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What are the key elements of the vertical injection molding process?

by:FUHONG     2021-06-13
1. Vertical injection molding machine injection process. Crystalline thermoplastics can be divided into two categories: crystalline plastics and non-crystalline (also called amorphous) plastics according to their absence of crystallization during condensation. The appearance criteria for judging these two types of plastics depends on the transparency of the thick-walled plastic parts. Generally, crystalline materials are opaque or translucent (such as POM, etc.), and amorphous materials are transparent (such as PMMA, etc.). There are exceptions. For example, poly(4) methylpentene is a crystalline plastic but has high transparency, and ABS is an amorphous material but not transparent. When designing a mold and choosing a vertical injection molding machine, pay attention to the following requirements and precautions for crystalline plastics: ①. The material temperature rises to the molding temperature requires a lot of heat, and a vertical injection molding machine with a large plasticizing ability should be used. ②. A large amount of heat is released during cooling and reprocessing, so it must be cooled sufficiently. ③. The specific gravity difference between the molten state and the solid state is large, the molding shrinkage is large, and shrinkage and pores are prone to occur. ④. Fast cooling, low crystallinity, small shrinkage and high transparency. The crystallinity is related to the wall thickness of the plastic part, and the wall thickness is slow to cool, the crystallinity is high, the shrinkage is large, and the physical properties are good. Therefore, the crystalline material should be controlled according to the requirements of the vertical injection molding machine mold temperature. ⑤. Significant anisotropy and large internal stress. Molecules that have not crystallized after demolding have a tendency to continue to crystallize, are in an energy imbalanced state, and are prone to deformation and warpage. ⑥. The crystallization temperature range is narrow, and it is easy to cause unmelted material to be injected into the mold or to block the feed port. 2. Vertical injection molding machine injection process for heat-sensitive plastics and easily hydrolyzed plastics. Heat sensitivity refers to the tendency of certain plastics to be sensitive to heat, heating for a long time at high temperature or too small cross-section of the feed opening, when the shearing effect is large, the material temperature increases and the tendency of discoloration, degradation and decomposition occurs easily. Those with this characteristic Plastic is called heat-sensitive plastic. Such as hard PVC, polyvinylidene chloride, vinyl acetate copolymer, POM, polychlorotrifluoroethylene, etc. Heat-sensitive plastics produce monomers, gases, solids and other by-products during decomposition. In particular, some decomposition gases have irritation, corrosion or toxicity to the human body, equipment, and molds. Therefore, attention should be paid to mold design, selection of vertical injection molding machine, and molding. Screw injection molding machine should be used. The section of the pouring system should be large. The mold and barrel should be chrome plated. There should be no protrusions. The vertical injection molding must be strictly controlled. The molding temperature of the machine and the addition of stabilizers to the plastic weaken its heat-sensitive performance. 3. Stress cracking and melt fracture of the injection molding process of the vertical injection molding machine. Some plastics are sensitive to stress, and are prone to internal stress during molding and are brittle and easy to crack. Plastic parts crack under the action of external force or under the action of solvents. And should choose a reasonable shape of plastic parts, it is not appropriate to install inserts and other measures to minimize stress concentration. Recommended reading: (1) Rotary table injection molding machine, rotary table vertical injection molding machine, JTT-850R rotary table vertical injection molding machine brand manufacturers. (2) Turntable injection molding machine, turntable injection molding machine brand, well-known turntable injection molding machine manufacturer. (3) Vertical injection molding machine, standard vertical injection molding machine, disc injection molding machine, disc vertical injection molding machine, low pressure injection molding machine.
An increasing dependence on the use of automatic injection moulding machine micro injection molding has made numerous changes in the plastic blow moulding machine industry over the past decades.
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