When designing each injection product, the opening direction and parting line should be determined first to minimize the core pulling slider mechanism and eliminate the influence of the parting line on the appearance.
1. After the opening direction is determined, the structure of strengthening ribs, buckles, bumps and other structures should be designed to be consistent with the opening direction as much as possible, in order to avoid core pulling, reduce stitching lines and extend the life of the mold.
2. After the opening direction is determined, the appropriate parting line can be selected to avoid reverse buckling in the opening direction and improve appearance and performance.
1. Proper demolding slope can prevent product fuzziness. The demolding slope of smooth surface should be ≥0.5 degrees, the demolding slope of fine grain (sand surface) should be greater than 1 degree, and the demolding slope of rough grain surface should be greater than 1.5 degrees.
2. Proper demolding slope can prevent product top injury, such as top white, top deformation, and top breakage.
3. When designing products with deep cavity structure, the slope of the outer surface should be greater than that of the inner surface to ensure that the mold core is not offset during injection, and the product wall thickness is uniform, and the material strength at the opening of the product is guaranteed.
1. Various plastics have a certain wall thickness range, generally 0.5-4mm. When the wall thickness exceeds 4mm, it will cause problems such as long cooling time and shrinkage marks, and the product structure should be considered to be changed.
2. Uneven wall thickness will cause surface shrinkage.
3. Uneven wall thickness will cause pores and weld marks.
1. The reasonable application of reinforcement ribs can increase product rigidity and reduce deformation.
2. The thickness of reinforcing ribs must be ≤ (0.5-0.7) T product wall thickness, otherwise it will cause surface shrinkage.
3. The one-sided slope of the reinforcement rib should be greater than 1.5° to avoid top injury.
1. Too small a fillet may cause stress concentration in the product, leading to product cracking.
2. Too small a fillet may cause stress concentration in the mold cavity, leading to mold cavity cracking.
3. Setting reasonable fillet can also improve the processing technology of the mold, such as the cavity can be machined directly by R cutter, and avoid inefficient electric machining.
4. Different fillet may cause the parting line to move, and different fillet or clearance should be selected based on the actual situation.
1. The shape of the hole should be as simple as possible, generally taking a circular shape.
2. The axial direction of the hole should be consistent with the opening direction, which can avoid core pulling.
3. When the length to diameter ratio of the hole is greater than 2, a demolding slope should be set. At this time, the diameter of the hole should be calculated according to the small size (the maximum solid size).
4. The length to diameter ratio of the blind hole is generally not more than 4.
5. The distance between the hole and the edge of the product is generally greater than the size of the hole.
1. When the plastic part cannot be demolded smoothly in the opening direction, the core pulling slider mechanism should be designed. The core pulling mechanism slider can form complex product structures, but it is easy to cause defects such as stitching lines and shrinkage, and increase the mold cost and shorten the mold life.
2. When designing injection products, if there is no special requirement, try to avoid core pulling structure. For example, the hole axis and rib direction are changed to the opening direction, and the cavity and core are touched and penetrated.