One of the “dirty secrets” of 3D printing is the universal need to take additional steps to render the output usable, including removing the part from its support, curing the part, or improving the surface. Aside from additional cycle time and cost, these steps often require or emit toxic chemicals, necessitating special ventilation and making them unsuitable for a standard office environment. For example, parts built with fused deposition modeling (FDM) must spend about four to eight hours in a heated, agitated sodium hydroxide bath.
Rize’s patented augmented polymer deposition (APD) process extrudes a proprietary thermoplastic while simultaneously jetting functional inks at each voxel. One such ink allows the part to separate easily from the support structure, leaving a clean surface and eliminating the need for post-processing. Plus the parts are fully isotropic, rivaling injection molding quality, according to Rize.
Another limitation of many 3D printing technologies is the relative weakness of the bonds between the layers, creating part weakness in the Z-axis (the direction in which the layers are deposited). So while an injection molded part might be nearly 100% isotropic (equally strong in all directions), typical FDM parts lose around 40% of their Z-strength.
A new 3D printer manufacturer based in Woburn, MA, has technology that appears to virtually eliminate both problems. Founded by industry veteran Eugene Giller (and soon joined by Leonid Raiz, Tom Davidson and others), Rize Inc. offers a patented process it calls Augmented Polymer Deposition (APD). In APD, an extruder deposits Rize’s own “engineering- and medical-grade thermoplastic” (Rizium One) as a print head simultaneously jets special additives (also called “inks”) at each voxel (3D pixel). After building a thermoplastic support for the part, the print head jets a layer of proprietary Release One ink as the extruder builds the first layer of the part. This special ink weakens the molecular bond between the part and the support, making it easy to remove the completed part from the support by hand, with no additional post processing. Julie Reece, vice president of marketing and channel relations, said “even the surface where the support had been is clean and smooth.”
What’s more, Rizium One is similar to polycarbonate and much stronger than acrylonitrile butadiene styrene (ABS), boasting twice the strength of ABSPlus in the Z-axis. This has been borne out in testing by one of Rize’s prospective customers, who performed a functional strength test in which the APD printed part rivaled the same part in machined nylon. The APD technique also has the ability to jet marking inks at each voxel, enabling the addition of high resolution monochromatic graphics on any surface during the build.
The Rize One 3D printer was introduced at SolidWorks World in February 2017 and is now in production. With a 12 × 8 × 6 inch (300 × 200 × 150 mm) build envelope, 0.25 mm resolution, and a base price of $28,500, it can be used to make fully functional prototypes or customized one-off production parts in an office environment, without post-processing. Reece added that “our machine’s annual operating cost is about $10,000, versus the $90,000 you’d experience with comparable FDM systems. And you’d spend $120,000 to $150,000 up front with those systems to get similar capabilities.”
The engineers at Rize are looking toward the ability to print photo-realistic color on the next release. Even more intriguing, they envision the ability to include other functional materials in a build, such as conductive, thermo-insulating, and thermo-conducting inks. This could, for example, enable the creation of a battery within a 3D printed structure. And because the APD approach enables the modification of the mechanical properties of the plastic as it’s being printed, Rize is working on a solution that would produce a hearing aid with a soft and flexible outer layer for comfort, combined with rigid interior channels for optimum sound.