The design of the exhaust system
for large, deep cavity plastic parts to prevent vacuum during ejection and plastic deformation, need to set the suction device. Choose exhaust slot position is very important, generally in the plastic melt filling cavity at the same time, must put the gas out of the mould. Or high temperature air is compressed, cause local coking burning plastic parts, or bubble plastic, or reduce weld line strength caused by defects. Especially for precision, large mold, reasonable exhaust slot is more important.
the overall structure of the assembly drawing is used to express the mould, appearance size, structure and the mutual relation of each part is also used to guide the assembling, testing, installation and maintenance of technical documentation. Content is more, in the assembly drawing design, the design process is more complex, often to calculation, drawing, and modify until the final assembly drawing. Preliminary sketch drawing die structure design is the first stage of the mold assembly drawing, the basic content is according to the variety of plastic pieces used plastic, plastic pieces of size, complexity, high and low precision, batch size to determine the structure of the mould, that is single cavity or cavity, type is single parting surface or points. Selected cavity quantity, injection molding machine, and through calculating and selecting the determine the flow length and cross section size, you can begin to sketch map.
molding process, mold temperature will directly affect the plastic melt in the molding, finalize the design, molding cycle, and the quality of plastic parts. Mold temperature is too high, molding shrinkage, demoulding after plastic deformation is large, but also cause overflow of material and mold. Mold temperature is too low, the melt illiquid, molded parts outline is not clear, the surface will produce obvious defect such as silver, or flow lines. When the temperature of the mold is uneven, core and cavity temperature difference is too big, plastic pieces of uneven contraction, lead to plastic parts warp distortion, will affect the shape and dimension precision plastic parts.
the mold need to set the temperature control system in order to achieve the ideal temperature requirements. The design of temperature control system is a relatively tedious work, should not only consider the cooling effect and cooling uniformity, thermosetting plastic is heating effect and uniformity of heating, and to consider impact on the whole structure of the mold temperature control system. Thermoplastic film cooling system should be more detailed theoretical calculation. Generally divided into dynamic and fixed mode between the guidance, the push plate of the guidance, push a plate of orientation.
in the injection molding processing parts in trial production condition or bulk is small, or in the motor core pulling is complex, or cannot achieve, plastic pieces of the side parting and core pulling parts often USES the manual form. Manual classification is divided into a mould manual core-pulling and mold manually core-pulling two categories. Using core, inserts and push rod, fit clearance, takes advantage of the gap parting surface can be beneficial to exhaust, of course the exhaust slot is also can make full use of.
general guide due to restricted by the machining accuracy or use after a period of time, its precision is lower, will directly affect the precision of plastic parts, therefore the accuracy requirement high precision plastic parts must be design guide positioning device. When using standard mould base, because of the die set itself with guide, under normal circumstances, the designer as long as according to choose to die set specifications. If need with precision guide positioning device, it must be conducted by design personnel according to the mould structure design, such as using conical positioning positioning, cant for rectangular cavity adopt fine positioning, etc.
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