PLA welding is a way to fill in gaps or “glue” 3D prints together.
Using a power drill with a small piece of PLA filament instead of a drill bit, the rotating filament is pushed against the 3D printed plastic. This generates friction, which heats up the filament and softens it. The filament is then free to fill in a crack or weld plastic together. After cooling, this creates a strong bond, as if it had been part of the piece all along.
Inspired by friction welding, a welding technique typically used to fuse metals, PLA welding applies the concept of utilizing rotational friction to plastics instead. Friction welding is often used in industry to join dissimilar materials at more stable temperatures than other welding methods. Applications include the aerospace and automotive sector, joining together turbine shafts, car frames, and more.
PLA welding takes advantage of the uniquely low melting point of thermoplastic filament. This means a standard power drill is more than enough to create friction for welding. There’s no need for any specialized tools, which is great news for everyone!
In the following, we’ll take a look at for which situations PLA welding is best suited and then move on to a step-by-step guide.
Though most people stick to superglue to connect printed parts, there are times where glue just doesn’t cut it. In these cases, PLA welding can really save the day. Some common situations include:
Ultimately, there are always alternatives available (which we’ll cover later on), so the method you choose is a matter of personal preference. That said, PLA welding is a quick, versatile, and effective method when mastered – so it’s definitely worth a shot.
Another thing to note is that PLA welding works better when there’s some sort of channel for the filament to fill up, rather than trying to join two flat pieces. This way, the weld reaches deeper into the part and is able to make a stronger bond. To achieve this, you can design a bevel into your part or create one manually with a soldering iron.
For PLA welding, you’ll need the following:
Power drills and collet packs can be easily found in hardware stores if you don’t have one already. We don’t need anything too fancy for our purposes. Alternatively, most maker spaces may have a power drill available for those who don’t want to buy one outright.
To set up, put your collet into the drill and insert your filament, tightening the collet into place. Cut the filament about 15-30 mm from the collet. As you’ll quickly find, longer pieces of filament can be very difficult to control. We want enough filament to work with, but not so much that we can’t wield it properly.
It’s also important that the filament is as straight as possible. Use your fingers to straighten any curves. A heat gun or even hair dryer may come in handy if the material doesn’t cooperate.
So, you’ve set everything up and are ready to weld. Now what?
The speed of the drill can make a huge difference in welding. Too fast and you might find filament flying everywhere and things spiraling out of control. Too slow, however, and it may take a long time for enough heat to build up to melt the filament. Start out with a medium setting, and adjust according to your needs.
Another thing to watch is how much pressure you put on the seam. You want to create friction and penetrate into the plastic, but do it too much and you’ll end up snapping the filament. It helps to angle the filament at 45 degrees to prevent the piece from bending too much.
Welding does take some technique. Especially for beginners, it’s recommended to try it out on some scrap pieces first. With practice, you’ll become an expert in no time!
There are many types of welds you can create depending on how you move your drill around. Here are the two main ones:
For an overview of even more techniques, try this video by Polymaker.
Each weld has a slightly different appearance, and some find it easier to weld one way than the other. Welding is sometimes more art than science, so don’t be afraid to combine different techniques or even make up your own.
Ideally, the best welds are built up in layers. If you have a large channel to fill, especially if it’s wider than your filament width, let each layer cool before starting the next one. This ensures a deep and secure join.
Welding may leave bumpy trails behind. Post-processing is essential to getting that perfect, seamless joint. So what’s the best way to smooth the bumps out and finish your PLA weld?
To get the best results, you can combine both methods. It’s surprising how stunning the final product can turn out. For more detail on the exact procedure, refer to this article on PLA smoothing.
And with that, we’ve completed our PLA weld!
As promised, here are some alternatives to PLA welding:
Feature image source: 3D Printing Nerd / YouTube
License: The text of "PLA Welding – How to Fuse PLA Seams and Cracks" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.
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