[中文]收縮痕
一、注塑件缺陷的特征
通常与表面痕有关,而且是塑料从模具表面收缩脱离形成的。
二、可能出现问题的原因
(1).熔融温度不是太高就是太低。
(2).模腔内塑料不足。
(3).冷却阶段时接触塑料的面过热。
(4).流道不合理、浇口截面过小。
(5).模温是否与塑料特性相适应。
(6).产品结构不合理(加强筋过高,过厚,明显厚薄不一).
(7).冷却效果不好,产品脱模后继续收缩。
三、补救方法
(1).调整射料缸温度。
(2).调整螺杆速度以获得正确的螺杆表面速度。
(3).增加注塑量。
(4).保证使用正确的垫料;增加螺杆向前时间;增加注塑压力;增加注塑速度。
(5).检查止流阀是否安装正确,因为非正常运行会引致压力流失。
(6).降低模具表面温度。
(7).矫正流道避免压力损失过大;根据实际需要,适当扩大截面尺寸。
(8).根据所用塑料的特性及产品结构适当控制模温。
(9).在允许的情况下改善产品结构。
(10).设法让产品有足够的冷却。
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[外文]Sink marks
I. Features of injection molding defects
Generally related to marks on the surface and resulted from coming off from the mold surface due to shrinking.
II. Possible causes
(1) Too high or too low melt temperature.
(2) Insufficient material in the cavity
(3) The contact surface of mold with the plastic is too hot during the cooling procedure.
(4) Improper runner design, too small gate section.
(5) Mold temperature unfit for plastic′s properties.
(6) Improper product structure (The rib stiffeners are too high, too thick and significantly inconsistent in thickness.)
(7) Poor cooling result. The product continues to shrink after being ejected.
III. Remedies
(1) Vary the temperature in the barrel
(2) Vary the velocity of screw to obtain the proper screw surface velocity.
(3) Increase the injection amount.
(4) Ensure to use proper padding; Increase the forward time of screw; Increase the injection pressure; Increase the injection speed.
(5) Check the stop valve to be sure it′s properly mounted.
(6) Decrease the temperature at the surface of mold.
(7) Correct the runner to avoid too much loss of pressure. Increase the section size accordingly depending on actual demands.
(8) Control the mold temperature applicably depending on the properties of plastic and structure of product.
(9) Improve the structure of product if allowed.
(10) Manage to let the product cool sufficiently.
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