最近大家都在疯传一个3D打印革命性技术，打印速度可以比现有的所有3D打印机提高100倍。南极熊3D打印网根据调查，现在大多数人都非常看好3D打印，但是往往都会问一个问题：它的打印速度有多快，打印一个东西需多长时间？在很多情况下，速度成为3D打印应用的最大障碍。
革命性技术CLIP让3d打印速度提高100倍，获得4100美金投资，上《science》封面
这两个10厘米高的大白，耗费了大概7个小时
前段时间，3D打印应用平台“熊玩意”上搞感恩送宇宙第一暖男“大白”的活动，想不到引起疯抢，于是熊玩意想增加送大白的数量，无奈打印速度慢，远远不能满足需求。现在有了CLIP的新工艺，可以大大提升这个速度，把数小时的打印时间缩短为仅仅几分钟。
革命性技术CLIP让3d打印速度提高100倍，获得4100美金投资，上《science》封面
UNC-Chapel Hill的研究人员在《科学》(Science)杂志上介绍了这种名为CLIP的新工艺，将其描述为“连续液态界面生产”。他们表示，3D打印有两个非常令人恼火的不足之处：一是要等待好几个小时才能完成制作，二是打印出来的东西表面很粗糙，而这个新方法可以大大改进这两个方面。 CLIP可以在相对很短的时间里打印出顺滑的复杂物品，而且可以使用更多的材料来打印物品。
现有的3D打印工艺使用液态树脂，在一个缓慢的过程中逐层打制作出物品：先打印一层，固化它，补充树脂材料，然后再打印一层，周而复始，直到打印完成。而在CLIP工艺中，一个投影机从下方用紫外线显示连续的、极薄的物品横截面。紫外线在一缸液态树脂中以横截面方式硬化液体。与此同时，一台升降机不断将成形的物体捞出树脂缸。
革命性技术CLIP让3d打印速度提高100倍，获得4100美金投资，上《science》封面
CLIP打印机的关键之处位于树脂缸的底部：那里有一个窗口让氧气和紫外线通过。因为氧气可以阻碍固化过程，缸底的树脂连续形成一个“死区”，不会固化。而这个“死区”非常之薄，只有几个红细胞那么厚。因此紫外线可以通过，并固化其上方没有接触氧气的树脂。不会有树脂粘在缸底，而打印速度变得非常快，因为它不是在空气中，而是在树脂里打印的（在空气中打印，由于氧气存在，固化速度就会减缓）。当打印机捞起成形的物品时，吸嘴会往缸底添加低氧树脂。
CLIP不仅大大加快了固化过程，同时也能打印出更顺滑的3D物品。这种工艺不是等待3D物品一层层地固化，而是采取了连续打印的方式，制作出来的物品可以和注塑零件媲美。 CLIP的发明者还表示，他们可以生产更精细的物品——小于20微米（和丙烯酸纤维一样厚）——而且可以使用弹性材料，以及某些生物材料。目前的大部分3D打印机都无法使用这些材料。此外，CLIP的打印过程看起来真的很炫酷——发明者甚至说，他们从电影《终结者2》中著名的液态金属机器人T-1000那里受到了启发。
但最重要的是，这种新工艺大大提升了打印速度。 CLIP的发明者说，它打印物品的速度是老式3D打印方法的25到100倍。
当3D打印速度提高100倍之后，其他3D打印厂商，FDM、SLA的会面临巨大的冲击。技术的革新可能会洗牌3d打印行业。 CLIP正在申请专利，研究人员也正在一家名为Carbon3D的初创公司中研制采用这项工艺的设备。该公司计划在今年年底前生产出CLIP打印机的商用版。目前我们尚不知道它的价格和技术规格，但我们预计，第一批Carbon3D设备的客户会是那些亟需高品质快速原型制作设备的创业公司和研究机构。总而言之，Carbon3D的钱景非常看好。
可惜，这个技术很早就被投资了4100万美元，南极熊不得不佩服风投的极为敏锐的嗅觉。现在南极熊希望和大家一起研究下这个最新技术，组建这项技术的研究和应用小组。请联系南极熊 3d@nanjixiong.com想联系这款技术的研发人员，请关注"南极熊3D"微信公众号 dddyin
下面是此项技术发明者在ted上的演讲
作者John R. Tumbleston, David Shirvanyants,Nikita Ermoshkin,Rima Janusziewicz,Ashley R. Johnson, David Kelly,Kai Chen,Robert Pinschmidt, Jason P. Rolland,Alexander Ermoshkin,* Edward T. Samulski,* Joseph M. DeSimon
摘要Additive manufacturing processes such as 3D printing use time-consuming, stepwise layer-by-layer approaches to object fabrication.We demonstrate the continuous generation of monolithic polymeric parts up to tens of centimeters in size with feature resolution below 100 micrometers. Continuous liquid interface production is achieved with an oxygen-permeable window below the ultraviolet image projection plane, which creates a “dead zone” (persistent liquid interface) where photopolymerization is inhibited between the window and the polymerizing part.We delineate critical control parameters and show that complex solid parts can be drawn out of the resin at rates of hundreds of millimeters per hour. These print speeds allow parts to be produced in minutes instead of hours.
