March 17, 2014

Measuring 3D Printed Material Strength

The word "open" is certainly a buzzword in 3D printing, but what does that really mean? While many are tossing around this phrase, few actually practice an open business and product philosophy. Open Source Hardware (or Libre Hardware), notably led by the RepRap project, is experiencing rapid, cross-industry adoption. This philosophy empowers engineers, makers, builders, and creators with unprecedented freedom to change, update, and modify their products over time.

Pictured: A specimen in load frame, testing material strength. Credit: Michigan Technological University.

Such developments represent a significant shift from historically closed-sourced options in the marketplace, which are often developed with proprietary software and hardware that ultimately limits how people use them.

Being open is a good start, but is the technology effective? More specifically, how strong are 3D printed materials when printed with open source hardware? Dr. Joshua Pearce, an associate professor of Materials Science & Engineering and Electrical & Computer Engineering at Michigan Technological University, asked the question of "strength," and the answer may surprise you.

In a recent study, Pearce and his team examined the basic and tensile strength and elastic modulus of printed materials in acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) using a range of open source hardware. They found average tensile strengths of 28.5 MPa (megapascals) for ABS and 56.6 MPa for PLA, with average elastic moduli of 1807 MPa for ABS and 3368 MPa for PLA.

The study concludes, "It is clear from these results that 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."

These results aren't surprising to our R&D team at LulzBot, makers of open source 3D printers, including the recently launched TAZ 3. As discussed in my previous EE Times blog post, we use a cluster of 135 LulzBot 3D printers to print durable parts for end products and prototypes for new products. For example, the Open Source Ecology team uses LulzBot 3D printers to create prototypes and parts for heavy machinery such as tractors, soil pulverizers, and compressed earth brick (CEB) presses. Meanwhile, at the Open Hand Project, LulzBot technology is being used to develop low-cost robotic prosthetic hands.

It is important to understand that the question of print material strength is complex. It has not already been answered because most users have neither access to reliable, cost-effective means to test the strength of their parts, nor the technical expertise that Pearce and his team have to investigate aspects such as patterns, layer height, and strength.

Pearce's study focuses on the tensile strength in the plane of the print bed with two types of print materials. Future research can be performed considering interlayer adhesion and a wide range of additional filaments that can be printed or those yet to be developed.

For more information, you can read the full study, entitled "Mechanical Properties of Components Fabricated With Open-Source 3-D Printers Under Realistic Environmental Conditions," which is freely available online.

Do these findings surprise you? What high-strength applications would you like to test on an open source 3D printer?

This post originally appeared on the EE Times designlines prototyping blog on March 11, 2014 here.