Two features of 3D printers that can be issues for users are the surface finish quality of the part and the subsequent post processing often needed to finish the part.
The developers at Rize created a 3D printer to address these issues. The Rize One 3D printer is small enough to sit on a desktop, but has a build size of 12 x 8 x 6 in. (300 x 200 x 150 mm). According to Frank Marangell, president and CEO of Rize Inc., this printer is a suitable alternative for injection molding applications, including medical, spare parts, and industrial tooling. The printer prints in 250-micron layers with a finish comparable to injection molding. One limitation is if very fine detail is required; then injection molding may be the better choice.
The printer is able to deliver comparable injection molding finish through the use of two techniques for material deposition, extrusion and jetting. These two techniques deposit three different materials. An extruder head deposits an engineered thermoplastic, known as Rizium One, on the build plate. Then, a repelling ink, Release One, is deposited on top of that. This release material makes it easy to remove a part from the build plate.
Next, additional layers of the thermoplastic are deposited. Depending on the part, users will be able to jet any of six different specialty inks between the thermoplastic layers to create patterns of color or words. In the next generation of the Rize One, users will be able to jet CMYK color. A final material is jetted over the entire build which results in a near injection molded type smooth surface finish.
This whole process is referred to as Augmented Polymer Deposition (APD), developed by materials scientist Eugene Giller, Co-Founder and CTO of Rize. The combination of deposition methods gives users near voxel by voxel control. Plus, it eliminates much of the post processing. Since about 80% of the 3D printing market involves the use of plastic material, anything that reduces or eliminates post-processing time and cost is beneficial.
The engineered thermoplastic material is medical grade with a high Z strength of about 70 megapascals. According to the company, the material looses less than 10% of its strength in the Z direction in the APD process, which makes the material near isotropic in strength.
The mechanical properties of Rizium One include being water tight, and non-water absorbent with swelling and expansion of less than 1%. The material can be used for form, fit, and function.
All of these material features and the 3D printer itself combine to deliver parts that need little post processing. According to a recent paper written by Todd Grimm of T.A. Grimm & Assoc., “3D Printing: The Impact of Post Processing,” post processing is a factor inhibiting the widespread use of 3D printing.
Post processing can include support removal, sanding, filling, priming and painting, and machining and plating. These processes often improve the aesthetics of a 3D printed build, and can improve the function of the part. But if not properly accounted for, it can also add hours or days to the total print build, as well as cost to the final 3D printed part.
In addition to equipment needed to post process, Grimm estimates the direct labor cost of post processing being roughly $25,000 to $50,000 per year for each 3D printer.
Several recent reports indicate many 3D printing plastics require special installation because they emit toxic fumes. “The fumes and the need to be near post processing operations are some of the factors locking 3D printers into labs today,” noted Marangell. Rize hopes to break 3D printers out of labs and give engineers a professional desktop tool with minimal post-processing needs.
Leslie Langnau
llangnau@wtwhmedia.com
