In the field of precision injection mold design, the design of the demolding angle is a crucial aspect. It directly relates to whether plastic products can be smoothly demolded and the quality of the finished products. Reasonable design of the demolding angle can not only effectively avoid difficulties in product demolding but also improve production efficiency and reduce the scrap rate. The following will elaborate on the design key points of the demolding angle for plastic products in precision injection molds from multiple aspects.
Design of Demolding Angle for the Main Body of Products
For products molded by precision injection molds, sufficient demolding angles should be designed on their inner and outer surfaces along the demolding direction. This is the basis for ensuring smooth product demolding. If the demolding angle is insufficient, the product is very likely to be obstructed by the mold during the demolding process, resulting in difficulties in demolding and even defects such as scratches and deformation on the product surface. Generally, the demolding angle of precision injection molds is designed to be 1 – 1.5°. However, when there are special usage requirements for plastic injection products, the demolding taper needs to be specially adjusted. For example, the outer surface of plastic products can adopt a demolding taper of 5′, while the inner surface can adopt a demolding taper of 10′ – 20′. In addition, when the height of the plastic part is relatively small, since the demolding resistance is relatively small, a demolding angle can also not be designed to simplify the mold structure.
Design of Demolding Angle for Special Structures
- Taper Design of Reinforcing Ribs: Reinforcing ribs on plastic parts enhance the strength of the product while also having an impact on demolding. To ensure that the reinforcing ribs can be smoothly demolded, a taper of 4 – 5° should be designed on one side of the reinforcing ribs. This taper design can not only meet the strength requirements of the reinforcing ribs but also avoid damage to the product due to excessive friction between the reinforcing ribs and the mold during the demolding process.
- Taper Design of Hole Structures: If there are hole structures on plastic parts along the demolding direction, the demolding resistance will be significantly increased. To reduce this resistance, a taper of 4 – 5° should be adopted around the holes. By setting a taper, the holes can gradually separate from the mold during the demolding process, reducing the friction force and achieving smooth demolding.
- Taper Design of Side Walls with Leather Patterns: When the side walls of plastic parts have leather patterns, since the patterns will increase the friction force between the product and the mold, a relatively large demolding taper of 4 – 6° should be designed. A larger demolding taper can provide sufficient demolding space for the product and avoid difficulties in demolding due to the close adhesion between the patterns and the mold.
Design of Demolding Angle for Product Retention Control
During the mold opening of precision injection molds, sometimes it is necessary to make the plastic products remain in the front mold or the rear mold. To achieve this goal, the method of adjusting the demolding angle can be adopted. Specifically, the demolding angle on the side where it is hoped that the product will remain can be deliberately reduced, or the angle on the opposite side can be increased. Through this differential angle design, the friction force distribution between the product and the front and rear molds is changed, making it easier for the product to remain on the specified mold side.
Design of Demolding Angle for Deep – Cavity Products
For plastic products with a relatively large depth, during the injection molding process, not only do the front and rear molds need to have sufficient demolding angles, but the taper of the moving mold should also be greater than that of the fixed mold as much as possible. This design method can make the side wall thickness of the lower part of the plastic part larger than that of the upper part. When the precision injection mold is closed, due to the greater pressure on the upper part, the density of the upper part of the plastic part can be ensured, thereby improving the overall quality of the product. At the same time, the larger side wall thickness of the lower part is also conducive to the demolding of the product and reduces the damage to the product during the demolding process due to insufficient strength.
In conclusion, the design of the demolding angle for plastic products in precision injection molds is a process that comprehensively considers multiple factors. Designers need to reasonably determine the size and distribution of the demolding angle according to the specific structure, usage requirements, and molding process characteristics of the product to ensure that the product can be smoothly demolded and meet the quality requirements.
