Time： 2019-03-12 15:47:08
Since different moulds have been used in many fields, and the manufacturing technology of professional moulds has changed and developed in recent years, the general design rules of vacuum forming moulds are summarized in this part.
The design of vacuum forming mold includes batch size, forming equipment, precision condition, geometry design, dimensional stability and surface quality, etc.
1, the size of the batch of experimental, mold output is small, can use wood or resin for manufacturing. However, if the test mold is used to obtain the data of shrinkage, dimensional stability and cycle time of the product, the single-cavity mold should be used to test, and ensure that it can be used in production conditions. Moulds are generally made of gypsum, copper, aluminum or aluminum - steel alloys, with little use of aluminum - resin.
2. In the design of geometric shapes, dimensional stability and surface quality should always be taken into consideration. For example, the design and dimensional stability of the product requires the use of a negative mold (concave mold), but the surface requires a high gloss products require the use of a positive mold (punch), so that the plastic parts ordering side will take these two factors into account, so that the products can be produced under the best conditions. Experience has proved that the design which does not conform to the actual processing conditions is often a failure.
3, dimensional stability, in the molding process, the plastic parts and the mold contact surface than leave the mold part of the dimensional stability is better. If the thickness of the material needs to be changed due to the stiffness of the material in the future, it may lead to the conversion of the positive mold to the negative mold. The dimensional tolerance of plastic parts shall not be less than 10% of the shrinkage rate.
4, plastic parts surface, as far as the molding materials can cover the scope, plastic parts visible surface structure should be in contact with the mold molding. If possible, do not touch the surface of the mold with a clear surface. As in the case of the bath tub and washtub, which are molded in a negative mold.
5, modification, if the use of mechanical horizontal saw saw off the plastic parts of the clamping edge, in the direction of height, at least 6 ~ 8mm allowance. Other finishing work, such as grinding, laser cutting, or jet, must also have a margin. The gap between the edge of the die cutting line is the smallest, punching die dressing distribution width is also very small, these are to pay attention to.
6, shrinkage and deformation, plastic easy shrinkage (such as PE), some plastic easy deformation, no matter how to prevent, plastic in the cooling phase will occur deformation. In this condition, it is necessary to change the shape of the molding mold to adapt to the geometric deviation of the plastic parts. For example, although the plastic wall remains flat, its reference center has deviated from 10mm; The mould base can be raised to adjust the amount of shrinkage of this deformation.
7, shrinkage, in the manufacture of plastic molding mold must take into account the following shrinkage factors. (1) molding products shrinkage. If the shrinkage rate of the plastic is not clearly known, it must be obtained by testing with a sample or with a mould of similar shape. Note: this method can only obtain shrinkage, not deformation size. The adverse effect of the intermediate caused by shrinkage, such as ceramics, silicone rubber, etc. (3) mold used in the shrinkage of materials, such as casting aluminum shrinkage.
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