With the rapid development of economy, cosmetics and skin care products have gradually become daily consumer goods in life. In the competitive cosmetics consumption market, novel cosmetics packaging is one of the main reasons to attract consumers to buy and an important form to reflect the value of cosmetics. Even if there are a large number of advertisements, its packaging is also a persuasive promotion. When buying cosmetics, the first thing that attracts consumers' attention is the outer packaging, so the packaging design is very important.
Requirements for the surface of cream bottle: the outer surface is beautiful, the inner and outer wall surfaces are smooth after molding, and the surface roughness value is Ra0 1~0.2 μm. Visible black spots, gate marks, shrinkage marks, surface flow marks, welding marks, deformation, cracks, insufficient filling and other defects are not allowed. Functional requirements: the plastic part and the cover rotate smoothly, and the material in the container can be protected from pollution after assembly. The cream bottle is made of PETG. Its transparency allows consumers to see the contents of the container directly. It has excellent impact resistance and toughness, which ensures that it is not easy to be damaged during use. It also has strong acid and alkali resistance, but it has poor fluidity and high viscosity. The mold requires that the part surface of the molded plastic part is bright, the flow channel is smooth, and the exhaust design is reasonable. The plastic part is transparent, with a mass of 80g, a capacity of 115ml, a minimum wall thickness of 1.55mm and a maximum wall thickness of 5.9mm. Fillet transition is adopted at all connections to avoid stress concentration and cracks.
During injection molding, the mold temperature directly affects the melt filling and molding quality of plastic parts. A good cooling system will shorten the molding cycle and improve the production efficiency. Due to the thick wall of the molded plastic part, the hot runner system is used to adjust the mold temperature, and the cavity insert water path and fixed mold water path are designed into a parallel structure, as shown in Figure 7. According to the mold layout structure, two cavities are provided with one set of water paths, and there are four sets of water paths for the fixed mold insert and the fixed mold. As shown in Figure 8, the temperature in the cavity can be adjusted separately. Four separate groups of waterways are used in the dynamic model cavity. The core waterways of the dynamic model are shown in Figure 9. The cooling water enters from the top surface and flows out of the threaded mouth to enhance the cooling effect.
During the molding process, the air in the mold must be discharged. PETG material has poor fluidity and large shear force in the screw. Reasonable exhaust design can avoid flow marks and welding marks of molded plastic parts caused by trapped gas, reduce the injection pressure, shorten the injection time, pressure holding time and molding cycle, eliminate the internal stress of plastic parts, and prevent deformation and warpage. Exhaust grooves are set on the parting surface of the cavity, fixed mold inserts and moving mold core.
Post time: Apr-22-2022