1. Mold design
Strictly control the production and manufacturing standards of the mold, and pay attention to the following aspects from the initial design stage:
1. Fully understand the mold structure, material, hardness, precision and other requirements, and reasonably analyze whether the shrinkage rate of the molded plastic material is correct? Is the product 3D size modeling complete?
2. Fully consider the possible problems of injection molded products, such as shrinkage, flow mark, draft angle, weld line and cracks.
3. Simplify the mold processing steps under the premise that the functions and patterns of injection molded products are not affected.
4. Choose a suitable parting surface and carefully check the mold processing steps, the appearance of the molding and the deburring of the product.
5. Select the proper ejection method, such as push rod, discharge plate, push sleeve, etc., and check whether the position of the push rod and discharge plate is appropriate.
6. Check whether the side core pulling mechanism is suitable to ensure that its operation is not stuck, flexible and reliable.
7. Select the appropriate processing temperature for different injection molded products, and check whether the size, number, and location of the coolant holes are appropriate.
8. Use appropriate material channel and inlet size to determine the location and size of the gate.
9. Select appropriate heat treatment process for modules and cores to avoid deformation.
10. Check whether the injection volume, injection pressure and clamping force of the injection molding machine are sufficient. In addition, it depends on whether the nozzle of the injection molding machine and the aperture of the sprue sleeve match.
2. Manufacturing
Although comprehensive and adequate considerations have been made in the design stage of injection molded products, many problems and difficulties will still arise in actual production, so operators need to adopt more effective, economical and reasonable processing techniques in actual processing.
1. Make 2D and 3D processing plans and choose economical and practical machine tools for production.
2. In the manufacturing process, appropriate tooling and fixtures can be used for auxiliary preparation work. For example, the rational use of tools can prevent product deformation and avoid fluctuations in product shrinkage, thereby further improving product accuracy and reducing errors.
3. The following are the causes of the dimensional errors of molded parts of the British Plastics Association (BPF) and the distribution of their proportions:
A: Mold manufacturing error accounts for about 1/3
B: The error caused by mold wear accounts for about 1/6
C: The error caused by the unbalanced shrinkage rate of molded parts accounts for about 1/3
D: The error caused by the inconsistency between the predetermined shrinkage rate and the actual shrinkage rate accounts for about 1/6
The total error=A+B+C+D. In order to ensure that the geometric dimensions of the molded part meet the relevant regulations, the mold manufacturing tolerance should be less than 1/3 of the molded part's dimensional tolerance.
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