The design of vacuum forming mould includes batch size, forming equipment, precision condition, geometry design, dimensional stability and surface quality.
1, the size of the experimental batch, mold output hours, can be used for manufacturing wood or resin. However, if the experimental die is used to obtain data on shrinkage, dimensional stability and cycle time of the product, the single-cavity die should be used to test and ensure that it can be used in production conditions. Molds are usually made of gypsum, copper, aluminum, or aluminum-steel alloys, rarely using aluminum-resin.
2, geometric shape design, design, often comprehensive consideration of dimensional stability and surface quality. For example, the design and dimensional stability of the product requires the use of a female mold (die), but the surface of the product requires a higher degree of gloss requires the use of a male mold (punch), so that the plastic parts order will take into account these two points, so that the product can be produced under the best conditions. Experience has proved that the design which does not meet the actual processing conditions is often a failure.
3, dimensional stability, in the molding process, plastic parts and mold contact surface than leave the mold part dimensional stability. If the material thickness needs to be changed in the future due to the material stiffness, it may be necessary to convert the male model to the female model. The dimensional tolerance of plastic parts should not be less than 10% of shrinkage.
4. The surface of plastic parts. As far as the molding material can be covered, the surface structure of the visible surface of plastic parts shall be formed at the contact with the mold. If possible, the smooth surface of the molded part should not be in contact with the surface of the mold. As in the case of the bath and washing tub, the mould is used.
5, modification, if the use of mechanical horizontal saw off the clamping edge of plastic parts, in the height direction, at least 6 ~ 8mm margin. Other finishing jobs, such as grinding, laser cutting or jet cutting, must also be left with margin. The clearance between cutting lines of cutting edge die is the smallest, and the distribution width of punching die dressing is also small, which should be paid attention to.
6, shrinkage and deformation, plastic easy shrinkage (such as PE), some plastic parts easy deformation, no matter how to prevent, plastic parts 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 plastic parts. For example, although the wall of the piece remains straight, its reference center has been deviated by 10mm; The die base can be raised to adjust the shrinkage of this deformation.
7, shrinkage, in the manufacture of blister 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 sampling or testing with molds of similar shapes. Note: this method can only get shrinkage, not deformation size. (2) the adverse impact of the medium caused by shrinkage, such as ceramic, silicone rubber, etc. (3) the shrinkage of the material used in the mold, such as the shrinkage of casting aluminum.