Chapter 2 Mold design 2.1 Molding parts Molding parts refer to those in direct contact with plastics to form the shape of plastic parts, wherein those constituting the contour of the plastic parts are called cavities and those constituting the internal shape of the plastic parts are called cores. Since the cavity and core directly contact the plastics of high temperature and pressure and rub with the plastic parts when protruding, it is thus required that they are provided with sufficient intensity, rigidity, hardness, abrasion resistance corrosion resistance as well as low enough surface roughness 2.1.1 Structural design 1. Cavity Structural Design 1)Integral Cavity Directly cut cavity in the die set plate as indicated in Fig. 2-1. The advantage thereof is that the processing cost is relatively low. Yet the molding board material for making the die set is usually common medium carbon steel which is short in service life if used as cavity parts, whereas selecting materials with high performance shall result in high production cost. Usually, for the mold and precision of plastic parts which are less than 10000 times of molding, relatively low requirements are made; therefore, for molds of simple shape, integral structure can be adopted ig.2-1: integral ca 2) Integral Embedded Cavity Use high quality materials(high-carbon steel or alloy tool steel)which are slightly larger than the external shape of the plastic parts(wall thickness of sufficient intensity must be ensured)to make the cavity parts and embed them into the molding plate thereafter, as indicated in Fig. 2-2 The advantage is that the service life of the cavity parts can be ensured and meanwhile the material cost is reduced. Furthermore, it is easy and convenient to repair and replace the cavity parts if they are damagedChapter 2 Mold Design 2.1 Molding Parts Molding parts refer to those in direct contact with plastics to form the shape of plastic parts, wherein those constituting the contour of the plastic parts are called cavities and those constituting the internal shape of the plastic parts are called cores. Since the cavity and core directly contact the plastics of high temperature and pressure and rub with the plastic parts when protruding, it is thus required that they are provided with sufficient intensity, rigidity, hardness, abrasion resistance, corrosion resistance as well as low enough surface roughness. 2.1.1 Structural Design 1. Cavity Structural Design 1) Integral Cavity Directly cut cavity in the die set plate as indicated in Fig. 2-1. The advantage thereof is that the processing cost is relatively low. Yet the molding board material for making the die set is usually common medium carbon steel which is short in service life if used as cavity parts, whereas selecting materials with high performance shall result in high production cost. Usually, for the mold and precision of plastic parts which are less than 10000 times of molding, relatively low requirements are made; therefore, for molds of simple shape, integral structure can be adopted. Fig.2-1: integral cavity 2) Integral Embedded Cavity Use high quality materials (high-carbon steel or alloy tool steel) which are slightly larger than the external shape of the plastic parts (wall thickness of sufficient intensity must be ensured) to make the cavity parts and embed them into the molding plate thereafter, as indicated in Fig. 2-2. The advantage is that the service life of the cavity parts can be ensured and meanwhile the material cost is reduced. Furthermore, it is easy and convenient to repair and replace the cavity parts if they are damaged