Because different molding molds have been applied in many fields, and the manufacturing technology of professional molds has also changed and developed in recent years, the general design rules of vacuum Blister molding molds are summarized in this part.
The design of vacuum blister forming die includes batch size, forming equipment, precision conditions, geometric shape design, dimensional stability and surface quality.
1、For large and small experiments in batches, the mold output is small, and can be made of wood or resin. However, if the experimental mold is used to obtain the data about shrinkage, dimensional stability and cycle time of the product, the single cavity mold should be used for the experiment, and it can be guaranteed to be used under production conditions. The mold is usually made of gypsum, copper, aluminum or aluminum steel alloy, and aluminum resin is rarely used.
2、In geometric design, dimensional stability and surface quality are often considered comprehensively. For example, product design and dimensional stability require the use of female molds (female molds), but products with high surface gloss require the use of male molds (male molds). In this way, the ordering party of plastic parts will comprehensively consider these two points, so that the products can be produced under the best conditions. Experience has proved that the design that does not meet the actual processing conditions is often a failure.
3 、Dimensional stability: during the molding process, the surface of the plastic part in contact with the mold has better dimensional stability than the part away from the mold. If the material thickness is required to be changed due to the need of material rigidity in the future, it may lead to the conversion of male mold to female mold. The dimensional tolerance of plastic parts shall not be less than 10% of shrinkage.
4 、For the surface of the plastic part, the surface structure of the plastic part that can be covered by the molding material should be formed at the contact with the mold. If possible, the clean surface of the plastic part should not contact the mold surface. Just like the case of making bathtubs and washing tubs with negative molds.
5、If the clamping edge of the plastic part is sawed off with a mechanical horizontal saw, there should be at least 6-8mm allowance in the height direction. Other finishing work, such as grinding, laser cutting or jet, must also have allowance. The gap between the cutting edges and the cutting lines is the smallest, and the distribution width of the punching die during trimming is also very small, which should be paid attention to.
6 、Shrinkage and deformation: plastic is easy to shrink (such as PE), and some plastic parts are easy to deform. No matter how to prevent, plastic parts will deform in the cooling stage. Under this condition, the shape of the molding die must be changed to adapt to the geometric deviation of the plastic part. For example, although the plastic part wall remains straight, its reference center has deviated by 10mm; The mold base can be raised to adjust the shrinkage of this deformation.
7、Shrinkage: the following shrinkage factors must be considered when manufacturing the Blister molding mold. ① The molded product shrinks. If the shrinkage of plastic can not be clearly known, it must be obtained by sampling or testing with a mold of similar shape. Note: only the shrinkage can be obtained by this method, and the deformation size cannot be obtained. ② Shrinkage caused by adverse effects of intermediate media, such as ceramics, silicone rubber, etc. ③ Shrinkage of materials used in molds, such as aluminum casting.