Machine Design

Now it's easy being GREEN... or RED ... or BLUE ...

3D printing has been around for a decade but vendors continue to push the technology envelope.

Full-color 3D modeling with inkjet technology makes rapid prototyping more efficient.

Thomas Clay
Z Corp.
Burlington, Mass.

The color version of this compressor model clearly shows additional detail.

This model of a tennis-shoe sole was produced on a color 3D printer.

A company selling soft drinks designs and prints various versions of can labels directly onto the model of the can, with enough detail to read the ingredient list or see the bar code. With this level of detail, decisions can be made without resorting to more costly and time-consuming alternatives.

No one would produce a CAD drawing without some form of engineering label to provide information. The same goes for a 3D model. The engineering label on this model casing shows the name of the part, scale, printing date, and designer's name.

This model of a transmission housing highlights machining steps.

This 3D model of a turbine blade shows the results of FEA.

As a result, capabilities once the domain of RP (rapid-prototyping) equipment costing several hundred thousand dollars now appear in 3D printers costing $25,000 to $50,000.

One recent development is full-color printing, based on inkjet technology, of 3D models. Multi-color inkjet printers use a powder-binder technology patented by the Massachusetts Institute of Technology. These third-generation color printers run on software specifically designed to exploit the potential of color.

Printing models in color improves communication in the design process and gives users a better idea of how a final product will look. Few would argue that a monochrome part conveys as much information about its complexity as a multicolor version. Some of the potential applications for color 3D printing are concept modeling, communication, and analysis.

For years, 3D printers have been producing monochrome concept models for use in the early stages of the design process, where most iterations take place. But many products, especially consumer products, use multiple colors and labels to catch the eye. It is vital to capture these design elements as they can account for a large portion of a product's final appearance.

In the past, companies resorted to painting models, a tedious and time-consuming process. To view packaging and labels, with their more complex use of color, companies typically relied on computer renderings.

Some monochrome 3D printers can produce materials in different colors or make multicolor models. But the process can be cumbersome. The operator must print each component of the model in a different color and then assemble the components. For some time, 3D printers using inkjet technology have printed a full range of colors in a manner similar to 2D color printers, but the technology failed to provide color crispness and good detail. Consequently, full-color 3D printing gained acceptance in some industries, but color fidelity did not meet the standards in others — especially in consumer goods.

A new generation of color 3D printers using inkjet technology released earlier this year overcame the problem by reaching new levels in color quality. Early signs suggest that the imaginary barrier for 3D color printing has been broken.

For example, designers at Fisher Price, one of the world's leading toy manufacturers, were able to release three product concepts directly to manufacturing in the first month of switching to a color 3D printer. The decisions were based on viewing 3D models that were printed, rather than painted, in color — a first for the company.

The color produced by a 3D printer is fundamentally different from that of a regular paper printer. In 2D printers, a monochrome device can put black words on white paper. In 3D printing, a comparable operation requires a color printer because the output of a monochrome 3D printer is a monochrome object, usually white. 3D color printing opens a new range of applications, even for users who do not need full-color parts.

Another advantage of color is its ability to convey information about manufacturing steps when a design is complete and needs to be transferred to manufacturing (or a supplier). Take, for example, a transmission housing. Once the part has been cast, several additional manufacturing steps are required. By using color, it is easy to highlight surfaces that must be machined, holes that must be drilled, and so forth.

An even simpler use of color is to identify the order in which a complex assembly is done, for example, blue first, red second, and yellow last. Other communication applications include highlighted edges on a part for emphasis or additional treatment, such as deburring. Designers can get creative and add visual effects, like shadows, to enhance communication. Possibilities are only limited by the imagination.

Data analysis is another area where color offers tremendous value. Sometimes it is not possible to properly visualize the output of an FEA analysis merely by looking at data on a screen. For example, thermal, stress/strain, and geological analyses applied to 3D models offer a visual representation that makes it easy to spot problem areas.

But to fully exploit color's potential, it must be easy to produce the data files to be printed. A number of file formats (VRML, PLY, and others) support color. In some cases, texture maps and most CAD tools can export these files. STL exports are more prevalent and tend to be of better quality, but the format does not support color.

Another enhancement in 3D color printing is in the software. Zedit software, which is made by Z Corp., lets the user color whole parts or a bounded region such as a face; place a texture map on the part (jpg, bmp); annotate or "mark-up" a part with circles, arrows, and text; or place engineering labels on a part.

Once the file has been prepared, a process that is mostly automatic, the task of enhancing the part with color is straightforward. For instance, a user could wrap a label around a bottle and then shape it to fit in a few mouse clicks.

3D printers should function like 2D printers in that users expect them to be fast, economical, and easy to use. For their part, manufacturers are moving toward a "one-click" solution for transforming color 3D data from any source into a physical model. Our world is inherently one of color and color 3D printing responds to that reality.

Z Corp.,

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