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Warpage is one of the common defects in injection molding of thin shell plastic parts. Due to the conjecture of warpage deformation, the warpage rules of injection molded parts with different materials and shapes are quite different. When the warpage exceeds the allowable error, it becomes a forming defect, and then affects the product assembly. It is a useful condition for controlling warpage defects to guess the warpage deformation of a large number of thin-walled parts (wall thickness less than 2mm). Qualitative analysis is mostly used in warpage analysis, and measures are taken from product planning, mold planning and injection molding process conditions to prevent large warpage deformation.

Mould

The orientation, method and number of gates of injection mold will affect the filling condition of plastic in the mold cavity, and then lead to the deformation of plastic parts.

The longer the moving distance is, the greater the internal stress caused by the movement and feeding between the frozen layer and the central active layer; on the contrary, the shorter the moving distance is, the shorter the moving time from the gate to the moving end of the part is, and the thickness of the frozen layer is thinner, the internal stress is decreased, and the warpage deformation is greatly reduced. If only one central gate or one side gate is used, the plastic parts will be distorted because the shortening rate in the diameter direction is greater than that in the circumferential direction; if multiple point gates are used, the warping deformation can be effectively prevented.

When point casting is selected for molding, the location and quantity of gates have great influence on the deformation degree of plastic parts due to the heterotropism of plastic shortening Because 30% glass fiber reinforced PA6 is selected, and a large injection molding part with 4.95kg weight is obtained, there are many reinforcing ribs along the moving direction of the surrounding wall, so that each gate can be fully balanced.

In addition, the use of multiple gates can shorten the L / T ratio of plastic, and then make the density of materials in the mold cavity more uniform and shorten more evenly. Together, the entire plastic part can be filled with less injection pressure. The smaller injection pressure can reduce the molecular orientation and internal stress of plastics, thus reducing the deformation of plastic parts.

Mold temperature: mold temperature has a great influence on the connotative function and apparent quality of products. The concavity and convexity of mold temperature depends on the crystallinity of plastics, the size and structure of products, functional requirements, and other process conditions (melt temperature, injection speed and injection pressure, molding cycle, etc.)

Source: Jiangmen engineering plastics http://www.yun-kang.cn/