External draft can be as small as 5. Internal draft can be as small as 10 -20. A complex plastic part which is difficult to eject, should adopt a larger draft. Usually a draft of 4-5 on each side is considered for a plastic part design with ribs or bosses. Larger draft should be chosen for a plastic product with large wall-thickness; during mold opening, in order that the product is retained on the side of the moving mold, draft of the inner surface should be smaller than that of the outer surface and the other way round, draft 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 Fig 1-8: draft Table 1-3: drafts for common plastic materials Draft Draft Plastic Types Plastic Types Cavity PMMA PP&PVC-F 20′~50 PA PVC-U 50′~1°45′ 30′~50′ 30 ABS 30′-1°35′-1°30 1.2.6 Hole design k Holes may exist on a plastic part, including through holes, blind holes, screwed holes, and irregular shaped holes. In principle, holes should be as simple as possible. a complex hole increases the difficulty of mold making. As shown in Table 1-4, a sufficient gap should be reserved between holes or between a hole and the wall. The diameter of a hole also relates to its depth as shown in Table 1-5. When the distance between two holes or from the hole to the edge is smaller than the one specified in Table 1-4 please refer to the pattern design shown in Fig 1-9 Table 1-4: holes'pitch, space to wall and diameter of thermoset plastics Hole diameter mm 3~6 6~10 10~18|18-30 Holes pitch, space to wall /mm 3~4 4~5 5~7 Table 1-5: relations of hole's diameters and depths Molding types Hole depth Through hole Blind hole Horizontal hole 2.5d <1.5d Compression molding Vertical hole Extrusion or injection molding 4~5dExternal draft can be as small as ' 5 . Internal draft can be as small as ' ' 10 − 20 . A complex plastic part, which is difficult to eject, should adopt a larger draft. Usually a draft of ° ° 4 − 5 on each side is considered for a plastic part design with ribs or bosses. Larger draft should be chosen for a plastic product with large wall-thickness; during mold opening, in order that the product is retained on the side of the moving mold, draft of the inner surface should be smaller than that of the outer surface and the other way round, draft 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. Fig.1-8: draft Table 1-3: drafts for common plastic materials Draft Draft Plastic Types Core Cavity Plastic Types Core Cavity PE 20′~45′ 25′~45′ PMMA 35′~1° 35′~1°30′ PP&PVC-F 20′~50′ 50′~1° PA 20′~40′ 25′~40′ PVC-U 50′~1°45′ 50′~2° PC 30′~50′ 35′~1° PS 30′~1° 35′~1°30′ CPT 20′~45′ 25′~45′ ABS 35′~1° 40′~1°20′ POM 30′~1° 35′~1°30′ 1.2.6 Hole Design Holes may exist on a plastic part, including through holes, blind holes, screwed holes, and irregular shaped holes. In principle, holes should be as simple as possible. A complex hole increases the difficulty of mold making. As shown in Table 1-4, a sufficient gap should be reserved between holes or between a hole and the wall. The diameter of a hole also relates to its depth as shown in Table 1-5. When the distance between two holes or from the hole to the edge is smaller than the one specified in Table 1-4, please refer to the pattern design shown in Fig.1-9. Table 1-4: holes’ pitch, space to wall and diameter of thermoset plastics Hole diameter mm ＜1.5 1.5~3 3~6 6~10 10~18 18~30 Holes’ pitch, space to wall /mm 1~1.5 1.5~2 2~3 3~4 4~5 5~7 Table 1-5: relations of hole’s diameters and depths Molding types Hole depth Through hole Blind hole Horizontal hole 2.5d ＜1.5d Compression molding Vertical hole 5d ＜2.5d Extrusion or injection molding 10d 4~5d