Ensuring Optimal Bond Strength and Placement with Real-Time Adhesive Application Monitoring
Monitoring Adhesive Applications to Prevent Defects in Plastic Part Bonding
Challenge
Maintaining consistent adhesive application on ribbed plastic sheets is difficult due to high throughput, temperature variation, and the need for traceable, quantitative quality control without manual inspection.
Solution
A fixed thermal camera monitors the adhesive zone at a precise moment post-ejection, using average temperature measurements to assess bead consistency and trigger alarms if deviations occur.
Benefits
- Detects inconsistent adhesive application instantly during production.
- Reduces scrap and rework by ensuring correct bead placement.
- Enables traceable quality control for safety-critical industries.
- Cuts costs by avoiding custom software development.
- Speeds up integration into existing automation systems.
Inconsistent Applications of Adhesive on Plastic Components
Monitoring adhesive applications ensures product quality and reliability across various industries. Consistent and accurate adhesive application guarantees optimal bond strength. In manufacturing processes, real-time monitoring can help detect irregularities such as insufficient or excessive adhesive, preventing potential failures and costly rework. Monitoring adhesive placement helps maintain process efficiency, reduce waste, and ensure compliance with industry standards. Many companies in sectors like automotive, aerospace, and electronics, where the integrity of adhesive bonds directly impacts safety and functionality, particularly in the aerospace and defense industries, require documentation of adhesive bond quality. Some may need documentation on every part to verify manufacturing parameters months or years later.
An engineering firm specializing in custom automation equipment for various industries must develop a system for applying adhesive beads onto ribbed plastic sheets. The adhesive application needs to be more consistent, compromising finished product quality, consisting of two plastic sheets bonded together. Each 900mm long plastic sheet is ejected from the adhesive application system every three seconds. The adhesive bead is applied at approximately 170 °C, while the area adjacent to the bead is around 25 °C, varying with the ambient temperature of the manufacturing facility. The client has used infrared handheld cameras with some success, but the manual inspection process for ensuring consistent adhesive application needs to be sufficiently quantitative.
Ensuring Consistent Adhesive Application with Fixed Infrared Cameras
Thermal cameras enable continuous real-time monitoring, immediately detecting inconsistencies such as uneven application, incorrect curing, or overheating. They operate without physical contact, eliminating the risk of contamination or disruption to the adhesive application process. Infrared sensors facilitate thorough quality control by providing detailed thermal images and data.
To achieve consistent adhesive application throughout the day in this example, the best approach is to use a fixed infrared camera that observes the same area of the part at a precise moment after ejection. The size and location of the adhesive bead can be easily detected and measured with a long-wavelength infrared camera, with the quality of the adhesive application directly correlating to the area covered on the plastic part.
Measuring the exact physical area of adhesive would require significant custom programming, which is unnecessary for determining adequate application. Instead, a specific area on the part can be monitored, encompassing both the adhesive bead and the adjacent temperatures. The average temperature of all pixels in this measurement area can be used to assess the adhesive application, provided the camera captures and stores each image simultaneously after ejection, and the measurement area remains consistent. Testing has determined that an average temperature of 85 °C indicates an adequately sized bead. If the adhesive bead is smaller than acceptable, the average temperature will be lower than 85 °C, triggering an alarm.
The Event Grabber feature in PIX Connect software is utilized in this application as it will freeze an infrared image when input from a thru-beam photoelectric sensor is received by the Industrial Process Interface. A holdoff time of 1.5 seconds is set to allow ideal timing for capturing the temperature of the Adhesive zone.
The PIX Connect software can archive fully radiometric thermal images, allowing every pixel value to be measured in stored radiometric TIFF image files. The example images were captured with a PI 640i (640 x 480) using a 33° optic from 2m away, providing the detailed image quality required by the client. A mid-range resolution (320 x 240) would have been adequate for this application. Parts of varying sizes can be tested similarly by adjusting optics or working distance.
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