正文Additive manufacturing has become a useful technique in a wide variety of applications,including do-it-yourself 3D printing(1, 2), tissue engineering (3–5), materials
for energy (6, 7), chemistry reactionware(8), molecular visualization (9, 10), microfluidics(11), and low-density, high-strength materials(12–15). Current additive manufacturing methods such as fused deposition modeling,selective laser sintering, and stereolithography(2, 16) are inordinately slow because they rely on layer-by-layer printing processes. A macroscopic object several centimeters in height can take hours to construct. For additive manufacturing to be viable in mass production, print speeds must increase by at least an order of magnitude while maintaining excellent part accuracy. Although oxygen inhibition of free radical polymerization is a widely encountered obstacle to photopolymerizing UV-curable resins in air, we show how controlled oxygen inhibition can be used to enable simpler and faster stereolithography.
Typically, oxygen inhibition leads to incomplete cure and surface tackiness when photopolymerization is conducted in air (17, 18). Oxygen can either quench the photoexcited photoinitiator or create peroxides by combining with the free radical from the photocleaved photoinitiator (fig. S1). If these oxygen inhibition pathways can be avoided, efficient initiation and propagation of polymer chains will result. When stereolithography is conducted above an oxygen-permeable build window, continuous liquid interface production (CLIP) is enabled by creating an oxygen-containing “dead zone,” a thin uncured liquid layer between the window and the cured part surface. We show that dead zone thicknesses on the order of tens of micrometers are maintained by judicious selection of control parameters (e.g., photon flux and resin optical and curing properties). Simple relationships describe the dead zone thickness and resin curing process, and, in turn, result in a straightforward
relationship between print speed and part resolution. We demonstrate that CLIP can be applied to a range of part sizes from undercut micropaddles with stem diameters of 50 mm to complex handheld objects greater than 25 cm in size.
Figure 1A illustrates the simple architectureand operation of a 3D printer that takes advantage of an oxygen-inhibited dead zone. CLIP proceeds via projecting a continuous sequence of UV images (generated by a digital light-processing imaging unit) through an oxygen-permeable, UVtransparent window below a liquid resin bath.
The dead zone created above the window maintains a liquid interface below the advancing part. Above the dead zone, the curing part is continuously drawn out of the resin bath, thereby creating suction forces that constantly renew reactive liquid resin. This nonstop process is fundamentally different from traditional bottom-up
stereolithography printers, where UV exposure,resin renewal, and part movement must be conducted in separate and discrete steps (fig. S2).
Even for inverted top-down approaches in whichphotopolymerization occurs at an air-resin interface[i.e., the part is successively lowered into a resin bath during printing (16, 19)], these steps must be conducted sequentially for the formation of each layer. Because each step takes several seconds to implement for each layer, and because each layer of a part has a typical thickness of 50 to 100 mm, vertical print speeds are restricted to a few millimeters per hour (16). By contrast, the
print speed for CLIP is limited by resin cure rates and viscosity (discussed below), not by stepwise layer formation. For example, the gyroid and argyle structures shown in Fig. 1B were printed at 500 mm/hour, reaching a height of ~5 cm in less than 10 min (movies S1 and S2). An additional benefit of a continual process is that the choice of 3D model slicing thickness, which affects part resolution, does not influence print speed, as shown in the ramp test patterns in Fig. 1C. Because
CLIP is continuous, the refresh rate of projected images can be increased without altering print speed, ultimately allowing for smooth 3D objects with no model slicing artifacts.
Establishing an oxygen-inhibited dead zone is fundamental to the CLIP process. CLIP uses an amorphous fluoropolymer window (Teflon AF 2400) with excellent oxygen permeability (1000 barrers; 1 barrer = 10–10 cm3(STP) cm cm–2 s–1 cmHg–1) (20), UV transparency, and chemical inertness. Dead zone thickness measurements using a differential thickness technique (fig. S3) demonstrate the importance of both oxygen supply and oxygen permeability of the window in establishing the dead zone. Figure 2 shows that the dead zone thickness when pure oxygen is used below the window is about twice the thickness when air is used, with the dead zone becoming thinner as the incident photon flux increases (see below). When nitrogen is used below the window, the dead zone vanishes. A dead zone also does not form when Teflon AF 2400 is replaced by a material with very poor oxygen permeability, such as glass or polyethylene, even if oxygen is present below the window. Without a suitable dead zone, continuous part production is not possible. For the case of ambient air below the window,Fig. 3A shows the dependence of dead zone thickness on incident photon flux (F0), photoinitiator
革命性技术CLIP让3d打印速度提高100倍，获得4100美金投资，上《science》封面
革命性技术CLIP让3d打印速度提高100倍，获得4100美金投资，上《science》封面
Fig. 1. CLIP enables fast print speeds and layerless part construction. (A) Schematic of CLIP printer where the part (gyroid) is produced continuously by simultaneously elevating the build support plate while changing the 2D cross-sectional UV images from the imaging unit. The oxygen-permeable window creates a dead zone (persistent liquid interface) between the elevating part and the window. (B) Resulting parts via CLIP, a gyroid (left) and an argyle (right), were elevated at print speeds of 500 mm/ hour (movies S1 and S2). (C) Ramp test patterns produced at the same print speed regardless of 3D model slicing thickness (100 mm, 25 mm, and 1 mm).
