Design principle of mold

Update:11-01-2020
Summary:

Because different molding dies have been applied in man […]

Because different molding dies have been applied in many fields, coupled with the development of professional mold manufacturing technology in these years, there have been certain changes and developments. Therefore, in this section, the general design rules of vacuum suction molding dies are summarized.
The design of the vacuum plastic molding mold includes batch size, molding equipment, precision conditions, geometric shape design, dimensional stability and surface quality.
1. For batch size experiments, the mold output is small, and it can be made of wood or resin. However, if the experimental mold is to obtain data about shrinkage, dimensional stability, and cycle time of the product, a single cavity mold should be used for the experiment, and it can be guaranteed to be used under production conditions. Molds are generally made of gypsum, copper, aluminum, or aluminum-steel alloys, and aluminum-resin is rarely used.
2. Geometric shape design. When designing, often consider the dimensional stability and surface quality. For example, product design and dimensional stability require the use of female molds (concave molds), but products with higher surface gloss require the use of male molds (convex molds). In this way, the plastic purchaser will consider both Point so that the product can be produced under optimal conditions. Experience has proven that designs that do not meet actual processing conditions often fail.
3. Dimensional stability. During the molding process, the contact surface of the plastic part with the mold is better than the dimensional stability of the part leaving the mold. If the thickness of the material is required to be changed in the future due to the rigidity of the material, the male mold may be converted into a female mold. The dimensional tolerance of plastic parts must not be less than 10% of the shrinkage.
4. The surface of the plastic part, as far as the molding material can cover, the surface structure of the visible surface of the plastic part should be formed at the point of contact with the mold. If possible, do not touch the smooth surface of the plastic part with the mold surface. It's like the case of making bathtubs and laundry tubs with negative molds.
5. Modification. If a mechanical horizontal saw is used to saw off the clamping edge of the plastic part, there must be at least 6 to 8 mm margin in the height direction. Other dressing work, such as grinding, laser cutting, or jetting, must also allow margin. The gap between the cutting edges of the cutting edge die is the smallest, and the distribution width of the punching die when trimming is also small. These should be paid attention to.
6, shrinkage and deformation, plastic is easy to shrink (such as PE), some plastic parts are easy to deform, no matter how to prevent, plastic parts will deform during the cooling stage. Under this condition, it is necessary to change the shape of the forming mold to adapt to the geometric deviation of the plastic part. For example: Although the wall of the plastic part is kept 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 taken into account when manufacturing blister molding molds. ① The molded product shrinks. If the shrinkage of the plastic cannot be clearly known, it must be sampled or obtained by testing with a similarly shaped mold. Note: Only shrinkage can be obtained by this method, and deformation size cannot be obtained. ② Shrinkage caused by the adverse effects of intermediate media, such as ceramics, silicone rubber, etc. ③ Shrinkage of materials used in the mold, such as shrinkage when casting aluminum.