3D Printer Filament Fusion: A Guide to Joining Filaments

3D Printer Filament Fusion: A Guide to Joining Filaments

In this age of raw material abundance, it’s important for users to be cognizant of wasting the filament that gives FDM 3D printing its power. By using filament efficiently and effectively, we are making strides towards not only preserving our resources but improving our processes as well. 

If you’re tired of having to constantly switch out spools of filament in the middle of a project, consider giving filament welding a try!  Filament welding has revolutionized 3D printing, making it easier than ever to add multicoloured details and textures to your models without stopping mid-print. It also provides an effective solution for when you run low on filament; instead of starting a fresh spool, simply weld the new filament onto the old one and keep going.  

3D Printer Filament Fusion

It’s surprisingly straightforward (and even relatively inexpensive) to join two different pieces of filament together to make one long piece. PLA is the most popular material used in filament welding, though it’s important to note that each type of filament requires a different temperature in order to melt so they may need to be adjusted accordingly. 

So, how do we weld two filamentous pieces together? Let’s examine the range of available techniques.

Specialized Tools for a Specific Purpose

Filament welders are an efficient and effective way to join two pieces of plastic or nylon together. Still, these tools’ effectiveness is dependent on the quality of the filament welder you choose. When looking for a good, reliable filament welder, look for one that is purpose-built. These tools have been specifically crafted and manufactured to act as filament welders, making them more effective than generic welding equipment. You can find such tools online or even 3-D print your own at home, saving you some money. 

Generally speaking, there are three main types of purpose-built welders: splicers, joiners and fusing blocks, each offering its own advantages in terms of affordability, construction and results. If you’re willing to spend more money on a more advanced machine, consider an electric-powered welding tool. They all essentially accomplish the same task, but let’s examine each in more detail.

Fusing Block

This method of filament welding uses a tool to attach two pieces of filament together without melting the other piece. The interesting thing about this approach is it requires an external source of heat, such as a light or match, to heat only one end of the filament. It’s actually quite remarkable that you can join two pieces without melting them both due to the precision and control that comes with using such a specialized tool and technique.

The process is simple yet effective – the tool itself acts as a vice or clamp to hold a length of PTFE tubing, through which one end of the filament is fed. Heat is then applied to this exposed end and quickly pulled back into the tube where it meets the other filament end. Here they will fuse within an insulated environment created by the PTFE tube. All in all, a simple and secure way to bond two filament ends together.

While it isn’t always the most reliable method without practice, it can be effective. Investing in a machine to work with on your own time is likely to be more effective than purchasing a tool already available. That said, note that the linked tool was 3D printed itself- it may be possible for users to reproduce something similar of their own depending on their capabilities. 

Splicer or Joiner

A filament splicer can be an extremely helpful tool to have when dealing with various repairs or projects, enabling the user to join together two filaments with relative ease. 

All that is required is an external heat source such as a lighter and the two ends of the filament to be joined must be inserted into the small vice-like tool so that both ends are visible within its middle opening. Then pushing the joined ends through the tool will complete the join, although some skill and precision may also be needed for this task in particular.

While splicing is not a difficult process, it does require practice to get it right – as demonstrated in this informative and amusing video. Through trial and error, makers can perfect their own designs for splicers. 

Several have shared their models online, with the most popular ones coming from marek2137, neilr98, OnTheGulf, trustfm, and pick013. Additionally, some models make use of acetone in place of heat in order to join together two pieces of filament into one.

Electric Filament Connector

While this purpose-built tool offers all the features of other tools we’ve looked at, it doesn’t come cheaply. 

You still have to plug in and heat up the electric filament connector prior to its use, but a temperature gauge tells you when it’s hot enough to use. All you need to do then is put the filament ends into the clamp and squeeze them together – though there’s no thermistor in place for temperature regulation, so make sure to turn it off soon after you’re done.

On the plus side, its own power supply means you won’t need an additional external heat source for operation, but be aware that extra convenience comes with an increased price tag.

Mosaic Palette 3

The Mosaic Palette is a groundbreaking piece of equipment indispensable to any 3D printing work. It simplifies filament management and adds automated precision to the process. With up to four filaments (for the base model) or eight (for the Pro version), users no longer need to pause their prints mid-way and switch spools. 

Also, using splicing eliminates the need for manual joining of pieces prior to printing, a tedious task that is now bypassed thanks to this revolutionary machine. To top it all off, Palette 3 allows for Wi-Fi control and requires no additional modifications to your printer; it’s certainly an attractive package that can exclusively simplify your experience.

