Feb.28, 2014

The idea of a do-it-yourself manufacturer is really coming to the forefront. The development of the RepRap, an open-source self-replicating rapid prototyper, has made 3D plastic printers readily available to the public because of their extreme low costs. Commercialized RepRap derivatives like the Lulzbot TAZ sell for around $2000 assembled and a basic kit to built a RepRap can cost less than $500.

A common criticism of home 3D printers is that whilst they can easily replicate any number of shapes and objects, and print parts that look identical to plastic prints from professional 3D printers, they can only print flimsy plastic trinkets. Are RepRap prints as strong as professional 3D printed parts using the same polymers?

Most home users have no way of testing the strength of their parts and no extensive information is currently available about the mechanical properties of parts printed specifically on RepRaps.

"We were curious too. Our prints seemed strong, but we wanted to engineer robust scientific equipment and tools for the developing world, so we needed solid trustworthy numbers." said Joshua Pearce, an associate professor of Materials Science & Engineering and Electrical & Computer Engineering and Michigan Technological University.

Pearce and his team conducted a study on mechanical properties of components fabricated with open-source 3D printers. The study used standard test methods, except for changing the environmental conditions to be equivalent to those used for home-printing rather than controlled lab settings.

Rendering of the shared .STL filed of the ASTM D638 tensile standard

Photo of a specimen in load frame / credit: Michigan Technological University

RepRap variants currently fabricate objects primarily from acrylonitrile butadiene styrene or ABS (the same plastic as Lego bricks) and polylactic acid or PLA, which is a biodegradable corn-based plastic. The study quantifies the basic tensile strength and elastic modulus of printed components using realistic environmental conditions for standard users of a selection of open-source 3D printers. The results find average tensile strengths of 28.5 MPa for ABS and 56.6 MPa for PLA with average elastic moduli of 1807 MPa for ABS and 3368 MPa for PLA.

credit: Michigan Technological University

Pearce says, "The results of the study are clear - parts printed from tuned, low-cost, open-source RepRap 3-D printers can be considered as mechanically functional in tensile applications as those from commercial vendors. In many cases they were actually stronger than the results reported in the literature."

"This study only looked at the tensile strength in the plane of the print bed, next we need to expand this study to look at interlayer adhesion." The researchers plan to also expand the study to look at other polymers as the development of the RecycleBot and open-source commercial variants like the Filastruder enable a wide-range of waste plastics to be recycled into 3-D printer filament.

"These results add to the preponderance of evidence that mass-scale distributed digital manufacturing with open-source 3-D printing is technically possible." Pearce concludes.

The study, "Mechanical properties of components fabricated with open-source 3-D printers under realistic environmental conditions" by B.M. Tymrak, M. Kreiger, J. M. Pearce is made freely available here.


Posted in 3D Printing Technology


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HowTough wrote at 9/7/2015 1:59:56 PM:

Please please do the interlayer adhesion tests. Thank you :)

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