Pellet Extruder-based Industrial 3D Printer for Custom-fit Military Respirators and Continuous Positive Airway Pressure Masks using Soft Thermoplastic Elastomers.

增材制造（AM）技术已经成为第四次工业革命（工业4.0）的核心组成部分。在其他类型的增材制造技术中，挤出增材制造技术提供了修改打印头的潜力，允许在高温下熔化的工程聚合物的多材料打印。大多数商业上可用的挤出AM系统（或3D打印机）使用聚合物长丝作为原料，并且仅限于刚性或半刚性聚合物。这些系统不能打印软聚合物。一些商业挤出AM系统包括一个小颗粒挤出机直接安装在打印头。这些基于挤出机的颗粒提供了打印软聚合物的潜力；然而，这些系统要么表现出非常慢的打印速度（~ 100克/小时），要么表现出粗糙的打印分辨率（~ 400微米）。由于这些系统在打印头中没有主动流量控制机制，因此限制了它们在工业应用中的适用性。最近，我们的团队开发了一种新技术，熔融颗粒打印（FPP），它允许3D打印极其柔软、可拉伸的聚合物。该技术还可以直接从原料颗粒中打印软质和刚性热塑性塑料的多材料，打印速度显著提高（~ 1公斤/小时），适用于工业应用。使用FPP技术成功打印的软聚合物具有类似于人类肌肉的刚度。因此，它开辟了一个新的应用领域，这是以前由于打印软聚合物的限制而无法实现的。例如，军事人员在战场上被要求长时间佩戴呼吸器，这往往会造成不适并限制他们的表现。不仅如此，睡眠呼吸暂停患者在夜间睡眠时还需要佩戴持续气道正压通气面罩。军用呼吸器和CPAP口罩都可能引起痛苦，因为它们不是个性化的，而是为特定用户设计的。由于我们的技术允许3D打印软聚合物，定制的呼吸器和口罩可以通过3D扫描用户的脸来3D打印，这将大大提高它们的性能和舒适度。

Additive manufacturing (AM) technology has emerged as a core component of the fourth industrial revolution (Industry 4.0). Among other types of AM technologies, extrusion AM technology offers the potential to modify the print-head, allowing multi-material printing of engineering polymers that melts at an elevated temperature. Most of the commercially available extrusion AM systems (or 3D printers) use polymer filaments as feedstock and are limited to only rigid or semi-rigid polymers. These systems can not print soft polymers. Some commercial extrusion AM systems consist of a small pellet extruder directly mounted on the print-head. These pellet extruder-based offer potential to print soft polymers; however, these systems exhibit either a very slow print speed (~ 100 g/hour) or a coarse print resolution (~ 400 µm). Because these systems do not have an active flow control mechanism in their print heads, thus limit their suitability for industrial applications. Recently our team has developed a new technology, fused pellets printing (FPP) which allows 3D printing of extremely soft, stretchable polymers. This technology also enables multi-material printing of both soft and rigid thermoplastics directly from raw pellets at a significantly higher print speed (~ 1 kg/hour) suitable for industrial applications. The soft polymer that has been successfully printed using FPP technology has a stiffness similar to the human muscle. Therefore, it opens up a new horizon of applications that were not possible before because of the limitation to print soft polymers. For instance, military personnel is required to wear respirators on the battlefields for a prolonged period which often creates discomfort and limits their performance. Not only that but the patients with sleep apnea are also required to wear continuous positive airway pressure (CPAP) masks during nighttime sleeping. Both the military respirator and CPAP masks can cause distress because they are not personalized and designed to serve the specific user. Since our technology allows 3D printing of soft polymers, custom-fit respirators and masks can be 3D printed by 3D scanning the user's face which will significantly enhance their performance and comfort.