A multi-cavity tool can produce complete parts while still distributing material unevenly across the array. Center cavities may run thinner, edge cavities may retain excess stock, or one row may show a directional bias.
The causes include oven edge losses, cavity geometry differences, unequal plug penetration, sheet tension, manifold timing, and incoming gauge variation. The pattern can shift as the tool warms, making a startup setting unsuitable for steady production.
Map the entire array
Minimum wall thickness and part weight should be tracked by cavity position. Sheet temperature should be measured at corresponding locations before forming. A cavity-specific defect that persists after thermal balance is established points toward plug, vent, or geometry differences.
Pattern heating, local screening, individual plug correction, downholders, or revised array spacing may be required. Global changes should be avoided when only one zone is failing; they often improve one cavity while reducing the process margin elsewhere.