今年年初在消费电子展上推出时，它的主要卖点是能打印两种颜色。虽然令人印象深刻，但要记住，“两种颜色”只是“黑白”的另一种说法。
理查德·霍恩是个电气工程师，也是一位3D印刷爱好者。他并不满意这种只能打印黑白颜色的限制，他甚至想要印刷出成百上千种颜色。因此，他开始了修改他的RepRap来动态生成新色调的工作。由于实在找不到比他自己更适合的名字，他为他的打印机黑客取名为“Rich Rap”。
这是它的工作原理：RichRap有三个挤塑马达，把原料注入到一个管嘴或热端，每个马达卷着塑料丝进入热端，塑料丝在那里熔化，然后堆积在生成的表面。操作人可以把红、黄、蓝色的塑料装进RichRap，然后通过混合黄色和蓝色来生成绿色，或者混合红色和蓝色来生成紫色。
公正提醒：RichRap制造出的零件，看起来更像是扎染而不像喷墨印刷输出。颜色并不是真正混合出来的，它们是用一种霍恩称为“挤牙膏作用”的方式调和，即颜色之间以一定的距离互相旋转混合起来。同时，机器有着所有已知的熔丝制造的局限性，如脊状的表面和相对低的分辨率。
使用一台专业的3D彩色打印机，比如那些由ZCorp公司制造的打印机，设计师能够指定颜色到一个像素的水平。一个设计作品可以把绿“像素”贴放在红“像素”旁边。使用RichRap，颜色效果更加渐变自然，因为塑料熔化转型需要时间。
虽然RichRap表面上可能看起来像一个简单的模块，但它的更多迹象是如何开源3D印刷术，使得桌面用户能以有趣的方式来推进这项技术。“开源的3D打印机和软件工具都发展得非常快，”霍恩说，“目前它还是个小产业，但是不久之后，将会是个巨大的市场”。
When the MakerBot Replicator was introduced at CES earlier this year, its main selling point was the ability to print in two colors. While impressive, remember “two color” is just another way of saying “black and white.”
Richard Horne, an electrical engineer and 3-D printing enthusiast, wasn’t happy with that limitation. He wanted to print in color, hundreds of them, even. So, he got to work modifying his RepRap to dynamically generate new hues. Finding a no more fitting name than his own, he dubbed his printer hack the “Rich Rap.”
Here’s how it works: The RichRap has three extruder motors feeding into one nozzle, or hot end. Each motor spools plastic filament into the hot end where it is melted, then deposited on a build surface. An operator could load a RichRap with red, yellow, and blue plastics and generate green parts by mixing the yellow and blue, or purple by mixing red and blue.
Multi-color printing makes standard parts, like brackets, canvases for expression.
Fair warning: Parts made on the RichRap look more like tie-dye than ink-jet printouts. Colors don’t really mix, they blend in a fashion Horne calls the “Toothpaste effect” where colors swirl and blend at a distance. Also, the machine has all of the known limitations of fused filament fabrication, like ridged surfaces and relatively low resolution.
With a professional color 3-D printer, like those made by ZCorp, designers have the ability to specify color down to a pixel level. A design could have a green “pixel” right next to a red “pixel.” With the RichRap, color effects are more gradual and organic, as the melted plastic takes time to transition.
While the RichRap may seem like a simple mod on the surface, it’s more evidence of how open source 3-D printing is enabling desktop users to advance the technology in interesting ways. “Open source 3-D printers and software tools are developing very quickly,” Horne says. “It’s a small industry at the moment, but it will be a massive market not long from now.”
