Injection mold industry is the basic industry of manufacturing industry and the basis of technology transformation. At the same time, it is also an important field of high-tech industry. In industrialized countries such as Europe and the United States, it is known as the "magnetic industry" that "points iron to gold". American industry believes that "injection mold industry is the cornerstone of American industry"; Germany regards it as the "key industry" of all industries. Japan Mold Association also believes that "mold is the driving force of social prosperity" and "the driving force of the whole industrial development"“ "Secret" is "the motive force to enter the affluent society". The following injection mold manufacturers explain the 17 rules of injection mold design for you.

1. Injection mold opening direction and parting line

The opening direction and parting line of each injection product must be determined at the beginning of design to minimize the core pulling slider mechanism and eliminate the influence of parting line on appearance.

① After determining the opening direction, the rib, buckle, protrusion and other structures of the product shall be designed so as to make it as consistent with the opening direction as possible, so as to avoid pulling the core and reducing the suture, and extending the service life of the product.

② After determining the opening direction, the appropriate parting line can be selected to avoid undercutting in the opening direction, so as to improve the appearance and performance.

2. Draft angle of injection mold

① Appropriate demoulding angle can avoid the fuzzing (wire drawing). The demoulding slope of smooth surface should be greater than or equal to 0.5 degree, the surface of fine leather knife (sand surface) should be greater than 1 degree, and the surface of coarse leather knife should be greater than 1.5 degree.

② Proper demoulding slope can avoid top damage, such as top white, top deformation and top fracture.

③ When designing products with deep cavity structure, the slope of the outer surface should be greater than that of the inner surface as far as possible, so as to ensure that the mold core does not deflect during injection molding, obtain uniform product wall thickness, and ensure material strength.

4. Stiffener

① Reasonable use of stiffeners can increase the stiffness of products and reduce deformation.

② The thickness of the stiffener must be less than (0.5 ~ 0.7) t of the product wall thickness, otherwise it will cause surface shrinkage.

③ The inclination of one side of the rib should be greater than 1.5 °， To avoid top damage.

5. Fish fillets

① Too small fillet may lead to stress concentration in the product and lead to product cracking.

② If the fillet is too small, the stress will be concentrated in the cavity and the cavity will break.

③ Setting reasonable fillet can also improve the processing technology of the mold. For example, the cavity can be milled directly with R milling cutter to avoid low efficiency of electrical machining.

④ Different fillets can cause the parting line to move. Choose different fillets or clear angles according to the actual situation.

6. Hole

① The shape of the hole shall be as simple as possible, usually round.

② The axial direction of the hole is consistent with the opening direction, which can avoid the core pulling.

③ When the length diameter ratio of the hole is greater than 2, the demoulding slope should be set. In this case, the diameter of the hole should be calculated according to the small diameter (Zui large physical size).

④ Generally, the length width ratio of blind hole is not more than that of anti hole pin punching.

⑤ The distance between the hole and the edge of the product is usually greater than the hole size.

7. Core pulling slider mechanism of injection mold and its avoiding method

① When plastic parts can not be demoulded smoothly in the open direction, a core pulling slider mechanism should be designed. The slider of core pulling mechanism can form complex product structure, but it is easy to cause defects such as product stitching and shrinkage, and increase the cost of die and shorten the die life.

② When designing injection products, if there are no special requirements, the core pulling structure should be avoided as far as possible. For example, a method such as core collision is used to change the direction of the hole axis and rib to the direction of the mold opening.

8. One piece hinge

① Using the toughness of PP material, the hinge can be designed to integrate with the product.

② The film used as hinge shall be less than 0.5mm in size and uniform.

③ When the integral hinge is injected, the gate can only be designed on one side of the hinge.

9. Insert

① Inserting inserts into injection products can improve local strength, hardness and dimensional accuracy, and set small threaded holes (shafts) to meet various special needs. At the same time, it will increase the cost of products.

② Inserts are usually copper and can be other metal or plastic parts.

③ The part of the insert embedded in the plastic shall be designed with anti rotation and anti pull-out structure. Such as: knurling, opening, bending, flattening, shoulder, etc.

④ The plastic around the insert should be properly thickened to prevent plastic stress cracking.

⑤ When designing inserts, please consider the positioning method (hole, pin, magnetism) in the mold.

10. Logo

The product logo is usually set on the relatively flat inner surface of the product and is convex. Select the surface whose normal direction and opening direction ruler may be the same to set the mark to avoid deformation.

11. Precision of injection parts

Because of the non-uniformity and the uncertainty of shrinkage in the process of injection molding, the precision of injection parts is obviously lower than that of metal parts. The dimensional tolerance of mechanical parts can not be simply applied. The appropriate tolerance requirements should be selected according to the standard. China also issued GB / t14486-93 "dimensional tolerance of engineering plastics molded plastic parts" in 1993. Designers can determine the dimensional tolerance of parts according to the requirements of plastic raw materials and parts and the provisions of parts. Standards. At the same time, it is necessary to determine the appropriate design tolerance accuracy according to the comprehensive strength of the factory and the design accuracy of peer products.

12. Deformation of injection molding parts

Improve the structural rigidity of injection products and reduce deformation. Try to avoid flat structure, reasonable settings flanging, uneven structure. Reasonable stiffeners should be set.

13. Deduction

① The buckle device is designed to share multiple buckles at the same time, so that the whole device will not be unable to use due to the damage of a single buckle, thus prolonging its service life, and adding more filters and fillets to increase the strength.

② The tolerance requirements for the relevant dimensions of the retaining ring are very strict. Too much undercut position may damage the buckle; On the contrary, if the undercut position is too small, the assembly position is difficult to control or the assembly parts are too loose. The solution is to keep a way to change the mold and add glue easily.

14. Welding (hot plate welding, ultrasonic welding, vibration welding)

① Welding can improve the connection strength.

② Welding can simplify product design.

15. Reasonable consideration of the contradiction between process and product performance

① When designing injection products, we must consider the contradiction between appearance, performance and process. Sometimes a part of manufacturability is sacrificed in order to obtain good appearance or performance.

② When the structural design can not avoid injection defects, please try to make the defects appear in the hidden part of the product.

16. Relationship between stud diameter and tapping screw diameter

Self tapping screw hole diameter:

M2：1.7mm

M2.3：2.0mm

M2.6：2.2mm

M3：2.5mm

17. Boss design principle:

① Pillars should not be used alone as far as possible. It should be attached to the outer wall or used with stiffeners as far as possible. The purpose is to enhance the strength of the pillar and make the rubber flow more smoothly.

② The height of the column is usually not more than two and a half times the diameter of the column. Too high column will cause air retention during plastic parts forming (too long length will cause pores, scorch, insufficient filling, etc.).

③ If the height of the column is more than two and a half times the diameter of the column, especially the column far away from the outer wall, the method of strengthening the column strength is to use stiffeners.

④ Boss's shape is mainly round, other shapes are not easy to process.

⑤ The boss should not be too close to the corner or the outer wall, and should keep a certain distance from the outer wall of the product.

⑥ Part of the pulp around the boss can be removed (i.e. opening the crater) to prevent shrinkage and sinking.

⑦ Draft angle of boss: usually 0.5 on the outside °， Internal 0.5 ° Or 1.