The injection mold design process, product deformation is an important factor mold engineers must consider. Hot melt plastic injection molding outer mold cooling stereotypes and cooling process, inevitably deformation, affecting the product resulting in a large number of precision molding waste occurs.
Deformable plastic products mainly in two forms: shrinkage and warpage. Shrinkage refers to the product size with respect to the difference in terms of the presence of the mold cavity dimensions; warpage refers to the shape of the article deviates from the shape of the mold cavity.
In order to reduce shrinkage deformation, mold engineers often split before the mold cavity to compensate for shrinkage of the molding material to product model, so that the product size after being deformed as close as possible design size. Currently, many large injection mold CAD commercial software has the function of setting shrinkage, and can be set according to different situations in different directions shrinkage. The essence of this method is to reverse the shrinkage products pre-compensation. I believe that reducing warpage, you can also use this method.
Vehicle fan deformation characteristics
Car fan shape shown in Figure 1. Fans from the inner, outer and six blade composition, the overall structure was shaped spokes. A larger ventilation area uneven distribution of the material connection between the inner and outer blade, so it is in the article, the outer ring, or in the uneven thickness of the blade, and shrinkage occurs Alice Qu deformation.
In contrast, the inner and outer ring warping deformation is small, mainly in the form of two parts deformation performance in shrinkage. Blades and the inner and outer rings, as both exist shrinkage, warpage also exist, is the largest part of the fan warpage, so when considering the deformation of the blade, must consider shrinkage and warpage.
According to the characteristics of the fan gate provided at the center of the article. Forming material selection PA66 / GF30, which is a very prone to warpage of plastic. Statistics show [1], a 200mm × 200mm × 2.5mm of PA66 / GF30 plate member, up to the maximum warpage 10.9mm. Because warpage is too large, the product has conducted two mold design. In the first mold design process, because only products for pre-compensating shrinkage, warpage not be expected to handle blade deformation, resulting in the front blade trailing edge warpage is too large, can not meet the design requirements of customers drawings . This article is an automotive engine cooling system, the key components, production volume, stringent quality requirements. After more than a year of repair mode, test mode, the final product is not satisfactory precision molding. Even in the production process, the products pass rate is only 86%.
