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Weathering of 3D Printed PLA Objects
We've received questions about how 3D Printed parts handle weather and exposure. It's been just over a year since my post about the 3D Printed Garden Tools. The slug trap in that post received the most attention, and was also the most structurally interesting. When spring was over and the great slug war abated, I decided to leave the trap out to see how the PLA would handle the elements. Here are the results.
Here was the original trap when it was fresh off the printer.
Throughout the spring, the trap set on the ground full of cheap beer (and often slugs). Once it had served its purpose, it was moved to the top of a metal drum where the conditions would be the harshest. This metal surface (and the slug trap) was in full sun through the heat of the summer, in the rain through the fall, and completely exposed through the winter. The drum lid has a lip on it that retains water when it rains or snows, so the trap was often sitting in standing water, including through many freeze-thaw cycles. Summertime temperatures reached 102F, and daytime highs averaged 91F (average taken over the month of August). Here it is in that standing water after sitting out for more than a year.
This trap was printed in our old PLA, the same blend and color as the translucent green you see from many suppliers. As you can see, the color has faded, and somewhat inconsistently.
Dirt has settled into some of the grooves between layers, making them more pronounced. The sloped roof had the most problems. This print was done as a very quick print with a single perimeter. These perimeters have shrunk and pulled apart a little bit, which has allowed dirt into the interior, making it appear more faded than the base.
The base was also printed with a single perimeter, but the vertical walls give the perimeters more overlap, which made it less prone to cracking, though you can see they've still pulled apart some regardless. Here you can see the (mostly) vertical wall of the base of the slug trap.
Looking at the bottom you can see that the surface is still tight and crack-free. Though dirty, it's still smooth and in good condition.
Structurally, the trap seems to be about as tough as it was before. The part is still rigid and strong. The vertical walls and flat bottom of the inside are still water-tight.
On this particular print, one of the posts that holds the lid up had broken off shortly after printing. I glued this back in place with super glue. The bond of this glue doesn't seem to have weakened, as the post is still sturdy.
When printing for prolonged outdoor use, make sure to print multiple overlapping perimeters and make sure you're getting good bonding between traces to keep dirt and moisture at bay.
Be warned that PLA won't do as well in closed areas that get particularly hot. Cars are a good example. In the kind of heat experienced there, you will likely see deformation.
If anyone has any examples of how their PLA (or ABS) printed parts and objects have fared outdoors, we would love to see your photos and hear your thoughts.