Inkjet Printing and Inspection Machine

I. Project and Equipment Description

1. Project Name

PET Bottle Inspection System for Cap, Tamper-Evident Ring, Liquid Level, and Inkjet Code Verification

2. System Function

The system is designed for continuous in-line quality inspection of PET bottles. It monitors cap condition, tamper-evident ring integrity, product fill level, and inkjet printing quality. Bottles identified as non-compliant are automatically removed from the production flow.

3. Maximum Line Speed

Up to 60,000 bottles/hour

4. Applicable Bottle Material

PET

5. Applicable Bottle Volume

200 mL–2 L

II. Environmental and Site Conditions

1. Applicable Installation Elevation

5–3,000 m above sea level

2. Ambient Temperature

5°C–40°C

3. Relative Humidity

50%–65% RH

4. Installation Site Requirements

The customer shall provide an installation area with adequate floor flatness, structural strength, and load-bearing capability. The relevant site conditions shall meet applicable national standards to ensure stable and dependable equipment performance.

5. Storage and Preservation

Following delivery, the equipment, assemblies, and spare components shall be kept in a storage environment that meets the applicable requirements. For equipment stored prior to installation, appropriate lubrication, inspection, and preservation measures shall be implemented to protect against corrosion, deformation, and other forms of deterioration that may adversely affect subsequent installation, commissioning, or operation.

III. Utility Requirements

1. Electrical Supply

220 VAC, 50 Hz, single-phase

The electrical supply shall be arranged by the customer. Any special voltage or electrical configuration must be specified before equipment design and manufacturing. Changes to the standard power requirement may affect the technical configuration, production lead time, and final equipment cost.

2. Power Consumption

Approximately 2.4 kW

3. Control Power

24 VDC

4. Compressed Air

4–12 Pa

The customer shall be responsible for providing the compressed-air pipeline from the plant air source to the connection point of the main inspection unit.

Note: The compressed-air specification should be reconfirmed before final release. 4–12 Pa is unusually low for industrial pneumatic equipment and may have been intended as 4–12 bar or 0.4–1.2 MPa.

IV. System Configuration and Inspection Process

1. Installation Arrangement

The inspection system is designed for direct integration into the existing PET bottle conveying line. It shall be positioned at the specified inspection station according to the actual production-line layout and process sequence.

2. Defects to Be Inspected

The system can identify the following non-conformities:

• Cap missing

• Cap installed above the specified position

• Cap tilted or incorrectly seated

• Damaged or broken tamper-evident ring

• Insufficient liquid level

• Missing inkjet code

• Excessive or abnormal inkjet printing

3. Inspection Workflow

Step 1 – Bottle Registration and Position Tracking

As a bottle enters the inspection area, the positioning sensor detects its arrival and initiates the inspection sequence. The control system assigns a unique tracking ID to the individual bottle and links this ID with the encoder's position feedback.

This allows each bottle to be tracked accurately as it moves through the inspection and rejection sections.

Step 2 – Image Acquisition and Evaluation

The positioning signal is used to coordinate image acquisition. Cameras are triggered to inspect three designated areas of the bottle:

• Cap and tamper-evident ring

• Internal liquid level

• Inkjet-printed marking

The acquired images are transferred to the vision-processing unit for analysis. The inspection software evaluates the relevant characteristics according to the predefined quality criteria.

The resulting inspection status is displayed on the HMI (Human-Machine Interface) for operator monitoring and is simultaneously communicated to the PLC (Programmable Logic Controller) for subsequent control operations.

Note: Inkjet inspection evaluates the printed characters or marking on the bottle/cap, rather than the physical condition or operating status of the inkjet printer.

Step 3 – Automatic Rejection

If an inspection result is determined to be defective, the system records the corresponding bottle ID and continues to monitor its position using encoder feedback.

When the identified bottle reaches the rejection station, the PLC activates the reject mechanism at the appropriate timing. The rejector then removes only the corresponding defective bottle, while qualified bottles continue through the production line.

The complete process integrates bottle identification, image inspection, result processing, position tracking, and automatic rejection, allowing the system to maintain reliable quality control even at high production speeds.

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 inspection module utilizes three CCD cameras installed at different viewing angles to capture a comprehensive visual profile of each PET bottle, significantly reducing blind areas and enhancing inspection coverage. Specially designed optical lenses help minimize interference from ambient light and control light distribution, ensuring consistent and reliable image acquisition. The vision system is primarily used to identify cap-related defects, including missing caps, excessively raised caps, incorrectly positioned or tilted caps, and cracked, damaged, or otherwise defective caps.

8. Liquid Level Detection

This inspection module utilizes a CCD camera to obtain front-view images of the liquid level inside each PET bottle. During image acquisition, the bottle is kept stationary to maintain a stable and nearly horizontal liquid surface. The captured image is processed using a contrast-based vision algorithm, in which the filled portion below the liquid surface is represented in black, while the unfilled area above it is rendered in white. The system then analyzes the boundary between the two regions and compares its position with the predefined reference level to determine whether the actual liquid level is within the specified range or below the required threshold.

9. Inkjet Printing Inspection

This inspection module is equipped with a CCD camera for front-facing image acquisition of the inkjet markings applied to both the bottle body and cap. The captured images are processed through a dedicated vision algorithm to evaluate the printed content and identify missing, abnormal, or otherwise non-conforming markings. Once a printing defect is detected, the system automatically sends the corresponding rejection signal to remove the defective bottle from the production line. The module supports multiple color combinations, including black printing on yellow caps and white printing on black caps, providing reliable inspection under different marking conditions.

10. Detection accuracy