Statistical Process Control Fundamentals in Packaging Substrate Converting
Statistical process control in substrate converting relies on sub-grouping across machine direction variance and isolating non-normal barrier defects.
Seal Integrity
Joint Durability
The strength and completeness of the bond between the sealed surfaces of a package prevent any leaks or contamination of the contents. Maintaining seal integrity is essential for food and pharmaceutical packaging, where the barrier against air and moisture must be absolute. This bond is achieved by applying heat, pressure, and time to the thermoplastic coating on the paperboard.
Testing Method
Evaluating the quality of the seal involves both destructive and non-destructive testing techniques. In the burst test, the sealed package is pressurized until it ruptures, which reveals the weakest point in the joint. Alternatively, a dye penetration test can detect microscopic pathways through the seal area that would allow gases to enter, ensuring that the packaging process is running within the specified safety limits.
These methods are used to establish the operating window for the packaging machinery, which helps operators identify when a heating element is failing or when the sealing jaws are misaligned before any defective packages are shipped to customers.
Process Validation
Consistent seal performance requires the continuous monitoring of the sealing parameters on the packaging line. Adjustments to temperature or dwell time must be made to compensate for any changes in the board thickness or coating weight. This control ensures that the package remains secure throughout the distribution chain.