Warping deformation is one of the common defects in injection molding of thin shell plastic parts, because it involves guessing the amount of warping deformation, and the warping deformation rules of injection molded parts with different data and shapes are very different. When the warping deformation exceeds the allowable error, it will become a forming defect, and then affect the product installation. It is a useful condition for controlling warpage defects to guess the warpage deformation of many increasing thin-walled parts (wall thickness less than 2mm). Qualitative analysis is mostly used for warping deformation analysis, and measures are taken from the aspects of product planning, mold planning and injection molding process conditions to prevent large warping deformation as far as possible.

Moulds

The position, 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, the greater the internal stress caused by the moving and feeding between the frozen layer and the central active layer; On the contrary, the shorter the moving distance, the shorter the moving time from the gate to the moving end of the workpiece, the thinner the frozen layer thickness during mold filling, the lower the internal stress, and thus the warpage deformation will be greatly reduced. If only one center 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, warping deformation can be effectively prevented.

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

In addition, the application of multiple gates can also shorten the plastic activity ratio (L / T), and then make the material density in the mold cavity more uniform and shorten more uniformly. At the same time, the whole plastic part can be filled under small injection pressure. Smaller injection pressure can reduce the tendency of molecular orientation of plastic, reduce its internal stress, and thus reduce the deformation of plastic parts.

Moulds温度：模具温度对制品的内涵功用和表观质量影响很大。模具温度的凹凸决定于塑料结晶性的有无、制品的尺度与结构、功用要求，以及其它工艺条件（熔料温度、打针速度及打针压力、模塑周期等）

Source: Jiangmen engineering plastics http://www.wywantong.com/