Product Design - Good Angle for Demoulding a plastic part...

Good demoulding angle is used to protect plastic part surface from scratch during ejection. It is a draft in demoulding reserved along with the ejection direction; some of these are shown in Fig.1-8. The good demoulding angle depends on the material shrinkage, part shape, wall thickness, and ejection location.

good demoulding angle

                                        Good demoulding angle needs good design. For inner holes on a plastic part, the smaller end of core is used as reference. Its  demoulding angle is shown along with the rising direction. For exterior of a plastic part design, the larger end of cavity is used as reference. Good demoulding angle is dimensioned along with the reducing direction. Please refer to Table1 for various good draft designs solution of demoulding angle.

 A typical good demoulding angle ranges between 30′~1°30′. Normally a tall or large plastic part design has a good smaller demoulding angle. When there is a special need or higher precision requirement, a smaller demoulding angle is used. Good external  demoulding angle can be as small as 5′.  Good internal draft can be as small as 10′ ~ 20′. A complex plastic part, which is difficult to eject, should adopt a larger demoulding angle.

                                           Usually a good demoulding angle of 4°-5° on each side is considered for a plastic part design with ribs or bosses. Good larger demoulding angle should be chosen for a plastic product with large wall-thickness; during mold opening, in order that the product id retained on the side of the moving mold, demoulding angle  of the inner surface should be smaller than that of the outer surface and the other way round, good demoulding angle of the outer surface should be smaller than that of the inner surface so as to retain the product on the side of the fixed mold.

For flat cavities, good demoulding angle of 0.5° is sufficient.