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Golden Rules For Mold Design-2

Integrated hinge

  1. Taking advantage of the toughness of PP material, the hinge can be designed to be integrated with the product.
  2. The size of the film used as a hinge should be less than 0.5mm and kept uniform.
  3. When injection molding an integrated hinge, the gate can only be designed on one side of the hinge.
  4. Inserts
  5. Inserting inserts into injection molded products can increase local strength, hardness, dimensional accuracy and set up small threaded holes (shafts) to meet various special needs. It will also increase product costs.
  6. The insert is generally copper, but can also be other metal or plastic parts.
  7. The part of the insert embedded in the plastic should be designed with anti-rotation and anti-pull-out structures. Such as: knurling, holes, bending, flattening, shoulders, etc.
  8. The plastic around the insert should be appropriately thickened to prevent stress cracking of the plastic parts.
  9. When designing inserts, full consideration should be given to their positioning methods in the mold (holes, pins, magnetism)
  10. Logo

Product logos are generally placed on the flat inner surface of the product in a raised form. Choosing a surface where the normal direction may be consistent with the mold opening direction can avoid strain.

  1. Precision of injection molded parts

Due to the unevenness and uncertainty of shrinkage during injection molding, the accuracy of injection molded parts is significantly lower than that of metal parts. The dimensional tolerances of mechanical parts cannot simply be applied and appropriate tolerance requirements should be selected according to standards. my country also issued GB/ T14486-93 “Dimensional Tolerances of Engineering Plastics Molded Plastic Parts”, designers can determine the dimensional tolerance of parts according to the plastic raw materials used and the requirements for the parts, and according to the provisions of the standard. At the same time, the appropriate design tolerance accuracy must be determined based on the comprehensive strength of the factory and the design accuracy of peer products.

  1. Deformation of injection molded parts

Improve the rigidity of the injection molded product structure and reduce deformation. Try to avoid flat structures and rationally set up flanges and concave-convex structures. Set up reasonable reinforcement ribs.

Thirteen, buckle position

  1. The buckle device is designed to be shared by multiple buckles at the same time, so that the entire device will not be unable to operate due to damage to individual buckles, thereby increasing its service life. Furthermore, multiple filters and rounded corners can be added to increase strength.
  2. The tolerance requirements for the dimensions related to the buckle position are very strict. Too many undercut positions may easily cause damage to the buckle position; conversely, if there are too few undercut positions, the assembly position will be difficult to control or the assembled parts may be too loose. The solution is to reserve a way to easily add glue when modifying the mold.
  3. Welding (hot plate welding, ultrasonic welding, vibration welding)
  4. Welding can improve the connection strength.
  5. Using welding can simplify product design.
  6. Reasonably consider the contradiction between process and product performance
  7. When designing injection molded products, the contradiction between product appearance, performance and process must be comprehensively considered. Sometimes sacrificing part of the craftsmanship can result in good appearance or performance.
  8. When the structural design cannot avoid injection molding defects, try to make the defects occur in hidden parts of the product.
  9. Relationship between screw column hole diameter and self-tapping screw diameter
    Self-tapping screw screw column hole diameter
  10. BOSS design principles:
  11. The pillars should not be used alone. They should be connected to the outer wall or used together with reinforcing ribs. The purpose is to enhance the strength of the pillars and make the rubber flow smoother.
  12. The height of the pillar is generally not more than two and a half times the diameter of the pillar. Because pillars that are too high will cause air to be trapped during molding of plastic parts (too long will cause pores, scorching, insufficient filling, etc.).
  13. If the height of the pillar exceeds two and a half times the diameter of the pillar, especially the pillar far away from the outer wall, the method to strengthen the pillar is to use reinforcing ribs.
  14. The shape of BOSS is mainly round, and other shapes are difficult to process.
  15. The BOSS position should not be too close to the corner or the outer wall, and should be kept at a distance from the outer wall of the product.
    6). Part of the thickness around the BOSS can be removed (i.e., a crater is opened) to prevent shrinkage and subsidence.
    7). BOSS’s mold dialing angle: usually 0.5° for the outside and 0.5° or 1 for the inside.
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