Abstract:

The migration phenomenon of the melt flow front of multi-cavity micro injection molding process within the cavity is observed and analyzed using temperature measuring system equipped of integration of thermocouple sensor and visualization holographic tracer technique. The experimental results show that in the injection rate of 140-220 mm·s^-1, the plastic melt front in the main runner is“U flow state”, while it is upper offset within secondary runner; in the injection rate of 10-70 mm·s^-1, the plastic melt front in the main runner is“fountain” flow state, while it is down offset within secondary runner; and in the injection rate of 80-120 mm·s^-1, the plastic melt fronts within both main and secondary runners have no obvious offset. The results indicate that the injection speed is different during the micro injection molding, leading to various shear heat and also melt front offset. Therefore, a nonequilibrium flow coefficient λ is introduced to determine the flow of the melt front and offset.

Key words: melt, offset, injection rate, micro injection

摘要：

采用集成式热电偶传感器温度测量系统和可视化全息示踪技术, 对多型腔微注塑成型过程熔体流动前沿在型腔内的偏移现象进行观察和分析。结果表明, 当注射速度为140~220 mm·s^-1时, 主流道内的塑料熔体前沿呈“U型流”状态分布, 分流道内塑料熔体前沿向上侧偏移;当注射速度为10~70 mm·s^-1时, 主流道塑料熔体前沿呈“喷泉流”状态分布, 分流道熔体前沿向下侧偏移;当注射速度为80~120 mm·s^-1时, 主流道和分流道熔体前沿均没有明显的偏移。说明微注塑时注射速度不同, 产生的剪切热也不同, 熔体前沿偏移情况也不同。为此, 引入非平衡流动系数λ, 来判断熔体前沿的流动和偏移情况。

关键词: 熔体, 偏移, 注射速度, 微注塑