3D printing color

http://mashable.com/2015/06/19/3d-printing-color/

3d-prints

3D printing has been taken to a whole new level: Color

3D printing is driving a huge revolution in the world of design and technology. In the process, it is changing the way we think about the design, prototyping and manufacturing of just about everything.

But anyone who has played with a 3D printer will be aware of one significant problem. This 800-pound gorilla is the issue of color. 3D prints can be magnificent copies of more or less any shape. But in terms of color, they are mere shadows of the originals.

Today, that looks set to change thanks to the work of Alan Brunton and pals at the Fraunhofer Institute for Computer Graphics Research in Germany, who have worked out how to produce accurate colors in a 3D print for the first time. Their work promises to take 3D printing to an entirely new level.

The approach takes advantage of a relatively new way to make 3D prints. In general, these objects are made one layer at a time by fusing powder or laying down extruded plastic. Neither approach gives anything but rudimentary control over an object’s color.

What’s needed instead is a way of creating objects in the same way as 2D printers make images, pixel by pixel. In other words, this requires 3D prints to be laid down, not in layers, but voxel by voxel.

In the last year or so, exactly this technology has come to market. It works using a number of inkjets that lay down an object, droplet by droplet. These droplets are instantly cured by UV light to form a solid.

That immediately allows the possibility of much more accurate control of color, since each droplet can be thought of as a voxel. This is the approach that Brunton and pals have taken, but it is easier said than done for a number of reasons.

The first is the sheer volume of data and number crunching involved in creating a virtual color 3D object, even before the printing begins.

The droplets from inkjets are tiny — there are some 18 million of them in a solid cubic centimeter. So any decent-sized object must be made up of tens of billions of voxels and the impact that each one has on the final color has to be calculated.

The second is that the droplets are translucent because UV light must be able to pass through to cure them. This has a significant impact on their visual appearance since light ends up passing through several layers of voxels, being scattered along the way.

That means droplet color has to be carefully controlled to a depth of several voxels throughout the object. And this dramatically increases the complexity of the algorithms needed to calculate their required colors.

The final challenge comes from the nature of 3D printing. In 2D printing, it is possible to combine up to three different inks at any point on an image. In a 3D print, each droplet must be a single material and that places important constraints on what is possible colorwise.

Nevertheless, Brunto and co have made significant advances by bringing to bear the many decades of research that has been done on color management for 2D printing and for color imaging in general.

Their approach is to combine two techniques. The first is the 3D equivalent of a 2D printing technique called half-toning. This is where continuous shade and color is replaced by an arrangement of dots of different sizes and spacing. The second is a way of calculating the color of a surface given the way light has been scattered for several layers of voxels below.

And the results look impressive. In the pictures above, three apples and the thumb are real. The rest are 3D prints but it is not easy task to tell them apart.

And Brunton and co say the results should get better in the near future as materials scientists develop less translucent printing materials and as printers become even higher resolution. In both these respects, the team’s algorithms are future proof. Less translucent inks should be easier to handle and the higher resolution should be manageable too.

The ability to combine translucent and opaque inks should even make it possible to reproduce the surface appearance of many biological materials that are also semi-translucent, such as skin.

That’s fascinating work. It will usher in a new generation of printing application. And it will make the current generation of printers look thoroughly old-fashioned in just a few years.

References:

mashable.com

http://mashable.com/2015/06/19/3d-printing-color/

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New face for a girl thanks of 3D printing

http://www.cbc.ca/news/health/3d-printing-helps-give-girl-a-new-face-1.3014957

Violet Pietrok, playing with her father Matt, was born two years ago with a Tessier cleft, a rare deformity in which the bones that form the face have not fused properly. Thanks to 3D printing of models of her skull, Violet has begun a series of surgeries to correct the problem.

3D printing helps give girl a new face

Doctors practise on an exact image of face before repairing deformity.

The great thing about medical school cadavers is that they can’t die.

If a surgeon in training makes a mistake, there’s always next time. It is the last environment where medical errors have no consequences.

But 3D printing is changing that, giving even experienced operating room teams valuable practice on a model that looks and feels like the real thing. It has life-saving and life-altering implications.

Violet Pietrok was born two years ago with a rare deformity called a Tessier cleft. The bones that normally join to form the fetal face had not fused properly.

  • Watch David Common’s full story on The National Sunday April 5 at 9 p.m.

As a result, Violet’s eyes were set so far apart, her vision was more like a bird’s than a human’s. She also had no cartilage in her nose.

But the corrective operation is extraordinarily complex. So Violet’s family turned to one of the world’s leading reconstructive surgeons, Dr. John Meara, at Boston Children’s Hospital.

Violet Pietrok

He warned them of the danger of making sophisticated cuts through the skull, very close to the optic nerve. “They might be very close to the brain,” Meara explained in an interview. “So the ability to make these cuts on the model first and see the trajectory of a sawblade or where that cut would come through in relationship to the eye is absolutely critical.”

To get that model, the simulation team at Boston Children’s took multiple MRIs of Violet’s skull and replicated it on a 3D printer.

It took more than a day to print, but the model is exact. Even the density of the bone is precise.

 “We were actually able to do the procedure before going into the operating room,” Meara said.

“So we made the cuts in the model, made the bony movements that we would be making in Violet’s case and we identified some issues that we modified prior to going into the operating room, which saves time and means that you’re not making some of these critical decisions in the operating room.”

During the surgery earlier this year, Meara kept a model of Violet’s skull close by and referred to it as he went through the complicated steps of the operation. This successful surgery was just the first of several that will be needed to remake Violet’s face.

Other hospitals are interested

Boston’s success has prompted a lot of calls from hospitals around the world looking to set up their own 3D printing simulations to Dr. PeterWeinstock, who runs the Boston program.

He equates medicine with sports teams. Any team worth its salt, he says, practises before the game.

“We looked at that and thought, why is health care not doing that?  If you can see the patient before you see the patient, if you can do the operation before you do the operation, you have the opportunity to tailor your approach, to tailor your team to the specific environment and event. Think about that opportunity.”

Weinstock’s printer now runs 24/7 preparing for procedures at Boston Children’s — well worth the $400,000 investment.

The models are game-changing — giving a whole new meaning to personalized medicine. With each new print, the models are getting more sophisticated. Soon, the replicated veins and arteries will bleed as they would in real-life.

Boston Children’s has also found better recovery times. Patients of surgeons who’ve practised on the models typically leave hospital sooner and get back on their feet more easily.

Weinstock’s simulation program really took off a few years ago with Surgical Sam, the world’s first operable infant mannequin.

A model of an individual

But Weinstock wanted not just a model of generic human but one of a specific person.

That’s also what Adam Stedman needed. Adam was born witharteriovenous malformation or AVM, a tangled mess of arteries and veins in the brain that restricts blood flow and prompts progressively worse seizures that can cause brain damage.

He could have had a stroke at any moment, or a hemorrhage, his mother Amy tearily explained. But surgically tackling the web of tubes inside Adam’s brain was also potentially deadly, or it could leave him blind.

The 3D printer re-created Adam’s brain — including the AVM — something his surgeon could hold, manipulate, examine, re-examine and ultimately, practice on.

The surgery was a success — taking only a third of the expected time because the entire operating room team had done it before just hours earlier on the practice model.

When Adam came out of the OR, he smiled and his mother broke down. “He just has a blind spot,” she said in an interview in her Connecticut home. To her, that’s a big improvement.

“I honestly think that the 3D printing has the majority to do with that, as far as where they knew, where to cut and where not to.”

cbc.ca

by David Common, CBC News | Apr 04, 2015 5:00 AM ET