where F0 is the number of incident photons at the image plane per area per time, aPI is the product of photoinitiator concentration and the wavelength-dependent absorptivity, Dc0 quantifies the resin reactivity of a monomer-photoinitiator combination (fig. S4), and C is a proportionality constant. This relationship is similar to the one that describes photopolymerizable particle formation in microfluidic devices that use oxygenpermeable channel walls (21, 22). The dead zone thickness behaves as follows: Increasing either F0 or aPI increases the concentration of free radicals in the resin (fig. S1) and decreases the initial oxygen concentration by reaction. Additional oxygen diffuses through the window and into the resin but decays with distance from the window, so that free radicals will overpower inhibiting
oxygen at some distance from the window. At the threshold distance where all oxygen is consumed and free radicals still exist, polymerization will begin. Increasing the reactivity of the resin (i.e., decreasing Dc0) causes the polymerization threshold distance from the window to also shrink, thus making the dead zone thinner. The
proportionality constant C in Eq. 1 has a value of ~30 for our case of 100-mm-thick Teflon AF 2400 with air below the window, and has units of the square root of diffusivity. The flux of oxygen through the window is also important in maintaining a stable dead zone over time, which is commonly described in terms of the ratio of film permeability to film thickness (23). Using these relationships enables careful control of the dead zone, which provides a critical resin renewal layer between the window and the advancing part.
Figure 3B shows cured thickness for three different resins with varying a (holding aPI constant) where thicknesses were measured for different UV photon dosages (products of F0 and t) (fig. S3). These curves are akin to the so-called “working curves” used in stereolithography resin characterization (16, 19). For these resins, a is varied by adjusting the concentration of an absorbing dye or pigment that passively absorbs light (i.e.,
The value of hA, in conjunction with the model slicing thickness (Fig. 1C), projected pixel size, and image quality, determines the part resolution. The projected pixel size (typically between 10 and 100 mm) and image quality are functions of the imaging setup and determine lateral part resolution. As with slicing thickness, hA affects vertical resolution but is a property of the resin. If hA is high, then previously cured 2D patterns will continue to be exposed, causing unintentional overcuring
and “print-through,” which in turn results in defects for undercut and overhang geometries.
Fig. 4. A variety of parts can be fabricated using CLIP. (A) Micropaddles with stems 50 mm in diameter. (B) Eiffel Tower model, 10 cm tall. (C) A shoe cleat >20 cm in length. Even in large parts, fine detail is achieved, as shown in the inset of (B) where features <1 mm in size are obtained. The micropaddles were printed at 25 mm/hour;the Eiffel Tower model and shoe cleat were printed at 100 mm/hour.
This analysis shows that for a dead zone thickness of 20 mm, speeds in excess of 300 mm/hour with hA = 100 mm are accessible. By increasing hA to 300 mm and sacrificing resolution, speeds greater than 1000 mm/hour are readily achieved. The trade off between speed and resolution is demonstrated in Fig. 3D with resolution test patterns using the resins with different hA from Fig. 3B (all have equivalent F0aPI/Dc0 and dead zone thickness). As dye loading is increased, hA is reduced, leading to less print-through and ultimately higher resolution. However, dye absorption does not produce free radicals, so resins with lower hA require greater dosages to adequately solidify; that is, parts must be elevated more slowly for constant photon flux. On the other hand, the resin without dye and with the highest hA can be printed at the greatest speed but with poor resolution (as shown by unintentional curing of the overhangs in the test pattern). Using this process control framework, Fig. 4 shows an array of expediently produced parts ranging in size from undercut micropaddles with stem diameters of 50 mm (Fig. 4A) to full-size shoe cleats 25 cm in length (Fig. 4C). The Eiffel Tower model in Fig. 4B illustrates that fine detail is achieved even in macroscale parts: The horizontal railing posts (diameter <500 mm) are resolved on this 10-cm-tall model. This ratio of scales (1:200) confirms that the CLIP process enables rapid production of arbitrary microscopic features over parts having macroscopic dimensions. For these parts, the speed-limiting process is resin curing (Eq. 4); however, for other part geometries, the speed-limiting process is resin flow into the build area. For such geometries with comparatively wide solid cross sections, parameters that affect
resin flow (e.g., resin viscosity, suction pressure gradient) become important to optimize. Preliminary studies show that the CLIP process is compatible with producing parts from soft elastic materials (24, 25), ceramics (26), and biological materials (27, 28). CLIP has the potential to extend the utility of additive manufacturing to many areas of science and technology, and to lower the manufacturing costs of complex polymer-based objects.
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