Design principle of die

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 design, dimensional stability and surface quality.

1. The size of the batch is used for experiments, and the output of the mold is hours. It 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 used under the production conditions. Molds are generally made of gypsum, copper, aluminum or aluminum steel alloy, and aluminum resin is rarely used.

2. In geometric design, dimensional stability and surface quality should be considered comprehensively. For example, the product design and dimensional stability require the use of female mold (female mold), but the products with high surface gloss require the use of male mold (male mold). In this way, the plastic parts ordering party will comprehensively consider these two points, so that the products can be produced under good conditions. Experience has proved that the design that does not meet the actual processing conditions often fails.

3. Dimensional stability. In the molding process, the dimensional stability of the contact surface between the plastic part and the mold is better than that of the part leaving the mold. If the material thickness is required to be changed due to the need of material stiffness 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 plastic parts, the visible surface structure of plastic parts shall be formed at the contact with the mold in terms of the range that can be covered by the forming material. If possible, the polished surface of the plastic part shall not contact with the mold surface. It's like making bathtubs and washing basins with female molds.

5. For decoration, if the clamping edge of plastic parts is sawed off by mechanical horizontal saw, there shall be at least 6 ~ 8mm allowance in the height direction. Allowance must also be made for other finishing work, such as grinding, laser cutting or jet. The gap between the cutting lines of the knife edge die is small, and the distribution width of the punching die 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, it is necessary to change the shape of the forming die to adapt to the geometric deviation of the plastic part. For example: Although the plastic part wall remains straight, its datum center has deviated by 10mm; The die base can be raised to adjust the shrinkage of this deformation.

7. Shrinkage, the following shrinkage factors must be considered when manufacturing blister forming molds. ① Shrinkage of molded products. If the shrinkage rate of plastic cannot 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 the material used in the mold, such as when casting aluminum.