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An affordable, self-correcting, multi-material 3D printing platform

3D printer scans each layer and makes fixes as needed.

An affordable, self-correcting, multi-material 3D printing platform

Research on 3D printing (also called additive manufacturing) has increased the accessibility of the technology to the general public. Today you can even buy your own 3D printer, although at a steep price—the cost of these systems has hindered their wide-scale use. Recently, an interdisciplinary team at MIT’s Computer Science and Artificial Intelligence Lab (CSAIL) has partly addressed this limitation by building a relatively cheap printer that can handle multiple materials.

From the beginning, the team was interested in a 3D printing platform that relied on commercial, off-the-shelf parts. Over the past three years, they’ve developed an impressive multi-material 3D printing platform that costs around $7,000—over an order of magnitude cheaper than other multi-material systems.

The printer is 1.2m x 0.6m x 1m (w, l, h), and its frame is made of aluminum attached to UV-blocking acrylic sheets. An exhaust duct is connected to the rear of the panel where two electric fans are used to expel gases and particulates.

In addition to the price point, the scientists and engineers were able to design a system with significant improvements over existing technologies. A single CPU is in charge of all the printer subsystems, which include a positioning subsystem (with X, Y, and Z axes), a material feeding subsystem, printhead modules, and UV-curing modules.

In addition, the system has a real-time 3D scanning module, a significant new feature in this printer design that allows every layer to be scanned as it’s printed, enabling the ability to generate correction data if necessary. After correction, the average error is only 5μm.

The system relies on inkjet printer technology, with the printhead module containing five channels, each of which can house different materials. It uses piezoelectrics to dispense tiny droplets ranging in size from 6 pico-liter (pL) to 26 pL in volume. CSAIL research engineer Javier Ramos explained that “a very attractive thing about inkjet technology is that it scales very well [and] you generally have better resolution... You can get smaller droplets and actually print faster.”

The system can print several types of materials; this material library is continuously being expanded as the team develops new materials and tests materials designed for extrusion systems. Their library currently includes rigid, elastic, high refractive index, and low refractive index materials. At this point, the platform can print up to 10 different materials that can interact optically and mechanically. The biggest limit right now is its reliance on polymer materials. Ramos commented, “The eventual holy grail of 3D printing is to combine metals, polymers, and ceramics in one single platform. We are heading in that direction, but we’re not there yet.”

The platform is run using an application called Fabricator, which receives input in a multi-material voxel format and then processes the information from the bottom up in a layer-by-layer fashion. The Fabricator is able to control the material loading, droplet sequence, and size at each printhead nozzle, positioning module, and UV-curing module. The platform also uses the machine vision system, software that is run on the central computer. This software controls the 3D scanner, a 2D camera, and the other hardware.

The new 3D printing platform has been tested by fabrication of a variety of devices, including microlens arrays, optical fiber bundles, and privacy screens. It has also been used to create highly specialized materials. For example, the team demonstrated the ability to combine rigid and elastic materials with empty spaces in a way that enables the material to expand when it is stretched (an auxetic material).

Finally, the system has the unique ability to print over existing objects, which opens the application space. As an example, the developers demonstrated that they were able to print a holder surrounding a razor blade placed in the device.

This multi-material 3D printing platform was presented earlier this month at the SIGGRAPH computer-graphics conference.

Channel Ars Technica