Depth of Draw Ratio

The depth of draw ratio is defined as the ratio of the maximum depth of the female die and the minimum distance across the open face of the die at any given location on the die.

It is generally recognized that the Thermo Pressure Forming Process is at its best when the depth of draw ratio is less than 1 to 1. In other words, a part which is 12 inches across should not be more than 12 inches deep.

The depth of draw ratio can be increased by combining other more complex forming procedures with Thermo Pressure Forming. Plug-assisted, snap back and billow forming are common procedures used to increase the maximum depth of draw ratio. Parts with draw ratios of 2 or even 3 to 1 have been formed in special cases.