Meaning
The industrial process of increasing the linear velocity of a substrate during production translates laboratory coating results into high volume output. Successful web speed scale-up requires maintaining coating stability and drying efficiency at higher throughput rates. It is the transition point where the physics of the coating bead and the capacity of the oven are tested.
This process often reveals defects that were not present at slower speeds.
Throughput Acceleration
Moving from a ten meter per minute pilot line to a sixty meter per minute production line changes the fluid dynamics. The air entrainment at the coating head increases and the time available for leveling decreases. If the equipment cannot handle the higher speed, the web will vibrate and cause thickness variations.
Defect Threshold
Every coating system has a maximum speed where the film begins to break up or show ribbing. Identifying this limit is the primary goal of a web speed scale-up trial. Pushing past this threshold results in scrapped material and potential damage to the machinery.
The cost of calling the scale up complete before achieving the target speed is a lower production yield than the business model requires.
Drying Capacity
Increasing the web speed reduces the residence time of the coating in the drying oven. To compensate, the air temperature or velocity must be increased, which can lead to skinning or binder migration. The physical length of the oven often becomes the ultimate bottleneck for the entire manufacturing process.
A successful web speed scale-up demonstrates the capability of the line to produce high quality material at the design rate.
