Main Molding Process Classification and Matching Application Scenarios of China's Injection Molds
The manufacturing of industrial components, daily consumer goods, electronic consumables and medical devices relies on various molding mold technologies. Each molding method differs greatly in forming principles, mold structure costs, finished product precision and production capacity range. Proper matching between mold types and product requirements can balance production costs, delivery cycles and finished product quality. This paper sorts out six mainstream industrial molding technologies including injection molding, die casting, blow molding, rotational molding, stamping and silicone vulcanization based on the manufacturing reality of China's injection mold industry, clarifies their applicable products, working conditions and applicable limits, and provides standardized selection reference for domestic mold design and production enterprises.
I. Injection Molding Molds and Matching Application Scenarios
Injection molding molds melt plastic particles at high temperature and inject the molten material into closed cavities under high pressure for cooling and shaping, which is the most widely used molding process in China's plastic mold industry. The molds can be designed with multi-cavity structures, complex undercuts and thin-wall precision structures, featuring stable mass production performance. Applicable raw materials cover general and engineering plastics such as PP, ABS, PC and PA66, and precision small parts can reach dimensional tolerance of 0.01mm. Its matching application scenarios are divided into four categories: high-gloss mirror injection molds made of S136 and NAK80 steel are selected for consumer electronic shells, connectors and mobile phone structural parts; large mold base multi-cavity injection molds are applied to household appliance shells, washing machine accessories and air conditioner casings; food-grade compliant injection molds are used for food containers, tableware and infant supplies; two-color and overmolding large injection molds are adopted for automotive interior door panels, instrument housings and bumpers. This process is not suitable for ultra-large hollow thick-wall products and products with ultra-low single-piece output, as the mold opening cost cannot be shared efficiently for small-batch orders.
II. Die Casting Molds and Matching Application Scenarios
Die casting molds are used for high-pressure forming of molten lightweight metals such as aluminum alloy, zinc alloy and magnesium alloy. Domestic die casting molds are designed with high temperature and pressure resistance, and molded metal parts have high strength and smooth surfaces that can be directly electroplated without secondary polishing. Zinc alloy die casting molds are matched with small decorative hardware, electronic shielding covers, luggage locks and precision gear small parts; aluminum alloy die casting molds are widely used in auto engine shells, new energy battery casings, heat dissipation brackets and motor end covers; magnesium alloy die casting is mainly applied to lightweight 3C product shells and notebook frames. This technology fits mass production of small and medium-sized metal shells with wall thickness ranging from 1mm to 5mm, and integrated forming of complex hollow structures and reinforcing ribs can be realized. The limitation lies in the difficulty of manufacturing thick-wall castings, internal air hole defects, and inadaptability to pressure-sealed metal parts.
III. Blow Molding Molds and Matching Application Scenarios
Blow molding molds are split into hollow blow molding and injection stretch blow molding. High-pressure gas inflates plastic parisons to fit the inner wall of molds to form closed hollow products, with simpler structure and lower manufacturing cost compared with injection molds. Hollow blow molding is matched with chemical plastic barrels, engine oil bottles, beverage barrels, large water tanks and outdoor storage boxes produced by Chinese mold factories; injection stretch blow molding molds are specially used for transparent PET mineral water bottles, cosmetic bottles and medical oral liquid bottles, featuring high transparency and uniform wall thickness of finished products. Large rotational blow molding molds are applied to traffic anti-collision barrels and floating pontoons. This process only produces hollow parts, and cannot form precision undercut and complex assembly structural components. The dimensional accuracy of finished products is relatively low, so it is not applicable to precision assembly components.
IV. Rotational Molding Molds and Matching Application Scenarios
Rotational molding molds adopt low-temperature plastic powder raw materials. The molds rotate on two axes while heating to make powder evenly attach to the inner wall for cooling and forming. The molds bear extremely low pressure, so integrated seamless ultra-large hollow parts can be manufactured. Domestic rotational molding molds have low production cost and flexible modification space. They are mainly matched with large thick-wall containers such as sewage treatment tanks, chemical storage barrels, amusement plastic slides, road isolation piers and RV water tanks, and take priority for special-shaped hollow large parts and single-piece small-batch customized products. Its disadvantages include long molding cycle, low production capacity, rough surface of finished products, and incapability of producing thin-wall precision appearance parts.
V. Stamping Molds and Matching Application Scenarios
Stamping molds rely on presses to complete cold stamping, bending, stretching and cutting of metal sheets in one step, including single-operation molds, progressive stamping molds and drawing molds, featuring fast production speed and ultra-low single-piece cost. Progressive stamping molds are widely used by domestic hardware manufacturers for electronic shrapnels, terminals, small metal heat sinks and precision thin hardware; drawing stamping molds match stainless steel cup shells, kitchen basin bodies and auto oil tank shells; large stamping molds are applied to auto body panels, household appliance metal shells and distribution cabinet steel frames. The process is only applicable to metal sheet processing, unable to form plastic parts and three-dimensional structures with variable wall thickness. The precision of bending and punching depends entirely on the cutting edge and positioning structure of stamping molds.
VI. Silicone Vulcanization Molds and Matching Application Scenarios
Silicone vulcanization molds are divided into solid hot-press vulcanization molds and liquid silicone LSR injection molds, with accurate mold temperature control. Finished silicone products have excellent high and low temperature resistance, environmental friendliness and elasticity. Solid silicone molds are matched with ordinary sealing rings, anti-slip silicone mats and kitchen heat insulation handles; liquid LSR injection molds are adopted for medical silicone catheters, baby nipples, food sealing parts and mobile phone waterproof sealing rings, featuring high precision and no flash, and can realize integrated two-color molding with plastic materials. This technology is suitable for elastic products requiring flexibility, sealing performance and food medical safety certification, but not applicable to rigid structural parts. The unit price of raw materials and mold processing cost are higher than ordinary plastic injection molds.
Conclusion
All molding technologies supported by China's injection mold industry have clear applicable scene boundaries. Precision small plastic assembly parts and mass-produced appearance products give priority to injection molding molds; lightweight metal shells and hardware decorative parts select die casting molds; hollow bottles and sealed containers are matched with blow molding molds; ultra-large hollow thick-wall and small-batch anti-corrosion large parts adopt rotational molding molds; mass processing of metal sheets uses progressive stamping molds; food and medical elastic sealing parts fit silicone vulcanization molds. Mold selection needs to comprehensively consider five dimensions including product material, size, precision requirement, production volume and budget cost. Mismatched molding technology will lead to low qualified rate, excessive production cost and extended delivery cycle. Reasonable mold type selection can maximize the process advantages of various molding technologies, reduce unnecessary production loss, and improve the overall manufacturing efficiency of China's injection mold and plastic product industry.
