A minimum radius of .015" is required for mold depths of up to 2.5" Molds
with 2.5" to 5% depth require a minimum of 0.030" radius. A .060" minimum radius
is required for 6" to 10" depth. The deeper the draw, the larger the radius to
allow for a better material distribution. Please note that a 45 degree break at
corners is a clever way to prevent thinning of material also. Also recommmended is
that where 3 radii meet in a corner, that one of them should be as large as possible.
Male molds:
Radii should be a minimum of the starting gauge of the material . This allows
maximum material distibution and will reduce chill or flow lines. Pretextured material
is usually used on male molds and many varieties are available. Be aware that the
deeper the draw, the more distorted and "washed-out" the texture will be.
Draw Ratios:
Common draw ratios are on the order of 3:1 with the greater ratios achieved when
special attention to design and geometry are considered. We define draw ratio as the
surface area of the flat length and width of the sheet compared to the total surface
area of the flat length and width of the sheet compared to the total surface area of
the molded part. Note that the larger the ratio, the greater the difficulty to achieve
satisfactory wall thickness. This applies to male and female molds.
Undercut flanges:
Typically required in female molded parts, should not exceed a maximum of .375".
Ribs:
Formed in ribs should be space apart at least the height of the rib, and never
spaced less than the starting gauge of the material.
Female molds: