies a CCD camera to capture frontal images of inkjet markings on both bottles and caps. The images are digitally analyzed to verify print quality, with defective bottles automatically removed from the line. The system supports different cap/ink combinations, such as black ink on yellow caps and white ink on black caps, ensuring high adaptability to varying production requirements.

10. Detection accuracy