A hole in the workpiece, there is a core pin'in the mold correspondingly. Core pin Is commonly referred to as core pin shift. A general rule, holes design is that a wall located near a hole should be a minimum of one hole diameter away to obtain maximum workpiece strength and facilitate melt flow.
In a plastic workpiece, a through hole is preferred to a"blind hole". A through hole, core pins that are used to form the holes are supported by both mold halves and can withstand the high injection pressures of the plastic melt. Blind holes, means to use an unsupported core pin, which may bend or deflect when the ratio of length to radius is over 2, because it expose to the high injection pressures of the plastic melt.
Holes in plastic workpieces may be molded perpendicular to movement of the mold, parallel movement of the mold, and at oblique angles. The orientation of hole will affect the structure of mold.A hole in workpiece or the forming core pin parallel to the draw as it opens and closes, the draw will simplify the mold. Holes may also be molded at right angles and at oblique angles tha need an watercut insert system to form. Fig. 2. 19 shows different orientation of holes. If it is possible that the oblique-angle holes should be avoided, because the mold cost will increase greatly compare with the mold with the core pin that parallel to the draw. Right angles are not recommended in general design, because they require split molds. and retractable core pins.
