Warping and deformation of injection products are very difficult problems. It should be solved mainly from the mold design, while the adjustment effect of forming conditions is very limited.
The causes and solutions of warpage and deformation can refer to the following items:
(1) When the deformation is caused by the residual stress caused by the molding conditions, the stress can be eliminated by reducing the injection pressure, increasing the mold and making the mold temperature uniform, increasing the resin temperature or adopting the annealing method.
(2) When the stress deformation is caused by poor demoulding, it can be solved by increasing the number or area of push rods and setting the demoulding slope.
(3) If the cooling method is not suitable and the cooling is uneven or the cooling time is insufficient, the cooling method can be adjusted and the cooling time can be extended. For example, the cooling circuit can be set as close to the deformation as possible.
(4) For the deformation caused by forming shrinkage, it is necessary to modify the mold design. The most important thing is to keep the wall thickness of the product consistent. Sometimes, as a last resort, we have to measure the deformation of the product and trim the mold in the opposite direction to correct it. For resins with large shrinkage, the deformation of crystalline resins (such as polyformaldehyde, nylon, polypropylene, polyethylene and PET resins) is greater than that of non-crystalline resins (such as PMMA resin, PVC, polystyrene, ABS resin and AS resin). In addition, due to the fiber orientation of glass fiber reinforced resin, the deformation is also large.