Cap and Liquid Level Inspection Machine

I. Project Equipment Overview

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

2. Project Description: The system inspects PET bottles for cap defects, anti-theft ring integrity, liquid level accuracy, and inkjet printing quality, and automatically rejects non-conforming products.

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

4. Bottle Type: PET bottles.

5. Filling Capacity Range: 200 ml – 2 L.

II. Environmental Requirements

1. Altitude: Optimal operating range from 5 to 3,000 meters above sea level.

2. Ambient Temperature: 5°C – 40°C.

3. Relative Humidity: 50% – 65% RH.

4. Factory Requirements: Floor flatness, load-bearing capacity, and other facility parameters must comply with national standards and meet the normal operating requirements of the equipment.

5. Storage Conditions: After delivery, components and equipment must be stored in environments that comply with relevant national standards. During storage, proper lubrication and maintenance are required to prevent surface damage or deformation that could affect installation, commissioning, and operation.

III. Equipment Operating Parameters

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

2. Total Power Consumption: Approx. 2.4 kW.

3. Control Voltage: 24 VDC.

4. Compressed Air Supply: Minimum 4 Pa, maximum 12 Pa (customer is responsible for connecting the air supply line to the main unit).

IV. Equipment Overview

1. Installation Location – To be determined according to customer’s production line layout.

2. Inspection Criteria:

• Missing cap

• High cap

• Crooked cap

• Damaged or broken anti-theft ring

• Low liquid level

• Presence of inkjet code

• Excessive or abnormal inkjet printing

1. As each PET bottle passes the positioning sensor, the control unit records its ID and the current encoder signal.

2. The positioning sensor then triggers the camera to capture images of the bottle’s cap, liquid level, and inkjet code. The image processor analyzes the captured data and sends the results to both the HMI for real-time display and the PLC control unit to prepare for rejection of defective bottles.

3. When the control unit receives a rejection signal, it instructs the rejector to remove the bottle corresponding to the recorded ID.

4. Equipment mechanical components

5. Electrical composition of the equipment

6. Testing cabinet structure diagram

Capping liquid level detection

Inkjet printing inspection

7. Cap Inspection

This module uses three CCD cameras to capture images of bottles from different angles, reducing blind spots. Special optical lenses filter light from all directions to ensure efficient image acquisition. Its primary function is to detect defective bottles such as missing caps, overhanging caps, crooked caps, and broken caps.

PET bottle capping images captured by CCD camera

8. Liquid Level Inspection

This module utilizes a CCD camera to capture frontal images of the bottle’s liquid level, ensuring the liquid surface appears nearly horizontal when the bottle is stationary. Through image processing techniques, the region below the liquid level is displayed as black, while the empty space above appears white. A specialized algorithm is applied to differentiate whether the liquid level is above or below the required threshold.

9. Inkjet Printing Inspection

In this module, a CCD camera captures frontal images of the inkjet codes printed on bottles and caps. The system then performs digital image analysis to automatically and precisely identify and reject bottles with defective or missing inkjet printing. The inspection is compatible with multiple color combinations, including black ink on yellow caps and white ink on black caps.

Sample image recognition processing effect

10. Detection accuracy