In modern manufacturing, adhesive bonding is widely used for assembling plastic components, including sandwich-style structures. The quality of adhesive application directly determines bond strength, durability, and overall product reliability.
In high-speed production environments, ensuring consistent adhesive application becomes a significant challenge. Variations in bead size, placement, or temperature can lead to defects, reduced bonding performance, and increased rejection rates.
Process Characteristics and Measurement Challenges
In applications involving ribbed plastic sheets, adhesive is typically applied in continuous beads at elevated temperatures. The process is fast and repetitive, with parts being produced every few seconds.
However, maintaining consistent application quality is difficult due to:
• variations in adhesive bead size and placement
• high production speed limiting manual inspection
• temperature differences between adhesive and surrounding material
• need for repeatable and objective quality evaluation
Manual inspection using handheld infrared cameras may provide basic insight but is too slow and inconsistent for reliable process control.
Infrared Monitoring as a Solution
A fixed infrared camera provides an effective solution for continuous monitoring of adhesive application. By observing the same area of each part at a defined moment after production, it becomes possible to evaluate bonding quality in real time.
The key principle is based on temperature analysis:
• the adhesive bead has a significantly higher temperature than the surrounding material
• both adhesive and plastic surfaces have high emissivity, ensuring accurate IR measurement
• the average temperature within a defined measurement area correlates with bead size and application quality
Instead of measuring the exact geometry of the adhesive bead, the system evaluates the average temperature of a defined “adhesive zone”, providing a simple and reliable quality indicator.
Optris Solution: PI 640i and PIX Connect Software
A proven solution for this application is the Optris PI 640i infrared camera, combined with PIX Connect software.
Optris PI 640i
The PI 640i provides high-resolution thermal imaging, enabling precise detection of adhesive application.
Key features:
• resolution of 640 × 480 pixels for detailed analysis
• high thermal sensitivity for detecting temperature differences
• suitability for high-speed industrial processes
• flexible optics for different distances and object sizes
The camera can be installed at a fixed position (e.g., ~2 meters from the part), ensuring consistent measurement conditions for every production cycle.
PIX Connect Software and Process Integration
PIX Connect software enables advanced yet user-friendly analysis without the need for custom programming.
Key capabilities include:
• definition of measurement areas (e.g., adhesive zone)
• calculation of average temperature within selected regions
• alarm triggering based on predefined thresholds
• integration with external sensors for precise timing (e.g., photoelectric trigger)
• communication with PLC systems via analog or relay outputs
Using the Event Grabber function, the system captures thermal images at the exact moment after part ejection, ensuring consistent and repeatable measurements.
Quality Control Through Temperature Analysis
In practice, a reference temperature is determined through testing, representing correct adhesive application. For example:
• a defined average temperature indicates proper bead size
• lower temperature values signal insufficient adhesive
• automatic alarms can be triggered when thresholds are not met
This approach enables fast and reliable detection of defects without complex image processing or geometry measurement.
Advantages of Automated Thermal Monitoring
Implementing infrared monitoring in adhesive processes provides several important benefits:
• consistent verification of adhesive application quality
• elimination of slow and subjective manual inspections
• real-time detection of insufficient or misplaced adhesive
• simplified system setup without custom software development
• adaptability to different part sizes through optics and positioning
Additionally, thermal images can be stored and archived, providing full traceability of production quality.
Application Value in Industrial Production
Infrared-based adhesive monitoring transforms quality control from a manual task into an automated and data-driven process.
Manufacturers can:
• ensure consistent bonding quality across all produced parts
• reduce scrap and rework caused by application errors
• document production parameters for quality assurance and compliance
• improve overall process stability and efficiency
This approach is particularly valuable in industries with strict quality requirements, such as automotive, aerospace, and advanced manufacturing.
