Wrinkles are occasionally observed when using self-wound overlaminate films. Unfortunately understanding and troubleshooting the causes of wrinkles is a complex proposition. Any or all of the issues listed below may cause wrinkles during web handling.
- Gauge variation of the web
- Uneven roll tension (wind) from core to outer wrap
- Variations in temperature and humidity
- Roller misalignment and/or imbalance
- Long, unsupported web lengths
- Machine vibration
Presented differently, a web will always seek to align itself to be perpendicular to the roll it’s going over. If the web or part of the machine is skewed, the web can move laterally. Ultimately, this lateral movement of the web, or more precisely, lateral compressive forces generated by this movement is the central concept around how webs can wrinkle during any web handling process.
Observing the orientation of the wrinkle is the first step towards identifying its root cause: MD (machine direction), Diagonal or CD (cross direction). Each type of wrinkle has its own unique set of causes. MD wrinkles are related to web width. Diagonal wrinkles are indicative of alignment. CD wrinkles are rare but can occur in a roll due to interlayer slippage.
Over the next few months we will present various causes of wrinkles in more detail as well as actions that can be taken to resolve specific issues. The goal is to helps us all understand the factors that may play role in the formation of wrinkles throughout the value stream; including film production, adhesive coating and converting and even lamination.