The principle of mold design?

Update:07-12-2020
Summary:

Because different molding molds have been applied in ma […]

Because different molding molds have been applied in many fields, and the manufacturing technology of professional molds has also undergone certain changes and development in these years, this section summarizes the general design rules of vacuum forming molds.
The design of vacuum blister 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 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. The mold is generally made of plaster, copper, aluminum, or aluminum-steel alloy, and aluminum-resin is rarely used.
2. Geometric shape design. When designing, it is often necessary to comprehensively consider 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 (punch molds). In this way, the plastic parts ordering party will consider these two Point so that the product can be produced under the best conditions. Experience has proved that designs that do not meet the actual processing conditions often fail.
3. Dimensional stability. During the molding process, the surface of the plastic part in contact with the mold has better dimensional stability than the part leaving the mold. If the material thickness needs to be changed in the future due to the need of material rigidity, it may cause the male mold to be converted to the female mold. The dimensional tolerance of plastic parts cannot be less than 10% of shrinkage.
4. The surface of the plastic part, in terms of the range that the molding material can cover, the surface structure of the visible surface of the plastic part should be molded at the contact point with the mold. If possible, the smooth surface of the plastic part should not be in contact with the mold surface. It's like using a female mold to make a bathtub and washing tub.
5. Modification, if you use a mechanical horizontal saw to cut off the clamping edge of the plastic part, there must be at least 6-8mm margin in the height direction. Other dressing work, such as grinding, laser cutting or jet, must also be left over. The gap between the cutting lines of the knife edge die is the smallest, and the distribution width of the punching die is also small when trimming. These should be paid attention to.
6. Shrinkage and deformation, plastics are easy to shrink (such as PE), some plastic parts are easy to deform, no matter how to prevent them, 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 mold parts. For example: Although the wall of the plastic part remains straight, its reference center has deviated by 10mm; the mold base can be raised to adjust the shrinkage of this deformation.
7. The amount of shrinkage, the following shrinkage factors must be considered when manufacturing the blister mold. ① The molded product shrinks. If you can't clearly know the shrinkage rate of the plastic, you must take a sample or use a mold of similar shape to get it through experiments. Note: Only the shrinkage rate can be obtained by this method, but the deformation size cannot be obtained. ② Shrinkage caused by the adverse effects of intermediate media, such as ceramics and silicone rubber. ③ The shrinkage of the material used in the mold, such as the shrinkage when casting aluminum.

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