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Principle of mould design
Nov 20, 2017

Because different molding molds have been applied in many fields, coupled with the professional mold manufacturing technology in these years also has a certain change in development, so in this part, summed up the vacuum blister molding mold general design rules.

The design of vacuum blister forming mould includes batch size, forming equipment, precision condition, geometrical shape design, dimensional stability and surface quality.

1, the size of the experiment, the mold 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, the size is stable, in the molding process, the plastic parts and mold contact surface than leaving 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, the modification, if the use of mechanical horizontal saw cutting off the clamping edge of the plastic parts, in the height of the direction, at least have 6~8mm allowance. 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, in the manufacture of blister molding mold must take into account the following shrinkage factors. 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.

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