Oct. 23, 2014

3D printers create objects layer-by-layer from the bottom up, but this poses a challenge when printing overhanging or protruding features like a figure's outstretched arms. They must be formed using supporting structures - which are later removed - adding time and material to the process.

Now, researchers from Purdue University have demonstrated two approaches that significantly reduce the time and material needed to produce objects with 3D printers. Such improvements are likely to result in lower overall printing costs, said Bedrich Benes, a Purdue associate professor of computer graphics.

"The total cost of printing is governed by numerous factors, including not only the price of the printer but also the amount of material and time to fabricate the shape," he said.

The first one, the new PackMerger algorithm, works by printing a project in segments that can be glued together. For example, Benes said, printing a model of the Gateway Arch is completed by first dividing the arch into segments before printing.

"Our algorithm cuts the project into small elements that will fit into the printing tray," Benes said.

A 3D object was automatically divided into a set of similarly sized segments that can be easily assembled together and printed. The overall printing time was reduced from 13.5 h to 9.5 h (saving 30%) and the amount of support material was reduced from 351 g to 229 g (saving 34%). The optimization was completed in approximately 1 min and the final object assembly took about 15 min.


The algorithm determines how to pack the most elements into the smallest possible space using the same principle employed by the Tetris tile-matching puzzle game, in which tiles are manipulated with the aim of creating a horizontal line of blocks without gaps.

"To the best of our knowledge this is the first fully working 3-D volume-packing algorithm," Benes said.

An object larger than the printing tray (shown in the figure) (a) was automatically segmented into pieces that fit the tray (b) and it was printed in a single print (b). It was then assembled in less than 5 min (c).

The algorithm prints the segments so that they are spaced as closely together as possible in the printer tray. Because they are packed together, there is little supporting material between them, saving both time and material. The segments can then be separated and assembled. The algorithm sometimes instructs the printer to produce items nested within each other to save space.

The research paper detailing the PackMerger algorithms have been published here.

Benes and Purdue doctoral students also have developed another algorithm that results in smaller support structures, reducing printing time by an average of 30 percent and the quantity of material by an average of 40 percent.

New software algorithms reduce the time and material needed to produce objects with 3D printers. Here, the wheel on the left was produced with conventional software and the one on the right with the new algorithms. (Source: Purdue University/Bedrich Benes)


Before printing the object, the algorithm determines how it should be oriented on the printer tray so that the overhanging area requiring support is minimized.

"The computer automatically rotates the object in all possible orientations before printing to find the orientation that has the smallest overhang area," Benes said.

The support material generated by the built-in 3D printing software for MakerBot Replicator 2 a) and the amount of support material b). Our solution c) reduces the amount of the support material d) leads to faster printing, and higher quality of the fabricated model.

Then supporting structures are built only at certain points within this area, resulting in a scaffoldlike structure that effectively supports the overhangs. The algorithm uses a "geometry-based" method that does not need to consider structural or physical properties when determining how to reduce the supporting elements.

"The main advantage of it being geometry based is that it saves time and money and printing material," he said.

Research findings are detailed in a paper "Clever Support: Efficient Support Structure Generation for Digital Fabrication" here.

Posted in 3D Software

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Risc wrote at 10/24/2014 7:07:20 PM:

As MeshMixer does... also photoshop.

Bogdan wrote at 10/24/2014 7:39:48 AM:

The second finding is very interesting, lets hope they put these findings in some slicer software that can prove it too.

Tarjei Knapstad wrote at 10/23/2014 11:29:09 AM:

I wish 3ders.org would become better at providing links to sources... The original news article from Purdue: http://goo.gl/6jJ67M Bedrich Benes site: http://hpcg.purdue.edu/bbenes/ PDF for the PackMerger algo: http://hpcg.purdue.edu/bbenes/papers/VanekCGF14.pdf A demo video on Youtube for PackMerger: https://www.youtube.com/watch?v=sBgSr7JItmo PDF for the support structure paper: http://hpcg.purdue.edu/bbenes/papers/Vanek14SGP.pdf

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