Basic design principle of mold

Since different molding molds have been applied in many fields, and the manufacturing technology of professional molds has 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 mold includes batch size, molding equipment, precision conditions, geometric design, dimensional stability and surface quality.

1, batch size of the experiment, mold output hours, can be used for wood or resin manufacturing.However, if the experimental mold is to obtain the data of 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 production conditions.Molds are generally made of gypsum, copper, aluminum, or aluminum-steel alloys, and aluminum - resin is rarely used.

2, geometric design, design, often to consider the dimensional stability and surface quality.For example, the product design and dimensional stability require the use of female die (concave die), but the surface requirements of high gloss products require the use of male die (convex die), so that the plastic ordering party will take these two factors into account to enable the product to be produced under the best conditions.Experience has proved that the design which does not conform to the actual processing conditions is often a failure.

3, the size is stable, in the molding process, the plastic parts and the contact surface of the mold than leave the mold part of the dimensional stability is better.If the material thickness is changed due to the requirement of material stiffness in the future, the male die may be converted to female die.The dimensional tolerance of plastic parts shall not be less than 10% of the shrinkage.

4, the plastic surface, in terms of the scope of the molding material can be covered, the surface structure of the visible surface of the plastic parts should be formed in contact with the mold.If possible, the smooth surface of the plastic parts should not come into contact with the surface of the mold.Just like in the case of the bathtub and washtub made with the female mold.

5, modification, if the use of mechanical horizontal saw off the plastic clamping edge, in the direction of height, at least 6 ~ 8mm margin.Other finishing work, such as grinding, laser cutting or jet flow, must also leave a margin.The gap between the cutting lines of the cutting edge die is the smallest, 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 contract (such as PE), some plastic parts are easy to deformation, no matter how to prevent, plastic parts in the cooling phase will occur deformation.In this condition, we must change the shape of the mold to adapt to the geometric deviation of the plastic parts.For example, although the wall of the plastic parts remains flat, its reference center has deviated by 10mm;The mold base can be raised to adjust the shrinkage of this deformation.

7, shrinkage, in the manufacture of plastic molding mold must consider the following shrinkage factors.(1) shrinkage of molded products.If the shrinkage rate of the plastic is not clearly known, it must be obtained by sampling or by testing with a mould of similar shape.Note: this method can only get the shrinkage, not the deformation size.The adverse effect of the medium caused by shrinkage, such as ceramics, silicone rubber, etc.(3) the mold used to shrink the material, such as when casting aluminum shrinkage.