On surfaces in the direction of draw ie direction in which the mold opens, a minimum of 1° draft should be specified.
Draft in a mold facilitates part removal from the mold (see figure 1). When adequate draft is provided, the amount of part ejection mold features such as core pins or blades can be reduced, thereby reducing mold cost and mold complexity. Draft is particularly important on the inside of a part since plastic shrinks down around and grips the core (male part of the mold) as it cools.
Draft on certain surfaces of a part design results in improved mold shutoff surfaces (see figure 2).
Amount of draft on a textured surface should be more than the minimum. Allow 1° additional draft for each 0.001” in depth of texture. This increase in draft is needed to avoid scuffing of the molded texture during release of part from the mold. Guidelines for additional draft are available from various mold texture suppliers.
Helps with part ejection
Figure 1. Draft Prevents Damage to Part During Removal
Minimizes tool wear and potential flash with telescoping shutoffs
Figure 2. Draft Prevents Excessive Tool Wear on Sliding Components
Did you know?
Tapered draft also creates a dimensional change to your part. A draft of 1° creates 0.017” of taper per inch of part length (see figure 3 and Table 1).
Figure 3. Typical Drafted Part
Table 1. Dimension Difference of Drafted Part at Various Draft Angles
