Because different molding moulds have been applied in many fields, and the manufacturing technology of professional moulds has also changed and developed in these years, so in this part, the general design rules of vacuum blister molding moulds are summarized.
The design of vacuum blister forming mold includes batch size, forming equipment, precision conditions, geometric design, dimensional stability and surface quality.
1, the size of the batch experiment, mold output hours, can be made of wood or resin. However, when experimental molds are used to obtain data on shrinkage, dimensional stability, and cycle time of the product, single-cavity molds should be used to ensure that they can be used in production conditions. Molds are generally made of gypsum, copper, aluminum, or aluminum-steel alloys, and aluminum-resin is rarely used.
2, geometric design, design, often to consider the dimensional stability and surface quality. For example, product design and dimensional stability requires the use of negative mold, but the surface requirements of higher gloss products are required to use male mold, so that plastic parts ordering party will take these two points into consideration, in order to make products can be produced under the best conditions. Experience has proved that the design which does not accord with the actual machining conditions is often a failure.
3, dimensional stability, in the process of forming, plastic parts and mold contact surface than leaving the mold part of dimensional stability is better. If the thickness of the material is changed later due to the stiffness of the material, it may be necessary to convert the male mode to the female mode. The dimensional tolerance of plastic parts shall not be less than 10% of shrinkage.
4, plastic surface, in terms of the scope of forming materials can be covered, plastic visible surface structure should be in contact with the mold molding. If possible, the smooth surface of the plastic part should not come into contact with the surface of the mold. As in the case of bidet and washtub.
5, modification, if the use of mechanical horizontal saw saw off the clamping edge of the plastic parts, in the height direction, at least 6 ~ 8mm allowance. Other finishing work, such as grinding, laser cutting or jet, must also have a margin. The gap between the cutting lines of the cutting die is minimal, and the distribution width of the punching die dressing is also very small, which should be noted.
6, shrinkage and deformation, plastic easy to shrink (such as PE), some plastic parts easy to deformation, no matter how to prevent, plastic parts will be deformed in the cooling stage. In this condition, it is necessary to change the shape of the mold to adapt to the geometric deviation of plastic parts. For example: although the plastic wall remains flat, but its reference center has deviated from 10mm; The mold base can be raised to adjust the amount of shrinkage for this deformation.
7, shrinkage, when manufacturing blister forming mold must take into account the following shrinkage factors. (1) Shrinkage of molding products. If the shrinkage of the plastic is not clearly known, it must be obtained by sampling or by testing with a similar shape mold. Note: only shrinkage can be obtained by this method, not deformation size. ② Shrinkage caused by adverse effects of intermediate media, such as ceramics, silicone rubber, etc. The shrinkage of the material used in the mold, such as the shrinkage of casting aluminum.