Of course, with more features come a higher price tag. The exact cost of the Palette 3 is around $700 while the Pro’s cost is around $900 – significantly higher than other options available on the market. However, this difference in price is not unjustified as you get a lot more for your money when investing in either of these two products. Compared to some of the other tools we’ve looked at, you get much better value for your money.

Homemade Solutions for Various Challenges

With the rise of 3D printing and the ever-widening range of filaments, more and more people want to know how to weld filaments without having to buy expensive welding tools. 

Fortunately, DIYers have come up with a range of clever solutions that require minimal effort or cost. A lot of these fusion techniques can be done using household objects such as flat irons or even lighters, along with some small pieces of scrap filament. 

Household Heating Appliances

It’s incredible to think that the perfect tool for welding is probably already lying around your house, just waiting to be discovered! From whisks and kitchen knives to curling irons and lighters, there are a variety of household objects you can use as makeshift welding tools. Not only are these items easy to obtain, but they also operate under the same principles: either conductive or convective heat transfer. Take care though, as manipulating appliances for unintended use can be dangerous and require special safety considerations. Some of the tools are:

  • Hair straighteners: Using a hair straightener is one of the simpler ways to join two ends together quickly and efficiently. Its simple no-fuss approach also provides good results. For those who actively use a 3D filament printer, a hair straightener can also be used in tandem with PTFE or Bowden tubing to create a neat, protective casing while the filament is being heated. 
  • Electric iron: Similar to how hair straighteners work. But be careful not to burn your fingers in either case!
  • Hairdryer: The process is a little bit slower when hot air or convective heat is used. In this case, you would need to hold the two ends together with pliers or a vice before heating them.
  • Heat gun: To get the best results from a tool that is typically used to remove old paint from wood or walls, use the lower heat settings. Once more, pliers or vice would be useful.

Flame and Foil/PTFE

This improvised welding method is definitely not the safest way to join filaments, but it can be quite effective. All you need is two filament ends, aluminium foil or a piece of PTFE tubing, as well as a heat source such as a match or lighter. By setting up the pieces accordingly and applying heat to them, you’ll be able to connect two filament pieces together without too much hassle.

It’s an easy procedure that can even be done cheaply, however, caution is necessary since you’re dealing with heat-related applications. To achieve results that are closely akin to the fusing block method but with fewer materials involved, a small piece of PTFE tubing would suffice. 

Finally, because of its malleability when exposed to heat and temperature changes, having a bowl of water nearby would help cool down the welded parts quickly and increase their strength in the long run.


Joining filament with glue may seem intimidating, but it’s really quite simple. By using a strong, fast-drying adhesive such as Gorilla Super Glue Gel, you can easily and securely seal the two filament ends together. 

The only warning is to be careful not to get any glue on your fingers! As long as you use a small amount of glue, your filament should print just fine, although it’s worth remembering that adding additional materials to the filament may have unexpected results when printed.

Heat Shrink Tubing

 The same heat-shrinking method electricians use when connecting bare wires together works with filament just as well. This method uses a convective heat source to gently heat and shrink the tubing around the two filament ends so that when cooled it will securely fit together the two pieces almost seamlessly.   

It does require some practice though for precise temperature control and neat slicing of the tubing afterwards, but once you get the hang of this process, you can confidently create strong durable joints that integrate your projects perfectly.

The tutorial linked above can give you some extra help in tackling a task, but you may find that some of the steps or equipment needed aren’t really necessary for your purposes. If you already have them on hand, then feel free to make use of them! 

3D Pen

The 3D pen is another device that could be categorized as belonging to both the DIY and purpose-built categories.

While the length of filaments typically used in 3D pens makes it unnecessary to do any welding, the pen’s ease of use with its heat source makes it a great tool to weld filament pieces for use in FDM 3D printers. Most 3D pens have ceramic nozzles that stop the filament from sticking and make this task much easier.

All you need to do is apply a drop of heated filament to both ends, holding them together until cooled down. To help make this step even smoother, most pens come with some type of stand that can be used as an extra “third hand”. Alternatively, if you have access to a 3D printer, you could also create special inserts for a hot glue gun which serve the same purpose.

Ganesh Divte

I am Ganesh Divte. I work as a Quality Assurance Engineer at Dhruvtara WireTech PVT LTD. I have experience in SLS, DMSL, FDM, and SLA additive manufacturing processes. I am very enthusiastic about additive manufacturing and its potential to change the way we manufacture products. I believe that Additive Manufacturing has the potential to revolutionize the manufacturing industry and make it more efficient and sustainable.

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