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3-D Printing Quality on the Upswing
3D Systems' newest 3-D printer systems occupy middle ground between low-cost concept modelers and high-end additive fabrication machines
Joseph Ogando, Senior Editor -- Design News, August 22, 2008
It's tempting sometimes to put additive fabrication machines into just two buckets. One of them has high-end, six-figure systems capable of producing precision prototypes and even finished components in rugged materials. The other contains 3-D printers, a growing class of lower-cost systems that engineers often use for concept and testing models. Yet 3-D printer capabilities vary so widely that perhaps they shouldn't be lumped together.
Consider, for example, the newest line of ProJet machines from 3D Systems Corp. The company's senior director of global marketing, Buddy Byrum, argues these machines fit into an emerging class of "professional modelers." The surface finish, accuracy, feature resolution and throughput of machines occupy a middle ground between the low-cost concept modelers, some of which cost less than $20,000, and high-end fabrication machines whose prices start at $100,000. "The difference between professional modelers and concept modelers is like the difference between high-def and analog television," Byrum says.
Like 3D System's earlier InVision family, the new machines employ Multi-Jet Modeling (MJM), one variant of several related 3-D printing methods that use ink jet technology to deposit the layers of build and support material.
However, a couple of things set MJM apart from other ink jet systems. For one, its acrylate polymer build material undergoes a phase change once it leaves the jets, allowing it to "set" on the model even before each build layer is cured by UV light. "The droplets freeze in place on the model," Byrum says. "And that lets us build high-quality parts with crisp features." Byrum adds freezing of the drops also permits relatively thick build layers without a loss of part quality. "That gives us high throughput capacity for a given build volume," he says.
For another, the MJM is a single-pass design in that the ink jet head spans the entire y-axis. So its build speed is unaffected by the number of parts packed onto the build platform. "Build time is determined only by the how tall the parts are," Byrum says.
MJM technology is a two-material system that lays down both a build material and wax-based support material. That support material is later melted away from the model, which is important when working with delicate part features that could be broken with more aggressive methods of removing supports, such as using a blast of pressurized liquid. "We have a support removal method that doesn't put any pressure on the part," Byrum says. The result is the machine's accuracy and resolution dictate the smallest feature size rather than the feature's ability to survive a wax removal process.
3D Systems has rolled out three versions of its new ProJet platform, one specifically for the dental industry and two models better suited to design engineering work. The first of these two engineering models, the ProJet HD 3000, appeared earlier this year. This week, the company launched a brand new model, the ProJet SD 3000.
What's the difference between the two? Ten thousand dollars and a handful of features.
The $69,900 HD builds in two modes, a high-definition (HD) mode offering a 328 x 328 x 606 DPI (xyz) resolution and and an ultra-high-definition (UHD) mode offering 656 x 656 x 800 DPI. The ProJet HD 3000 has a typical accuracy of 0.001 to 0.002 inch per inch of part dimension, though Byrum stresses accuracy varies with build parameters, part geometry and size, part orientation and post-processing methods.
The z-direction build speed for the HD mode is about 0.25 in/hr, while the UHD mode builds at 0.1 in/hr, Byrum reports. The ProJet HD also has the ability to stack different parts within the z-direction. "You can pack them in any way that fits as long as the parts aren't touching," Byrum says. Build volume in the HD mode is 11.75 x 7.3 x 8 inches while the UHD mode offers 5 x 7 x 6 inches.
The $59,900 ProJet SD, meanwhile, is basically what Byrum calls an "entry-level machine for professional modeling." It lacks the UHD resolution and the ability to stack parts in the z-direction. Other than those two differences, it shares the capabilities of the ProJet HD.
Applications for the ProJet machines include the production of complex parts, especially ones that require form-fit-and-function testing. It also turns out models ready for use as investment casting patterns for intricate metal components.
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