Zhenfei mold deformation method of plastic products
First, the deformation of the reasons:
1, the shape of the article, particularly molding shrinkage rates with the relationship between a residual stress caused by the thickness of the article.
2, the residual stress generated due to the molding conditions
3, the residual stress generated when the release
4, due to insufficient cooling time caused by the deformation
II. The associated knowledge
1, the reasons for the article deformation (warping, bending, small wrinkles) with the same cracks. That residual stress within the article. Molding conditions should be set towards the elimination of internal stress of setting products. That is, after improving cylinder temperature, mold temperature, the flowability of the material under the good condition, the injection pressure is not too high.
2, in order to reduce residual stress, there is annealed, i.e., below the thermal deformation temperature of 10 degrees, there are more than two hours of heating to eliminate the effect of internal stress. However, due to the annealing of the high cost of this approach is not commonly used.
3, if the cooling water holes of the mold can not be uniformly cooled article, also produce residual stresses, which means that the cooling water can not be too shallow hole.
Third, the solution.
An instant: in the mold sufficiently cooled and solidified (prolonged cooling time timer), raise the barrel temperature, lower injection pressure.
2. Short-term: the mold to cool uniform.
3. Long-term: to avoid differences in product thickness, set the gate in product thickness big place (1-1), due to the linear prone to warping, made a big R curve, reversible bending mold products, increasing the ejection lever months the number increased stripping slope.
Fourth, the material differences:
1, the crystalline material (polyethylene, polypropylene, polyoxymethylene, nylon) molding shrinkage, as well as easy to cause biased, non-crystalline material (polystyrene, ABS) easily lead to residual stresses.