Because different molding dies have been applied in many fields, and the manufacturing technology of professional dies has also undergone certain changes and developments in these years, in this part, the general design rules of vacuum blistering dies are summarized.
The design of vacuum forming molds includes batch size, molding equipment, precision conditions, geometric design, dimensional stability and surface quality.
1. The size of the batch is used for experiments. When the mold output is small, it can be made of wood or resin. However, if the experimental mold is used to obtain data on shrinkage, dimensional stability, and cycle time of the product, a single cavity mold should be used for the experiment and it can be used under production conditions. Molds are typically made of gypsum, copper, aluminum or aluminum-steel alloys, and aluminum-resins are rarely used.
2, Geometric shape design, design, often have to consider the dimensional stability and surface quality. For example, product design and dimensional stability require the use of a female mold, but the surface requires a higher gloss product, but requires the use of a male mold, so that the plastic parts ordering party will take these two points into consideration, so that the product can be the most Production under good conditions. Experience has shown that designs that do not meet actual processing conditions often fail.
3, The size is stable, in the molding process, the surface of the plastic part in contact with the mold is better than the dimensional stability of the part leaving the mold. If the material thickness is required to change in the future due to the material stiffness, it may result in the conversion of the male mold to the female mold. The dimensional tolerance of the plastic part cannot be less than 10% of the shrinkage rate.
4. The surface of the plastic part. In terms of the range in which the molding material can be wrapped, the surface structure of the visible surface of the plastic part should be formed at the contact with the mold. If possible, the clean side of the plastic part should not come into contact with the mold surface. It's like using a female mold to make a tub and a laundry tub.
5, Modification, if you use a mechanical horizontal saw to saw off the clamping edge of the plastic part, in the height direction, at least 6 ~ 8mm of the balance. Other finishing work, such as grinding, laser cutting or jetting, must also leave a margin. The gap between the cutting lines of the knife die is the smallest, and the distribution width when the punching die is trimmed is also small, which is to be noted.
6, Shrinkage and deformation, plastic shrinkage (such as PE), some plastic parts are easy to deform, no matter how to prevent, plastic parts will be deformed during the cooling phase. Under this condition, the shape of the forming mold is changed to accommodate the geometrical deviation of the plastic part. For example, although the wall of the plastic part is kept straight, the center of the reference has deviated by 10 mm; the base of the mold can be raised to adjust the amount of shrinkage of this deformation.
7. The amount of shrinkage must be considered in the manufacture of plastic forming molds. 1 The molded product shrinks. If the shrinkage of the plastic is not clearly known, it must be sampled or tested by a similarly shaped mold. Note: Only shrinkage can be obtained by this method, and the deformed size cannot be obtained. 2 The shrinkage caused by the adverse effects of the intermediate medium, such as ceramics, silicone rubber, etc. 3 Shrinkage of the material used in the mold, such as shrinkage when casting aluminum.