A novel 3D printing technique suspends light-curing resin in a gelatinous medium rather than using conventional structural support material during the build process. The gel acts as an omnidirectional support material and is reusable.

The technique is the brainchild of Brian Harms, who is still pursuing a Masters in Design Research at the Southern Calif. Institute of Architecture (SCI-Arc). The suspended deposition method he devised has yet to be commercialized, though that could happen in the future.

The suspended deposition prototype uses a Scara robot arm with a pump and extruding nozzle on its end effector. Once the material gets deposited in the gel, it is exposed to UV for curing. One interesting facet of this method is that the build material can be 'erased' any time before it cures simply by sucking it back into the nozzle. Another point to note is that material can deposit in 3D vector-based toolpaths. This contrasts with virtually all other 3D printing processes where successive layers must harden before the machine can move on to the next.

The fact that the resin sits in space without support material also makes it possible to fabricate directly on and around other objects sitting in the Gel. And the build material can sit in the gel waiting while the robot arm makes a tool change, injects a different material, or implements other changes that require a pause in the action.

Harms says he's just applied for a provisional patent covering the basic functions of the system in the context of rapid prototyping. "There may very well be patents on file that cover some of the aspects of the system," he says, "but in case there aren't, I decided it would be prudent to at least get a filing date." 

Harms also calls the suspended deposition technique "purely an experimental endeavor" at the moment. He adds that he'd like to continue researching the idea but has no specific time frame in mind for commercialization. "There's a lot of work that would need to be done to make this process robust enough to become part of the 3D-printing market, and much of that would rely on funding," he says. "But we do have several ideas for improving the process both in terms of it's interface and physical set up. One of the most pressing issues would be the design of needle-tip attachments or articulated needle tips. This would help mitigate one of the major problems we face, which is the tendency for the resin to travel up alongside the needle as it passes through the gel, leaving a temporary void."

Accuracy and resolution is another issue. "Our needle is rather large and has an interior diameter a little larger than 1/16 inch. We haven't experimented much with any other sizes, but we think there is a lot of potential there," Harms says. "We are dealing with a liquid as opposed to a filament (which has a very consistent diameter) so we could actually actuate the needle opening, potentially allowing us to vary the resolution throughout the print."

Harms says the impetus for the project arose out of pondering how a robot would handle 3D printing. "The answer for us was articulation. A six-axis robot gives us possibilities for motion that the three-axis machines can't," he says.Harms' first pump was a dual-nozzle, dual-centrifugal design created with the idea of handling multi-material injections simultaneously --  perhaps dispensing two-part resins that would only cure in the gel once the two parts had come in contact with one another. The idea  didn't work well because the pumps put out too much material, even at their slowest settings. He ended up building his own peristaltic pump that is integrated into the tool.

Harms says the first items fabricated on the machine were a series of wireframe cubes chosen because they gave developers an idea of how changes in process parameters affected build quality. "For example, if we kept the flow rate constant but changed the speed of the robot, we would see the resin thin out as the robot sped up. So we used those objects as a way to calibrate the system," Harms says.

"We also created a series of spheres to show that while each was  identical geometrically, it could be generated using very different toolpaths (which this system affords). One was built using vertical as opposed to horizontal contours, one was made using vertical radial arcs, and one was done in a continuous spiral," Harms says.

"We also printed a ring of resin that interlocked with a plastic ring that we had previously submerged in the gel. This was our sort of proof of concept for multi-material/multi-object operations," he relates.

Harms says the suspended deposition method will probably be limited to resins for the foreseeable future. "I think metals would be really tricky just given the temperature ranges you would have to deal with," he says. "I suppose if you were working with metals with really low melting points and you had a substrate that was incredibly insulative, you might be able to work that out. But that's just speculation at this point."

