Design Course
Designing of Plastic Products for Injection Moulding
Manufacturing Methods and Technologies
by
Draft
Draft is defined as a taper given to the walls of plastic parts in direction of line of draw to facilitate the easy removal of the part from the mold. Since plastic parts shrink as they cool they grip core of mold tightly. Without sufficient draft normal ejection from mold will be difficult. The value of draft depends on surface finish on the mold. A polished mold requires less draft than anunpolished mold.
Design considerations
- 0.25 degrees to 0.2 degrees per side for both inner and outer wall for untextured surface.
- For textured surface add 1 degree draft per 0.001 inch depth of texture.
