Inkjet Defect Detection Machine

Inkjet Printing, Liquid Level & Tamper-Evident Ring Inspection System

I. Project Overview

1. Project Name

Inkjet Printing, Liquid Level, and Tamper-Evident Ring Inspection System

2. Project Description

The proposed inspection system is designed for the automated quality inspection of PET bottles. It detects defects related to cap integrity, tamper-evident ring condition, liquid level, and inkjet printing quality. Any bottle identified as non-conforming will be automatically rejected from the production line.

3. Maximum Production Speed

Up to 60,000 bottles per hour (BPH)

4. Applicable Container

PET bottles

5. Applicable Volume Range

200 mL – 2 L

II. Environmental and Site Conditions

1. Installation Altitude

5–3,000 m above sea level

2. Ambient Temperature

5°C–40°C

3. Relative Humidity

50%–65% RH

4. Factory Site Requirements

The installation site shall provide adequate floor flatness, structural load-bearing capacity, and other necessary site conditions in accordance with applicable national standards to ensure reliable and stable operation of the equipment.

5. Storage Requirements

After delivery, the equipment and its components shall be stored in an environment that complies with applicable national storage standards. Appropriate lubrication, corrosion protection, and preventive maintenance shall be carried out during storage to prevent surface damage, corrosion, deformation, or other conditions that may adversely affect subsequent installation, commissioning, and operation.

III. Utility and Operating Requirements

1. Electrical Power Supply

220 VAC, 50 Hz, single-phase

Any special or non-standard voltage requirements shall be confirmed prior to order placement. Changes to the specified power supply may result in corresponding adjustments to equipment configuration, manufacturing lead time, and project cost.

2. Total Power Consumption

Approx. 2.4 kW

3. Control Voltage

24 VDC

4. Compressed Air Supply

4–12 Pa

The customer shall provide the compressed-air pipeline from the air source to the main equipment unit.

Note: Please verify the compressed-air pressure unit. For industrial inspection equipment, 4–12 bar / 0.4–1.2 MPa may be intended rather than 4–12 Pa.

IV. Equipment Functions and Inspection Scope

1. Installation Position

The inspection system shall be installed at the designated position in accordance with the overall production line layout and process requirements.

2. Inspection Items

The system is capable of detecting the following defects:

• Missing cap

• Raised or improperly seated cap

• Misaligned cap

• Damaged or broken tamper-evident ring

• Low liquid level

• Missing inkjet code

• Excessive ink coverage or abnormal inkjet printing

• Incorrect or defective inkjet code

3. Inspection and Control Principle

Step 1 – Bottle Detection and Tracking

As each PET bottle enters the inspection area, the positioning sensor detects the bottle and sends a trigger signal to the control system.

The control system assigns a unique identification ID to each bottle and synchronizes the ID with the encoder's real-time position information. This enables accurate tracking of each bottle throughout the inspection and rejection process.

Step 2 – Image Acquisition and Defect Analysis

Based on the bottle's position and encoder information, the triggering system activates the camera units to capture images at three primary inspection areas:

1. Bottle cap

2. Liquid level

3. Inkjet marking

The inkjet inspection focuses on the printed code/marking itself, rather than the operation or condition of the inkjet printer.

The captured images are processed and analyzed by the vision processing system. Inspection results are displayed in real time on the HMI (Human-Machine Interface) and simultaneously transmitted to the PLC (Programmable Logic Controller) for further logic processing and defect determination.

Step 3 – Automatic Defect Rejection

When a defective bottle is identified, the PLC associates the inspection result with the corresponding bottle ID and tracks its real-time position using the encoder data.

When the defective bottle reaches the rejection station, the PLC sends a rejection command to the automatic reject mechanism, which removes the identified non-conforming bottle from the production line.

This closed-loop process ensures accurate bottle tracking, reliable defect identification, and automatic rejection of defective products without interrupting continuous production.

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 images of each bottle, effectively minimizing blind spots. Equipped with specialized optical lenses, it filters light from multiple directions to enhance image clarity and acquisition efficiency. The system is designed to identify cap-related defects, including missing caps, raised caps, tilted caps, and damaged caps.

PET bottle capping images captured by CCD camera

8. Liquid Level Detection

This module uses a CCD camera to capture a frontal image of the bottle’s liquid level. It ensures that the liquid surface inside the container appears horizontally aligned when the bottle is at rest. Through image processing, the region below the liquid level is rendered black, while the upper portion representing the empty space of the bottle is shown in white. A specialized algorithm is then applied to distinguish whether the liquid level is above or below the preset threshold.

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

9. Inkjet Printing Inspection

This module uses a CCD camera to capture images of the inkjet printing on bottles and caps from the front. It then digitally analyzes the captured images and automatically and accurately rejects bottles with unqualified inkjet printing. It is compatible with both yellow caps with black ink and black caps with white ink.

Sample image recognition processing effect

10. Detection accuracy