There is an overwhelming amount of material to choose from in 3D printing – even just when it comes to desktop FDM printers. For the casual maker, printability and appearance are often all that matters, particularly if you’re mainly printing decorative items. But when you’re trying to create a functional object, how do you know what material is going to best fit your needs? That’s not an insignificant question, particularly if the item you’re printing is going to be responsible for any weight-bearing functions. How do you know if your filament will be strong enough?
That’s a question that MatterHackers gets asked frequently. The retailer carries one of the largest selections of filament in the 3D printing industry, so their team knows a lot about filament and filament strength. After being asked again and again about what type of filament is the strongest, MatterHackers decided to do some testing to find out the answer.
“‘Strength’, however, is a bit vague as it can refer to a few different mechanical properties – tensile strength, yield strength, fatigue strength, compressive strength, and impact strength – so it’s a difficult question to answer without more information,” Taylor Landry from the MatterHackers team cautions. “…We’re not a testing lab and we can’t perform any scientific tests of those mechanical properties, and we surely didn’t find a Young’s Modulus. What we can do is perform a comparative test – putting 3D printed parts through the same test, and seeing how filaments compare to each other.”
To test different materials, MatterHackers decided to 3D print an object that better be as strong as possible: a carabiner. They scaled their model to approximately the same size as a typical aluminum carabiner you can find at the hardware store, rated for 150 lbs. They printed each test model on a Rostock Max with a 0.4mm nozzle at 0.25mm layer height and 50% triangle pattern infill, with five perimeters and five solid top and bottom layers.
The team then rigged up a force gauge to a block and tackle pulley system with a 8:1 ratio, meaning that for every one pound applied to one side of the system, eight pounds were applied to the other side. They tested each carabiner by attaching it to the pulley system and applying tension with a ratcheting cable until the carabiner failed. The force gauge recorded the peak force for each one.
The results are as follows:
“Somewhat surprisingly, Taulman 645 failed at the lowest weight of any filament we tested, but it was the only filament that didn’t break,” MatterHackers states. “Because it’s not very rigid, it just bent and deformed until it came off the test rig. This toughness is obviously a very useful characteristic, but it’s not an ideal material for something like this carabiner.”
PLA, unsurprisingly, performed poorly, with PETG not faring much better. NylonX, however, was a welcome surprise, showing itself to be 100% stronger than PLA and 60% stronger than ABS on average. Polycarbonate also performed well, but was also the most challenging material to print with, requiring thorough drying before printing and having a tendency to warp.
The team also tried printing a few carabiners on a Markforged 3D printer. Markforged is well known for its fiber-reinforced nylon 3D printing materials, and MatterHackers printed two carabiners with fiberglass-reinforced material and two with carbon fiber reinforcement. Surprisingly, all four of the parts performed worse than the NylonX and Polycarbonate parts, for reasons that aren’t quite clear yet, according to MatterHackers – they’re planning to explore the matter further in the near future, having gotten incredibly strong parts from Markforged materials in the past.
Of course, the tests weren’t just straightforward measurements of tensile strength, the team came to realize. Stiffness was also a factor.
“While we were applying tension to the 3D printed carabiners, we weren’t just measuring tensile strength. We found that the integrity of the latch and the ability of it to stay closed as long as possible was a huge factor in the max load before failure. The more flexible the filament is, the more easily the latch unseats/opens, and this leads to failure more quickly.”
Thus, while Taulman 645 performed poorly, that doesn’t mean it isn’t a strong filament – in fact, it essentially returned to its original shape after the weight was removed, rather than breaking. What MatterHackers’ test may have proved most of all is that strength is a complicated thing to gauge, and that what works best for one application might be completely wrong for another. Also, a 3D printed carabiner is a cool way to carry around your keys, but if you’re going mountain climbing, you’d best buy an aluminum one from the sporting goods store. Discuss in the MatterHackers forum at 3DPB.com.