As different types of forming molds in Dongguan have been applied in many fields, and the manufacturing technology of professional molds in Dongguan has also undergone certain changes and developments in recent years, the general design rules of vacuum forming molds are summarized in this section.

The design of vacuum forming molds in Dongguan includes aspects such as batch size, forming equipment, precision conditions, geometric shape design, dimensional stability and surface quality.

For large and small batch experiments, when the mold production is small, wood or resin can be used for manufacturing. However, if the experimental mold is used to obtain data related to the shrinkage, dimensional stability and cycle time of the product, a single-cavity mold should be used for the experiment and it should be ensured that it can be applied 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, it is often necessary to comprehensively consider dimensional stability and surface quality. For instance, when the design and dimensional stability of the product require the use of a female die (concave die), but for products with a higher surface gloss requirement, a male die (convex die) is needed. In this case, the plastic part ordering party will take these two points into comprehensive consideration to ensure that the product can be produced under the best conditions. Experience has proved that designs that do not meet the actual processing conditions are often failures.

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 that leaves the mold. If the thickness of the material is required to be changed in the future due to the need for material stiffness, it may result in the conversion of the male mold to the female mold. The dimensional tolerance of plastic parts shall not be less than 10% of the shrinkage rate.

4. For 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 formed at the contact point with the mold. If possible, the smooth surface of the plastic part should not come into contact with the surface of the mold. Just like the situation where a negative mold is used to make bathtubs and laundry basins.

5. Finishing: If a mechanical horizontal saw is used to cut off the clamping edge of the plastic part, there should be at least 6 to 8mm of allowance in the height direction. Other finishing work, such as grinding, laser cutting or jet cutting, must also leave a margin. The gap between the cutting lines of the knife edge die is the smallest, and the distribution width during the trimming of the punching die is also very small. All these points need to be noted.

6. Shrinkage and deformation: Plastics are prone to shrinkage (such as PE), and some plastic parts are prone to deformation. No matter how much prevention is taken, plastic parts will deform during the cooling stage. Under such conditions, the shape of the forming mold needs to be changed to adapt to the geometric deviation of the plastic part. 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 amount of this deformation.

7. Shrinkage: When manufacturing vacuum forming molds, the following shrinkage factors must be taken into consideration. ① Shrinkage of formed products. If the shrinkage rate of the plastic cannot be clearly known, samples must be taken or it can be obtained through experiments using molds of similar shapes. Note: By this method, only the shrinkage rate can be obtained, but not the deformation size. ② Shrinkage caused by the adverse effects of intermediate media, such as ceramics, silicone rubber, etc. ③ Shrinkage of the materials used in the mold, such as shrinkage when casting aluminum.