3D打印新方式：悬浮物体凝固

一种新颖的3D印刷技术暂停光固化树脂胶状介质，而不是在构建过程中使用传统的结构支撑材料。凝胶充当一个全向载体材料并且是可重复使用的。

该技术是布赖恩·哈姆斯，谁仍然在奉行一个大师设计研究在建筑的南加州学院（SCI弧）的心血结晶。他设计的悬浮沉积方法尚未实现商业化，通过这可能在未来发生。

悬浮沉积原型使用的SCARA机械手臂，在其末端执行泵和喷嘴挤出。一旦材料被沉积在凝胶，其暴露于紫外线进行固化。这种方法的一个有趣的方面是，该构建材料可以是'擦除'任何时间通过抽吸它放回喷嘴固化简单地之前。还有一点要注意的是，材料可以在3D基于矢量的刀具路径押金。与此相反，几乎所有的其它三维印刷方法，其中的连续的层，必须硬化之前的机器可以在移动到下一个。

该树脂在没有支撑材料的空间坐的事实还使得能够制造上直接与周围的其他对象坐在凝胶。和制作材料所用的凝胶等待坐而机器人臂使换刀，喷射不同的材料，或实现该要求在动作暂停其他变化。

哈姆斯说，他只是申请了临时专利涵盖快速成型的背景下，系统的基本功能。 “有很可能覆盖一些系统的各方面的专利文件，”他说，“但万一有没有，我决定这将是审慎的做法至少可以得到一个申请日。”

危害也要求此刻的悬浮沉积技术“纯粹的实验努力”。他补充说，他想继续研究这个主意，但具有商业头脑中没有具体的时间框架。 “还有很多需要做才能使这个过程足够强大，成为3D打印市场的一部分，而且大部分将依赖于资金的工作，”他说。 “但我们确实有一些想法改善的过程无论在它方面的接口和物理的设置。其中最紧迫的问题是针尖附件或铰接针尖的设计。这将有助于减轻主要原因之一我们所面临的问题，这是因为该树脂在旅游向上沿着针，因为它通过凝胶，留下一个临时空隙的倾向“。

精度和分辨率是另一个问题。 “我们的针是相当大，有一个内部直径小于1/16英寸的大了一点。我们没有太多尝试与其他任何尺寸，但我们认为还有很大的潜力在那里，”哈姆斯说。 “我们正在处理的，而不是一个灯丝（其中有一个非常一致的直径）的液体，所以我们实际上可以促动针口，有可能使我们能够改变整个打印分辨率。”

哈姆斯说，推动项目产生于思考如何机器人将处理3D打印的。 “对我们来说，答案是衔接。六轴机器人为我们提供了可能性运动的三轴机器不能，”他说。危害“第一泵是具有同时处理多材料注射的想法创建一个双喷嘴，双离心设计 - 也许分配两部分组成的树脂，将只治愈在凝胶一旦两个部分已经到来在接触与一种另一回事。这个想法并没有很好地工作，因为泵拿出太多的材料，即使在最慢的设置。他结束了自己造的蠕动泵集成到工具。

哈姆斯说，制造机器上的第一个项目是一系列的选择，因为他们给了开发人员的变化，工艺参数如何影响建设质量的想法线框立方体。 “举个例子，如果我们保持流速不变，但改变机器人的速度，我们将看到树脂薄膜作为出机器人加快。因此，我们使用的对象，以此来校准系统，”哈姆斯说。

“我们还创建了一系列的球体显示利用非常不同的刀具路径（该系统能提供哪些）。使用垂直而非水平轮廓的一建，虽然每个是相同的几何，它可以产生，一个被利用垂直径向弧线取得，一个是在连续的螺旋形做，“哈姆斯说。

“我们也印刷的树脂的环，与我们在凝胶以前淹没塑料环互锁。这是我们这类概念的多材料/多对象操作的证据，”他涉及。

危害说悬浮沉积方法可能会被限制为树脂，在可预见的未来。 “我认为刚才的温度范围内，你将不得不处理的金属将是非常棘手的，”他说。 “我想，如果你正与金属与真正的低熔点和你有一个底，这是令人难以置信的绝缘，你也许可以工作了这一点。但是，这仅仅是猜测在这一点上。”