In the whole process of high gloss and non trace injection molding, the quality of mold design is one of the important factors that directly affect the quality of products. The quality of mold also directly leads to the key of product appearance quality and product cycle
The main factors affecting molds include mold materials, mold design, manufacturing, and processing.
(1) Mold materials Mold materials need to have good polishing, corrosion resistance, wear resistance, thermal strength, toughness, processing performance, and low thermal expansion coefficient. Polishing, corrosion resistance, thermal strength, and coefficient of thermal expansion are particularly important for high-gloss molds. If the mold has poor polishing performance, large surface roughness, or is corroded or there is water deposition during injection molding, it cannot be used for high gloss product molding; The rapid changes in temperature also have higher requirements for the thermal strength and thermal expansion coefficient of mold materials. Currently, the high gloss mold materials used include Hitachi Metal CENA1, Japan's Datong NAK80 and S-STAR, ASSAB's 5136 or S136H (420), POLMAX, and other mirror faced, high wear resistant, and corrosion resistant mold materials. Low grade high gloss molds also use conventional mold materials such as P20. CENAL, a material for super large plastic molding molds developed by Hitachi Metal α It is a product specially developed for high-gloss molds and won the 2007 Japan New Product Award. Its comprehensive performance is good, with good wear resistance, processability, toughness, and corrosion resistance, while its polishing performance is excellent. It is one of the best mold materials for high-gloss mirror surface molding.
(2) Mold Design and Manufacturing High gloss molds require high surface quality. In addition, the dynamic changes in mold temperature lead to a much more complex structure than ordinary molds. The design and manufacturing of the internal pipes of the mold is the key to affecting mold quality, production cycle, and mold cost.
In order to ensure the uniformity and rapid change of mold surface temperature, reasonable pipes must be set up inside the mold to ensure rapid heating and cooling. The pipe system of conventional molds generally adopts linear pipes and is realized through drilling. This design and manufacturing is only suitable for products with relatively simple surface structures, such as DVD panels, LCD surface shells, and other household appliance shells, but it cannot meet the mold surface temperature uniformity requirements of complex molds. Complex high-gloss molds meet the above requirements by arranging pipes at a constant distance from the mold surface through a layered structure or other special methods, wherein the layered structure is relatively easy to achieve. The layered cavity and/or core hill are composed of two parts: the upper layer is a cavity part with a basically uniform thickness, and the front surface is processed to form a mold molding surface, the back surface is processed to form a uniform spatial semicircular pipe, and the lower layer is a liner plate, which has a matching surface corresponding to the upper layer of parts, and also processes a uniform spatial semicircular pipe. The upper and lower layers cooperate to form a spatial pipe to solve the uniformity of heat conduction, The surface temperature of the mold can be uniformly raised in a short time. Compared to ordinary molds, due to the large number of pipes and their proximity to the mold surface, the cooling and heating times can be greatly shortened, resulting in shorter high-gloss injection molding cycles than conventional injection molding cycles, achieving rapid cyclic molding. However, the layered structure also leads to higher processing costs and shorter mold life.
In addition, the rapid cooling and heating cycle also puts forward higher requirements for other parts of the mold. In order to prevent the heating system from affecting other parts of the mold, careful consideration should be given to the heat insulation, sealing, and fitting of the moving mating parts of the positioning device, core pulling, and guide mechanism to avoid poor mold opening and closing, inability of the slider to move, and poor positioning.
In terms of high-gloss molds, there are currently problems such as single mold materials, high prices, high mold manufacturing costs, low mold life, complex mold manufacturing difficulties, and long cycle times, which limit high-gloss injection molding to products with simple structures, such as flat plastic shells and other external products with simple structures. In the future, it is necessary to research and develop new high-gloss precision mold manufacturing technologies and new mold materials, combining modern CAE technology, rapid manufacturing technology, polishing technology, surface processing technology, etc., to achieve efficient and precise design and processing of mold surfaces, mold internal pipes, and mold parts.