Warpage prediction of the injection-molded strip-like plastic parts

For most strip-like plastic injection molded parts,whose cross section size is much smaller than their length,the traditional Hele-Shaw model and three-dimensional model do not work well in the prediction of the warpage because of their special shape.A new solution was suggested in this work.The strip-like plastic part was regarded as a little-curved beam macroscopically,and was divided into a few one-dimensional elements.On the section of each elemental node location,two-dimensional thermal finite element analysis was made to obtain the nonuniform thermal stress caused by the time difference of the solidi fication of the plastic melt in the mold.The stress relaxation,or equivalently,strain creep was dealt with by using a special computing model.On the bases of in-mold elastic stress,the final bending moment to the beam was obtained and the warpage was predicted in good agreement with practical cases.

For most strip-like plastic injection molded parts, whose cross section size is much smaller than their length, the traditional Hele-Shaw model and three-dimensional model do not work well in the prediction of the warpage be- cause of their special shape. A new solution was suggested in this work. The strip-like plastic part was regarded as a little-curved beam macrnscopically, and was divided into a few one-dimensional elements. On the section of each elemental node location, two-dimensional thermal finite element analysis was made to obtain the non- uniform thermal stress caused by the time difference of the solidification of the plastic melt in the mold. The stress relaxation, or equivalently, strain creep was dealt with by using a special computing model. On the bases of in-mold elastic stress, the final bending moment to the beam was obtained and the warpage was predict- ed in good a^reement with practical cases.