First, the design basis, dimensional accuracy and the correctness of its related dimensions.
According to the specific requirements and functions of the whole plastic product, which kind of appearance standard and specific size should be determined: plastic products with higher appearance quality requirements and lower dimensional accuracy requirements, such as toys; Functional plastic products, strict size requirements; Plastic products with strict appearance and size requirements, such as cameras. Whether the demoulding inclination of products is reasonable. Demoulding slope is directly related to the demoulding and quality of plastic products, i.e. whether the injection can proceed smoothly during the injection process: whether the demoulding slope is sufficient; The slope should be adapted to the plastic product's parting surface or parting surface. Whether it will affect the accuracy of appearance and wall thickness dimensions; Whether it will affect the strength of certain parts of plastic products.
Second, analysis and digestion of plastic product drawings and entities (samples) in the early stage of design.
A. geometric characteristics of products;
B. dimensions and tolerances
C. product technical requirements,
D, plastic particle category, brand,
E. product appearance requirements
F. inspection standards
Third, the number of cavities and cavity arrangement
A, injection machine maximum injection quantity is satisfied;
B, injection machine clamping force is satisfied;
C, mold shape size meets several requirements
D. product accuracy and color.
E, products with or without side axle core and its treatment method.
F. batch production of products.
G, economic benefits (production value per module)
H, evaluation of molding cycle
4. Determination of parting surface
A, try not to affect the appearance
B, fully ensure the product precision and facilitate subsequent mold machining.
C, the design of gating system, exhaust system and cooling system should be facilitated
D, it is necessary to facilitate mold opening (parting and demolding) to ensure that the product is left on one side of the movable mold during mold opening.
Fifth, the design of gating system
The design of gating system includes the selection of main runner, the determination of cross-sectional shape and size of shunt runner, the selection of gate location, the determination of gate form and cross-sectional size of gate. When using point gate, attention should also be paid to the design of de-gating device in order to ensure the shedding of shunt runner. When designing the gating system, the first thing is to select the location of the gate. The selection of gate location is directly related to the product molding quality and the smooth progress of the injection process. The selection of gate location should follow the following principles:
A, the gate position should be selected on the parting surface as far as possible, so as to facilitate the gate cleaning during mold processing and use;
B, the distance between the gate position and each part of the cavity should be consistent as far as possible, and the flow of the mold should be the shortest.
C, the location of the gate should ensure that when the plastic flows into the cavity, the free from worry and thick-walled parts in the cavity are aligned to facilitate the smooth flow of plastic;
D, the gate position should be opened at the thickest section of the plastic part;
E, avoiding the plastic from hitting the cavity wall, the core or the insert when flowing down the cavity, enabling the plastic to flow into each part of the cavity as soon as possible, and avoiding the deformation of the core or the insert;
F, try to avoid making the product produce weld marks, or making the weld marks produce in unimportant parts of the product;
G, the gate position and the plastic inflow direction shall be such that when the plastic flows into the mold cavity, it can flow evenly along the parallel direction of the mold cavity, and is conducive to the discharge of gas in the mold cavity;
H, the gate should be set at the part of the product that is easiest to remove, while not affecting the appearance of the product as much as possible.
VI. Design of Exhaust System
Exhaust system plays a vital role in ensuring the molding quality of products.
A, using the exhaust slot, the exhaust slot is generally located in the last filled part of the cavity, the depth of the exhaust slot varies with different plastics, and is basically determined by the maximum allowable clearance of plastic without flash, such as POM below 0.02.
B, use the fit clearance of core insert push rod or exhaust insert needle to exhaust.
C, in order to prevent the product from vacuum deformation during ejection, air blowing holes shall be set.
D, in order to prevent the vacuum adsorption between the product and the mold cavity, it is necessary to design an air cap.
VII. Design of Cooling System
The design of the cooling system is a rather complicated work, that is, the cooling effect and cooling uniformity should be considered, and the influence of the cooling system on the overall structure of the mold should also be considered.
A. arrangement of cooling systems and specific forms of cooling systems;
B, determining the specific position and size of the cooling system;
C, cooling of key parts such as moving dies or inserts; Cooling of slide block and inclined top;
D, design of cooling elements and selection of cooling standard elements;
E. rationality of overall seal structure design of cooling system.
