Mold-cavity draft

As with other mold operation process mold release agents are usually required because the plastic melt can adhere to the surface of the mold cavity. Molds with very little or no draft usually require a release agent. Like other molding operations, a textured cavity can provide a textured product surface. Most texturing of cavities is by chemical etching so it is important to use the appropriate mold material to create a particular texture. An effective release is needed at the parting line to aid in demolding. 

Draft angle usually zero, but 0.5-1 desirable on long extended surfaces, or if mold cavity is deep. Minimum section ranging from 1 mm for aluminum alloys and steels, 2 mm for copper alloys, but can be as low as 0.6 mm for some applications. 

Draft on the cavity wall such as 1° is recommended to facilitate product removal. Lower-shrinkage plastics like PC and PMMA requires l1 to 2°. Undercuts are possible, but they should be kept to a minimum. Making provisions for undercuts or no drafts usually requires higher mold costs because the mold will require action such as core pulls or splitting a mold to allow separation parallel to the undercut groove. This type of mold action usually requires additional cycle time thus increasing cost. 

Draft n. A shght taper in a mold wall, proceeding inward from the parting surface to the bottom of the cavity, designed to facilitate removal of the molded object from... 

Draft angle n. In a mold, the angle in the profile plane with its vertex at the bottom of the mold or cavity, between the side of the mold and the vertical plane. In most cases, 1° is adequate for smooth ejection of parts from the mold. 

Draft n A slight taper in a mold wall, proceeding inward from the parting surface to the bottom of the cavity, designed to facilitate removal of the molded object from the mold. When the taper is reversed, tending to impede removal of the article, the term back draft, or reverse draft is employed. In weaving, a pattern or plan for drawing-in. 

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