How to Join a 3D Printer Filament? – 4 Easy Steps

Every 3D printing enthausants thinks what to do with leftover filament because there’s always a certain length of filament left, especially in bowden printers. People want to connect this leftover filament with new filament instead of throwing them in trash can or sometimes, they want to print with different colors like rainbow without changing the filament too frequently. So, how can you do this? Here’s a detailed guide on how you can join 3d printing filament.

How to join a 3d printer filament?

There are many ways you can join two filaments together. You can use a DIY method like rolling the end of the filament in a thin foil, then use a lighter or soldering iron to heat it and fuse them together. After that, take a sharp cutter to cut the bulge. As an alternative, you can use a splicer or joiner. But let’s say you want something more professional than you can get Mosaic Palette 3, which is basically a magic box that cuts, splices, fuses, and cools the filament with perfection.

Welding filament: What you should know

Well, there could be many reasons behind joining two filaments together. But if you ask for my personal opinion on this, I highly don’t recommend welding filaments together. There is a high chance the weld might be bulgy and won’t pass through the extruder. Or, if you attempt to join them using a DIY method, you might end up boiling the filament which can affect its properties and may not get properly print quality or might cause a clog.

You might think that I’m printing something that requires more than one spool of filament, so joining another one seems like a wise choice but modern 3D printers are equipped with filament runout sensors. So, if your 3D printer runs out of filament, it will automatically pause the print until you load the filament again. You can also get a filament runout sensor and install it on your printer.

4 Ways to Join 3D printing Filament 

Simple Method (No tools required):

This method is the simplest and easiest one to do at home.You don’t need many tools – You only need one of these: a lighter, soldering iron, or heat gun, and you’re ready to start the welding process.


  • First of all Trim the ends of both filaments at a 45 degree angle
  • Heat the ends using a heat gun,lighter or soldering iron until they become soft or slightly molten but don’t heat it too much otherwise you might burn the filament.
  • Press the molten ends of both filaments together, overlapping each other slightly.
  • After heating the filament, press them together on a flat surface to make sure the joint is flat and smooth.
  • Let it cool and solidify and then if there’s a bulge use a sharp cutter to trim the excess filament until you get the diameter of 1.75mm or close.

PTFE Tube Method

In the last method you did it on an open flat surface which increased the requirement of post processing but with this method you can get even better finishing and will require less post processing work.


  • Like in previous step, cut the ends of both filaments at a 45 degree angle
  • Heat the ends using a soldering iron or a lighter until they become soft or slightly molten
  • Take a small length of PTFE tube and hold it using VICE or download the filament splicer STL file which uses PTFE tube.

            STL –

  • Insert one filament from one side and the other from the opposite side and make sure they’re in their molten phase.
  • Press the molten ends of both filaments tightly toward each other.
  • Take out the filament, and voila! You’ve achieved a good finish. Then, use a piece of 100-grit sandpaper to smooth it out until it can easily go through the extruder and PTFE tube.

The Knot Method (Only Applicable on Flexible Filaments)

The above two methods are best for welding hard filaments like PLA, ABS, PETG, Hips, or nylon. But what about flexible filaments? You can use the knot method to weld flexible filament, but it will require a little bit of practice and precision and there will be a bit more post-processing involved, such as trimming the bulge using scissors or a cutter compared to the previous two methods.


  • First of all tie a tight, very small knot between the ends of the two filaments to make sure it won’t cause any problem of huge bulge and also reduce the post processing work
  • Then trim the excess filament close to the knot.
  • Heat the knot properly using a heat gun or lighter to melt it, but don’t over-melt it to the point where it breaks. Do it gently, and it’s better if you use a heat gun with temperature control.
  • After this, precisely trim the excess filament and the bulge. Since it’s flexible, make sure to do it slowly and carefully so you don’t cut the filament. Use a very sharp cutter for this step.

The Professional Method 

If you’re really serious about the filament splicing game and willing to spend $700 to $900, then this method is for you. Presenting to you Mosaic Palette 3, it is a professional filament splicing tool specifically designed for multi-material and multi-color 3D printing. It allows users to use up to 4 different filaments without changing the spool while printing, as it automatically does everything from cutting to splicing precisely with zero compromises in print quality.

Steps: (This is a short overview; follow the user manual that comes with the machine.)

  • First of all connect the Mosaic Pallete 3 with your 3D printer according to the user manual.
  • Load the different filaments you want to print with into the machine
  • Well, I think that’s it, as Palette 3 will automatically handle the rest from here – creating a precise splice of two filaments and then loading and unloading the filament too.


To properly weld filaments, you might need to practice a little, especially with heating, as excessive heat can ruin your weld. If you are very serious about filament welding and willing to spend money then go Mosaic Palette 3 or any filament splicing tool to get finest results. If you ask me then, personally, I’m not a big fan of filament welding, as modern 3D printers come with filament runout sensors. If you’re interested in multi-color printing through filament splicing then there are many multi-color 3D printers available in the market, such as Bambu Lab’s A1 Mini, Carbon X1C, and P1P, etc.


How do you join two pieces of filament together?

  • To join two filaments, you can use a simple DIY method: trim the filament ends at a 45-degree angle, heat them using heat gun or lighter until soft, press the molten ends together or you can use a professional tool like Mosaic Palette 3 for precise and automated filament splicing.

How do you attach 3d filaments together?

  • Attach 3D filaments by trimming their ends at an angle, heating them until soft, pressing them together then trim the bulge with a cutter. For better results and less post-processing, consider using a PTFE tube to join the filaments.

How does palette 3 work?

  • Mosaic Palette 3 is an automatic filament splicing tool, just connect it to your 3D printer according to the user manual, load different filaments, and Palette 3 will handle the rest. It precisely splices filaments and allows you to do multi-material and multi-color 3D printing without any reduction in print quality.

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