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Some plastic zipper bags are formed with a blind hole and then drilled. This method is suitable for thin and deep holes to prevent core deformation during molding. After the plastic product is formed, there is no hole, and the hole is processed twice afterwards. The latter two methods are limited to a few materials that are easy to cut, such as nylon. At the same time because of the secondary processing. The production efficiency is low, and the quality of the fine pores is difficult to guarantee, so it is used very little. This section mainly introduces the design principle and processing method of the hole directly formed during the forming of the ziplock bag.
The hole directly formed during molding, regardless of the type of service, should be placed at a portion that does not weaken the strength of the product, and the shape of the hole should not be complicated to complicate the mold manufacturing process. It is an important factor in the residual weld line of the molded product and the weakening strength. There is a convex edge around it to strengthen. At the same time, the distance between the holes and the holes and the distance from the edge of the product are also appropriate. The dimensional relationship shown determines that when the two holes are not the same size, the value is 7L; the injection molded article of the thermoplastic zipper bag is taken as 75% of the value in Table 2-7. For the depth of the hole, the difference is different. The depth of the type of hole varies depending on the molding method. The through hole injection molding product L is used in a large number of ways, and the core for forming the through hole generally has a door L type mounting method.
The core with a fixed inner end is formed, and the flash edge is easily generated, and the core is easy to bend when it is thin. This method of fixing the core cannot form deep holes. It is formed by two cores fixed at both ends, because one core is designed to be larger than the other. 5-1mm or so, to ensure the concentricity of the hole, does not cause difficulties in the installation and use of soil, but also increases the stability of the core, the hole accuracy is low. It is formed by a core fixed at one end and guided at one end, so that the core has better strength and rigidity, and can ensure concentricity, but the guiding portion is easy to cause arc flash due to wear of the guiding error. Regardless of the fixing method used above, the depth of the hole should not be too large, and the male core will bend. Usually, the fluidity of the plastic is 4 (the same, the plasticity of the self-sealing bag of 7L can reach 10 times the hole diameter, the medium mobility can not exceed 7 times the hole diameter, and the hole depth of the plastic product with poor fluidity. It is better to be less than 4 times 7L diameter; otherwise it can only be obtained by mechanical force method.
