The design of vacuum blister forming mould includes batch size, forming equipment, precision condition, geometrical shape design, dimensional stability and surface quality.
1. Batch size experiment, die production hours, wood or resin can be used for manufacturing. However, if the experimental mold is to obtain the products about shrinkage, dimensional stability and cycle time, and so on, should use a single cavity mold to experiment, and to ensure that it can be used in production conditions. Mold is generally made of gypsum, copper, aluminum or aluminum-steel alloy, rarely used aluminum-resin.
2. Geometric shape design, design, often need to consider the size of stability and surface quality. For example, product design and dimensional stability require the use of yin Die (die), but the surface requirements of higher gloss products but require the use of master (convex die), so that the plastic parts order will be integrated into the two points, so that products can be under the best conditions for production. Experience has shown that designs that do not conform to actual processing conditions are often unsuccessful.
3. Dimensional stability, in the molding process, the plastic parts contact with the mold surface than to leave the mold part of the dimensional stability is better. If the material thickness is changed in the future due to the requirement of material stiffness, it may lead to the conversion of the Yang mode to the yin mode. The size tolerances of the plastic parts cannot be less than 10% of the shrinkage rate.
4, plastic parts surface, in terms of molding materials can be covered by the scope, plastic parts can meet the surface structure should be in contact with the mold molding. If possible, the smooth surface of the plastic parts do not contact with the mold surface. It's like using a mold to make a tub and a laundry tub.
5. Modification, if a mechanical horizontal saw is used to cut off the clamping edge of the plastic piece, at least there must be a 6~8mm margin in the height direction. Other finishing tasks, such as grinding, laser cutting or jet, must also be left over. Die cutting line between the smallest clearance, punching mold trimming when the distribution width is also very small, these are to be noted.
6. Shrinkage and deformation, plastic easy to shrink (such as PE), some plastic parts easily deformed, regardless of prevention, plastic parts in the cooling stage will occur deformation. Under this condition, it is necessary to change the shape of the molding mould to fit the geometrical deviation of the molded parts. For example: Although the molded wall remains straight, its datum center has deviated from 10mm, and the mold base can be elevated to adjust the shrinkage of the deformation.
7. Shrinkage, the following shrinkage factors must be taken into account in the manufacture of blister molding molds. ① Molded products shrink. If the shrinkage rate of plastic is not clearly known, it must be sampled or tested with similar shapes. Note: This method can only get the shrinkage rate, not the deformation size. ② the adverse effects of intermediate medium on shrinkage, such as ceramics, silicone rubber and so on. ③ the shrinkage of the material used in the mould, such as when casting aluminum.