New algorithm makes 3D printing more efficient, less wasteful

Eric Hopton for redOrbit.com – Your Universe Online

We are not at that stage yet, but there may soon be a time when traditional Christmas gifts, and even decorations, become a thing of the past – thanks to new advances in 3D printing. Whatever your heart’s desire – just 3D print it.

A new algorithm, developed by computing science professor Richard Zhang of Simon Fraser University (SFU), has enabled the creation of a 3D Christmas tree “efficiently and with zero material waste”. The process uses the world’s first algorithm for “automatically decomposing a 3D object into what are called pyramidal parts.”  This pyramidal decomposition also reduces the cost of material and print time. It’s good for the advancement of 3D technology and it’s great for the environment. And, say the researchers, it’s just in time for Christmas

Zhang is a computer graphics expert who specializes in geometric modeling and processing. He developed the algorithm with PhD candidate Ruizhen Hu, an international student from Zhejiang University in China. Together, they have produced a research paper, Approximate Pyramidal Shape Decomposition, which was published this month in ACM Transaction on Graphics. Hu also presented their research at a major graphics conference, SIGGRAPH Asia, this month in Shenzhen, China and the team have posted images of their admittedly tiny tree online here.

The building blocks for the process – the pyramidal parts – have a flat base with the remainder of the shape forming upwards over the base with no overhangs, very much like a real pyramid. This is an optimal design for 3D printing, say the researchers, because “it incurs no material waste and saves print time.”

Zhang and Hu are convinced that the algorithm will be a big step forward in the world of 3D printing. They also believe there will be a lot of interest from those who make applications for designing molds and for casting.

The paper describes how, in current methods of 3D printing, the printer deposits melted plastic layer by layer in a bottom-up fashion. When the shape has an overhang – the branch of a Christmas tree is a great example – extra material has to be printed underneath it to provide support. The problem is that this extra “supporting” plastic is just waste material and has to be removed. It also wastes time which is bad news, especially in industrial and commercial projects. The SFU researchers also found that removing waste material which supports an object’s hollow interior or tiny fragile parts, like the star atop a Christmas tree, can be just about impossible without causing breakage.

“Coming up with a practical algorithm to decompose 3D objects into the smallest possible number of pyramidal parts was quite a challenge,” says Zhang. “Importantly, it is impractical for most real-world objects to be broken into exactly pyramidal parts since this would result in too many parts,” he says.

Zhang is quick to credit Hu with finding a “really clever way of transforming the problem to obtain an effective solution.” This was the new algorithm which works by partitioning the object into a small number of nearly pyramidal parts that can be 3D-printed and almost eliminates material waste. These printed parts are glued together to form the finished object. The Christmas tree, for example, is created in two halves during fabrication before being glued together.

Zhang believes that the process would work well in molding and casting. “The ideas are similar,” he says. “If the molded or cast parts are pyramidal, then removing the mold or cast after fabrication would not result in any breakage.”

Professor Zhang then puts on his Christmas party hat when he suggests that “chocolatiers could use the algorithm to design chocolate molds for Christmas trees or reindeer.”

Or maybe, Professor, chocolate socks and scarves which at least we could eat – unlike all those unwanted presents that end up in the bottom drawer.

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