There is an overwhelming amount of material to choose from with 3D printing – even with desktop FDM printers. For the casual maker, printability and appearance are often all that matters, especially if you are printing mostly decorative items. But when you’re trying to create a functional object, how do you know which material will best suit your needs? This is not an insignificant question, especially when the item you are printing is going to be responsible for its structural functions. How do you know if your filament is strong enough?
MatterHackers is often asked this question. The retailer has one of the largest filament selections in the 3D printing industry, so their team knows a lot about filament and filament thickness. After repeatedly asking MatterHackers what type of filament is the strongest, they decided to run some tests to find out the answer.
“Strength, however, is a bit vague as it can refer to a number of different mechanical properties – tensile strength, yield strength, fatigue strength, compressive strength, and impact resistance – so it is difficult to answer this question without further information.” Taylor Landry of the MatterHackers team warns. “… We are not a test laboratory and cannot perform scientific tests on these mechanical properties, and we certainly have not found a Young’s modulus. What we can do is do a comparison test – put 3D printed parts through the same test and see how filaments compare to each other. “
To test different materials, MatterHackers decided to 3D print an object that was as strong as possible: a carabiner. They scaled their model to be about the size of a typical aluminum carabiner you can find at a hardware store that is rated for 150 pounds. They printed each test model on a Rostock Max with a 0.4 mm nozzle at 0.25 mm layer height and 50% triangular pattern fill with five perimeters and five solid top and bottom layers.
The team then mounted a force gauge on a block and tackle pulley system at an 8: 1 ratio, which means that for every pound that was 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 ratchet cable until the carabiner failed. The dynamometer recorded the peak strength for each.
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,” explains MatterHackers. “Because it is not very stiff, it just bent and deformed until it came off the test bench. This toughness is obviously a very useful trait, but it’s not an ideal material for something like this carabiner. “
Unsurprisingly, PLA did badly and PETG didn’t do much better. NylonX was a welcome surprise though, showing up to be 100% stronger than PLA and 60% stronger than ABS on average. Polycarbonate also performed well, but was also the most difficult material to print as it required thorough drying before printing and was prone to warping.
The team also tried printing some carbines on a Markforged 3D printer. Markforged is known for its fiber-reinforced nylon 3D printing materials. MatterHackers printed two carabiners with glass fiber reinforced material and two with carbon fiber reinforcement. Surprisingly, all four parts fared worse than the NylonX and Polycarbonate parts for reasons that MatterHackers said are not entirely clear – they plan to investigate the matter further in the near future, as they have received incredibly strong parts in the Mark-Forged Materials Past.
Of course, the tests weren’t just simple measurements of tensile strength, the team found. Stiffness was also a factor.
“While we tensioned the 3D printed carabiners, we didn’t just measure the tensile strength. We found that the latch’s integrity and the ability to stay closed for as long as possible was a big factor in the maximum pre-failure load. The more flexible the filament, the easier it is for the latch to come loose and this leads to failure more quickly. “
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 instead of breaking. Perhaps most of all, MatterHackers’ testing has proven that strength is a complicated thing and that what works best for one application may be completely wrong for another. A 3D printed carabiner is also a cool way to carry your keys around. However, if you do go mountain climbing, it is best to buy an aluminum carabiner from the sports store. Discuss in the MatterHackers forum on 3DPB.com.
