About Mold Design and Development

One. Precautions

   1.The shape and wall thickness of the plastic parts should be designed to facilitate the smooth flow of the material to fill the cavity, and try to avoid sharp corners and gaps.

   2. The draft angle should be large, 1°～2° for 15% glass fiber, 2°～3° for 30% glass fiber. When the demolding slope is not allowed, forced demolding should be avoided, and a horizontal parting structure should be adopted. 

   3. The cross section of the pouring system should be large, and the flow should be straight and short to facilitate uniform fiber dispersion. 

   4. The design of the feed inlet should consider preventing insufficient filling, anisotropic deformation, uneven distribution of glass fibers, and easy to produce weld marks and other undesirable consequences. The feed port should be flakes, wide and thin, fan-shaped, ring-shaped and multi-point feed ports to make the material flow turbulent, and the glass fiber is evenly dispersed to reduce anisotropy. It is best not to use needle-shaped feed ports. The cross section of the mouth can be increased appropriately and its length should be short. 

   5. The mold core and cavity should have sufficient rigidity and strength. 

   6. The mold should be hardened, polished, and wear-resistant steel should be selected, and the easily worn parts should be easy to repair and replace. 

   7. The ejection should be even and strong, easy to replace and repair. 

   8. The mold should be equipped with an exhaust overflow groove, and should be located at a location prone to weld marks.

Two. Mold temperature setting

   1. Mold temperature affects the molding cycle and molding quality. In actual operation, it is set from the lowest appropriate mold temperature of the material used, and then adjusted appropriately according to the quality condition.

   2. Correctly speaking, the mold temperature refers to the temperature of the cavity surface when the molding is performed. In the mold design and the condition setting of the molding process, it is important not only to maintain a proper temperature, but also to make it uniform distributed.

   3. Uneven mold temperature distribution will lead to uneven shrinkage and internal stress, which makes the molding mouth easy to deform and warp.

   4. Increasing the mold temperature can obtain the following effects: 

  ①Increase the crystallinity of the molded product and a more uniform structure. 

  ② Make the molding shrinkage more fully and reduce the post shrinkage. 

  ③Improve the strength and heat resistance of molded products. 

  ④Reduce residual internal stress, molecular alignment and deformation. 

  ⑤Reduce the flow resistance during filling and reduce the pressure loss. 

  ⑥ Make the appearance of the molded product more shiny. 

  ⑦Increase the chance of burrs on molded products. 

  ⑧Increase the near gate part and reduce the chance of recession in the far gate part. 

  ⑨Reduce the obvious degree of bonding line. 

  ⑩Increase the cooling time.