In-situ monitoring of polymer flow temperature and pressure in extrusion based additive manufacturing
In-situ monitoring of polymer flow temperature and pressure in extrusion based additive manufacturing
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DOI：
10.1016/j.addma.2019.01.002
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发表时间：
2019-03-01
影响因子：
11
通讯作者：
Bortner, Michael J.
中科院分区：
文献类型：
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作者：
Anderegg, David A.;Bryant, Hunter A.;Bortner, Michael J.
我们展示了一种新型的熔丝制造(FFF)喷嘴设计，能够测量FFF喷嘴内的现场条件，这对于确保聚合物挤出物在零件制造过程中以合适的温度和流量流动至关重要。使用改进的Monoprice Maker Select 3D打印机对ABS长丝进行测试。使用打印机默认温度控制设置的现场测量显示，打印过程中温度下降11摄氏度，压力显著波动，空闲时波动+/-2摄氏度和+/-14千帕。在较低的流量下，这些偏差通过适当校准的比例积分导数(PID)系统来消除。在测试的最高流速下，可以观察到熔体温度降低高达6.5摄氏度，即使使用适当校准的PID，也可以关键地洞察到流速和PID校准对FFF喷嘴内的实际聚合物熔体温度的重要性。测量的压力读数范围从140到6900 kpa，范围为灯丝进料速度和相应的挤出流量。现场压力测量结果高于使用幂定律流体模型的理论预测值，这表明用于理论计算的假设可能不能完全捕捉到FFF液化器中的动力学。我们的喷嘴样机成功地测量了FFF喷嘴的内部条件，从而为打印过程提供了许多重要的见解，这对于监控和改进FFF打印部件至关重要。
We demonstrate a novel Fused Filament Fabrication (FFF) nozzle design to enable measurements of in-situ conditions inside FFF nozzles, which is critical to ensuring that the polymer extrudate is flowing at appropriate temperature and flow rate during the part build process. Testing was performed with ABS filament using a modified Monoprice Maker Select 3D printer. In-situ measurements using the printer's default temperature control settings showed an 11 degrees C decrease in temperature and significant fluctuation in pressure during printing as well as fluctuations while idle of +/- 2 degrees C and +/- 14 kPa. These deviations were eliminated at lower flow rates with a properly calibrated proportional-integral-derivative (PID) system. At the highest tested flow rates, decreases in melt temperature as high as 6.5 degrees C were observed, even with a properly calibrated PID, providing critical insight into the significance of flow rate and PID calibration on actual polymer melt temperature inside the FFF nozzle. Pressure readings ranging from 140 to 6900 kPa were measured over a range of filament feed rates and corresponding extrusion flow rates. In-situ pressure measurements were higher than theoretical predictions using a power-law fluid model, suggesting that the assumptions used for theoretical calculations may not be completely capturing the dynamics in the FFF liquefier. Our nozzle prototype succeeded in measuring the internal conditions of FFF nozzles, thereby providing a number of important insights into the printing process which are vital for monitoring and improving FFF printed parts.