Sometime ago a project required a method of attaching a unique machine thread to a vertical post. As the project was going to be deployed semi-permanently it needed to be as durable as it possibly could. However, what we didn't expect is how strong the result would be - a useful trait for physical prototypes that need to be outdoors.
Almost a year later, the posts needed to be removed from the ground. This provided an opportunity to evaluate the strength of the posts and to determine if any improvements could be made.
First thoughts: when the posts were finally removed, it was surprising how strong they felt and how they still had the same brilliant white paint on them. Most posts left in the dirt for a year might already be decomposing and beginning to fall apart, but that wasn't the case with the prototype.
These samples were made using an additive printing technique called filament deposition printing, or FDM for short. However, this particular type uses a filament derived from corn called polylactic acid or PLA for short. For most prototyping, product developers and end-users will want something that represents the end product as much as possible, both in appearance and function. The PLA filaments available on the market today fill this need very well. You can print a prototype using design files, and have a product in hand that looks and feels like the real thing in a few hours.
However, products made in PLA without any post-processing may have a significant flaw: heat and UV can cause the bonds between the layers of the material loosen, or warp outside of a usable shape. So this means that you may not be able to do two of the most critical tests of the outdoor product development workflow: put the prototype through any type of real usability study, or outdoor product testing, not to mention environmental ingress testing.
With the specifications of the filament in mind, one can wonder what you would expect if you put something that can not stand up to heat or UV? Let's have a look at the gallery below.
You will notice that there is paint on the items in the pictures. It serves two purposes. The first is that it allows the product to have the intended color. Second, the paint includes UV inhibitors, such as roofing paint or exterior paint; this will dramatically improve the durability of the product, at least for the duration of the product tests. For traditional PLA, this seems to be the best method for mitigating damage.
Starting with a good base material is imperative, here you will find the MatterHackers Tough series PLA offers a blend of specs for users looking for filaments purpose-built for outdoor and rugged use. In future articles, we will be reviewing these filaments and the best use cases.
Learn about how to use any of these prototyping methods in your development workflow.