Jan 14, 2019 | By Thomas

Researchers from the University of Michigan have developed a new approach which can 3D print lifts complex shapes from a vat of liquid at up to 100 times faster than conventional 3D printing processes.

In a paper published in the journal Science Advances, researchers outlining the principles of using light to shape resins in a vat of liquid. The breakthrough promises faster and more efficient small-scale manufacturing by enabling goods to be produced in one quick go.

Traditional 3D printing methods create 3D objects with a series of one dimensional lines. The technique means that the objects could be made without the need for a mold costing upwards of $10,000. However the process is still slower and hasn't been able to fill the gap on typical production timescales of a week or two.

"Using conventional approaches, that's not really attainable unless you have hundreds of machines," said Timothy Scott, U-M associate professor of chemical engineering who co-led the development of the new 3D printing approach with Mark Burns, the T.C. Chang Professor of Engineering at U-M.

Credit: Science Advances

Their method solidifies the liquid resin using two lights to control where the resin hardens and where it stays fluid. This enables the team to solidify the resin in more sophisticated patterns. They can make a 3D bas-relief in a single shot rather than in a series of 1D lines or 2D cross-sections. Their printing demonstrations include a lattice, a toy boat and a block M.

"It's one of the first true 3D printers ever made," said Burns, professor of chemical engineering and biomedical engineering.

Previous attempts to solidify objects in a vat of liquid faced limitations because the resin tends to solidify on the window that the light shines through, stopping the print job just as it gets started.

By creating a relatively large region where no solidification occurs, thicker resins -- potentially with strengthening powder additives -- can be used to produce more durable objects. The method also bests the structural integrity of filament 3D printing, as those objects have weak points at the interfaces between layers.

"You can get much tougher, much more wear-resistant materials," profressor Scott said.

An earlier solution to the solidification-on-window problem was a window that lets oxygen through. The oxygen penetrates into the resin and halts the solidification near the window, leaving a film of fluid that will allow the newly printed surface to be pulled away.

But because this gap is only about as thick as a piece of transparent tape, the resin must be very runny to flow fast enough into the tiny gap between the newly solidified object and the window as the part is pulled up. This has limited vat printing to small, customized products that will be treated relatively gently, such as dental devices and shoe insoles.

By replacing the oxygen with a second light to halt solidification, the Michigan team can produce a much larger gap between the object and the window -- millimeters thick -- allowing resin to flow in thousands of times faster.

Credit: Science Advances

The key to success is the chemistry of the resin. In conventional systems, there is only one reaction. A photoactivator hardens the resin wherever light shines. In the Michigan system, there is also a photoinhibitor, which responds to a different wavelength of light.

Rather than merely controlling solidification in a 2D plane, as current vat-printing techniques do, the Michigan team can pattern the two kinds of light to harden the resin at essentially any 3D place near the illumination window.

U-M has filed three patent applications to protect the multiple inventive aspects of the approach, and Scott is preparing to launch a startup company.

 

 

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Boaty McBoatface wrote at 1/26/2019 2:31:32 AM:

Glass micro beads can be a transparent filler to add strength. Parts can be painted or dyed after printing to add color.

The Power wrote at 1/14/2019 7:29:43 PM:

Very cool tech but this will have to be limited to relatively transparent resins that allow the light to penetrate "a couple millimeters" into the material to be feasible. I am not so sure that you could implement this with "powders" and other strengthening media added to the resin as discussed earlier in this article.



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