Do you know the basic knowledge of injection mold design?

Do you know the basic knowledge of injection mold design?

Injection mold design needs to pay attention to what points

Product wall thickness

  1. All kinds of plastics have a certain wall thickness range, generally 0.5~4mm, when the wall thickness is more than 4mm, it will cause too long cooling time, shrinkage printing and other problems, should be considered to change the product structure.
  2. Uneven wall thickness will cause surface shrinkage.
  3. 壁厚不均会引起气孔和熔接痕。

To strengthen

  1. The reasonable application of stiffeners can increase product rigidity and reduce deformation.
  2. The thickness of reinforcement must be ≤ (0.5~0.7) T product wall thickness, otherwise it will cause surface shrinkage.
  3. The single-side slope of the reinforcement should be greater than 1.5° to avoid jacking injury.

Rounded corners

  1. Too small rounded corners may cause stress concentration and result in cracking.
  2. Too small rounded corners may cause stress concentration in the mold cavity and lead to cavity cracking.
  3. Setting a reasonable round corner can also improve the mold processing technology, such as the cavity can be directly milling with R knife, and avoid low efficiency of electrical machining.
  4. Different round corners may cause the movement of the parting line, should be combined with the actual situation to choose different round corners or corners of injection mold design what are the basic points of injection mold design what are the basic points.

Die opening direction and parting line

At the beginning of the design of each injection product, the direction of opening and parting line should be determined to ensure that the core pulling slider mechanism is reduced as much as possible and the influence of parting line on the appearance is eliminated.

  1. After the direction of die opening is determined, the stiffeners, buckles, bulges and other structures of the product are designed to be consistent with the direction of die opening as far as possible, so as to avoid core pulling, reduce stitching lines and prolong the life of the die.
  2. After the direction of die opening is determined, THE appropriate parting line can be selected to avoid the inverted direction of die opening, so as to improve the appearance and performance.


  1. Appropriate demoulding incline can avoid product pulling (drawing). The demoulding slope of smooth surface should be ≥0.5 degree, fine skin grain (sand surface) surface is greater than 1 degree, rough skin grain surface is greater than 1.5 degree.
  2. Proper demoulding incline can avoid product top damage, such as top white, top deformation, top broken injection mold design of the basic requirements
  3. 深腔结构产品设计时外表面斜度尽量要求大于内表面斜度,以保证注塑时模具型芯不偏位,得到均匀的产品壁厚,并保证产品开口部位的材料强度


  1. The shape of the hole should be as simple as possible, generally round
  2. The axial direction of the hole is consistent with the direction of the die opening, which can avoid pulling the core.
  3. When the aspect ratio of the hole is greater than 2, the demoulding inclination should be set. In this case, the diameter of the hole should be calculated according to the path size (maximum solid size).
  4. The aspect ratio of the blind hole is generally not more than 4. The anti-hole needle is flushed and bent
  5. The distance between the hole and the edge of the product is generally greater than the aperture size.

Accuracy of injection parts

Due to the inhomogeneity and uncertainty of shrinkage during injection molding, the accuracy of injection parts is significantly lower than that of metal parts, so the dimensional tolerance of mechanical parts cannot be simply applied, and appropriate tolerance requirements should be selected according to the standard. China also released GB/T14486-93 in 1993
“Dimensional Tolerance of Engineering Plastic Molded Plastic Parts”, the designer can determine the dimensional tolerance of the parts according to the requirements of the plastic raw materials and parts used in the standard.
At the same time, according to the comprehensive strength of the factory, the design accuracy of the peer products to determine the appropriate design tolerance accuracy.

Deformation of injection molded parts

Improve the rigidity of injection molding product structure, reduce deformation of the basic points of injection mold design what mold design try to avoid flat structure, reasonable Settings of flanging, concave and convex structure. Set reasonable stiffeners.

Buckle a

  1. The buckle device is designed to be shared by multiple buckle locations at the same time, so that the overall device will not be unable to operate because of the damage of individual buckle locations, thus increasing its service life, and then more test filter plus rounded corners, increasing strength
  2. The tolerance requirements of the relevant dimensions of the buckle are very strict, and too many reverse buckle positions are easy to form buckle damage; On the contrary, if the inverted position is too few, the assembly position is difficult to control or the combination part is too loose. The solution is to reserve the mold easy to add glue to achieve.