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How to Glue 3D Printed Parts

You’ll often need to join 3D printed parts together. Whether you’ve split a large model up into separate chunks so it will fit on your print bed or simply need to make a repair.

Thankfully, no matter which material you’re 3D printing with, from PLA and ABS through to TPU and UV resins, there are many different ways to glue your prints successfully. You just need to pick the right glue and prepare your prints properly to get the strongest joint.

Quick Summary

PLA – 1st Epoxy, 2nd Superglue, 3rd PLA in a 3D Pen

ABS – 1st ABS cement, 2nd Acetone, 3rd Epoxy

TPU/TPE – 1st TPU in a 3D Pen, 2nd 3M DP8005, 3rd Loctite Plastic Bonding with Activator

Designing for Bonded Joints

If you know you are going to glue your print together, then you should design the bonded areas with this in mind.

Larger Area equals Stronger Bond

Glue works best when it has lots of surface area to stick to so you should try to locate the bonded join on a large section of your print.

To help increase the strength of the bond, you can design in features like castellations or dovetails that will increase the mechanical strength of the joint as well as giving more bonding area.

Areas with small cross-sections will be under more mechanical stress and therefore more likely to bend and break so you should try to avoid putting bonded joints in these areas.

Hide the Join

You should try to locate your bonded join where it will be less noticeable. Try positioning it on flat areas or where there is an overlap that will disguise it. Joins on highly curved or detailed surfaces will be more noticeable and harder to match the two sides together.    

Preparing 3D Prints for Bonding

Once your segmented parts are printed, you should remove them from the build plate and remove all the support material and clean up any imperfections.

You can use pliers or wire cutters to remove the supports. If you find some difficulty in removing the supporting material from parts, then you can remove them with sanding. Sanding will remove all the additional material easily but it takes time, and if you want an efficient way, then you can use an electric sander.

Sanding creates a lot of dust, and your fingerprints leave grease, both of which will weaken your glue bond. So next you must clean up the part with water or ideally alcohol cleaner to ensure it is dust and oil free.

Offer up the two parts to each other and make sure the join matches perfectly and the bonding faces mate to each other across the whole area not just on one or two spots. Remember, you need to get as much contact as possible between the two pieces.

When you are using an adhesive material to join the parts, sometimes you only have to use glue to join the parts but, in most cases, you have to roughen the surfaces of the components where the glue will be applied for stronger bonding. Again, this is all about creating the most surface area for your adhesive to attach itself to.

Make a detailed inspection of the whole model and make sure that all parts are ready to join.

Joining of Parts

After the complete inspection, I arrange all the parts in assembly form for joining purpose. If you don’t have clamps available, you can use rubber bands to make the model secure.

Sometimes due to the geometry of the model, rubber bands won’t help so you can also use tape or straps in that case.

Of course, you have a 3D printer, so if you don’t have any G-clamps you can print some!

There are several types of glue and methods to join 3D printed parts, and the best option will depend upon the geometry and the material you’re using.

Superglue

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The most common type of adhesive used for bonding 3D printed parts is cyanoacrylate glue, more commonly known as superglue, CA glue, or the brand names Gorilla glue and Krazy glue.

Cyanoacrylate is most notable for being very quick drying, hard to sand, and it will give strong bonds.

If you are not used to its quick setting speed or use it too messily, then you can create a lot of problems! Any drips will be harder than the material you’re bonding and therefore difficult to sand.

You can use superglue for the most 3D printing materials, like PLA, ABS, or PETG.

Superglue is not recommended for flexible materials like TPU, TPE, or Nylon.

Because superglue sets so quickly, you often won’t need clamps or bands to hold your prints together as a 30-second hold in your hands will be enough time for the glue to set.

For even quicker bonds, you can buy an accelerator spray that makes superglue set almost instantly.

Superglue bonds are strong in tension, i.e., when being pulled apart, but are weaker in shear, i.e., when the parts are slid over each other.

Another advantage of superglue is that it shows resistance to chemicals and low temperatures.

Epoxy Glue

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Epoxy is a popular two component glue that has to be mixed before use. It is slow to set so you will need to have a way of clamping your prints while the glue set. Epoxy creates a very strong bond in all directions.

Epoxy creates an exothermic reaction when it sets, which means it heats up. You should be careful when using epoxy on thin sections of PLA as the heat during curing can be enough to distort your print. Slower curing epoxies will release less heat and will not deform PLA prints.

Before you mix the epoxy, make sure that the parts are correctly fitted and surfaces or edges are prepared to join. After that, gather clamps and all the tools necessary for operation, and more importantly cover all the areas that need protection from spills.

Epoxy has a high viscosity, so it won’t drip everywhere, and also has excellent resistance to temperature and chemicals. It is slow drying, which is an advantage in the sense that you can readjust the position of the joining parts.

ABS Cement

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If you want a really strong bond on ABS parts then the plumber’s favorite, ABS cement, is a good choice. It will also work well on PLA and HIPS materials.

ABS cement is a solvent that chemically melts the ABS creating a very strong bond. As with superglue, you will need to make sure the bonding surfaces are clean of dust and grease and sanded well flat to increase the bonding area.

ABS cement is usually colored so you will need to either use it on a hidden area or cover it with paint after it has set.

Bonding with a 3D Pen or Soldering Iron

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For the ultimate hidden join, you can use precisely the same material that the rest of your 3D printed part is made from.

3D pens are operated on similar principles to a 3D printer so you can insert a short length of your chosen filament into the pen and then draw on to your print where you want the bond to be.

The downside of 3D pen bonds is that it can be hard to get a strong bond as the surrounding plastic isn’t melted.  

As an alternative, you can use a soldering iron set around 200C, this will allow you to melt the surrounding walls and infill of your 3D printed part before introducing new molten filament to create a bond or fill a gap.

It can be hard to use a soldering iron without causing damage to your print.

Solvent Bonding with Acetone

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Acetone is well known in 3D printing circles for making your ABS and HIPS prints go super smooth by bathing them in a vapor bath. You can also use Acetone as a very successful glue for both ABS and PLA. In fact, it’s the perfect glue for bonding PLA to ABS.

You can find the acetone readily available in the market, and it’s very cheap. You will need a brush to paint acetone on to the surfaces of the parts. You then press these parts together by the support and wait for the parts to join. The joining depends upon the amount of acetone used and the surface area of the parts. It takes a few minutes to some hours in joining. 

In simple words, this technique works by melting plastic chemically on the surfaces that are to be joined. The solvents are brushed on parts or surfaces and then mated together, or it can be used in an existing crack. This method made joints which are stronger than many adhesives.

An important advantage of the Solvent joint over epoxy and superglue is that after evaporation the joint part will contain only FDM material and so will be unaffected by things like water.

Joining with Friction 

Friction welding is the process of rubbing two materials together at speed, so they heat up and melt into each other.

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In industry, this method is used to join the large metal workpieces that will require a high time-consuming welding process.

If you have the Dremel tool, then you can place a short approximately 1-inch length of filament into the chuck. After that, you can increase its speed and apply pressure on the surfaces or edges you want to join. You will surprisingly find that the joint made by this process will be very strong.  

It is beneficial for joining parts that will, on the other hand, require large areas or for assemblies that will work under high stresses.

The downside of a friction welding joint is that it will be quite untidy and rough, so you may need to sand it down and apply some filler to neaten it up.

You can get creative with friction welding and use a different color filament for the welding material and create some attractive looks.

Filler Material

You can also use any of these glues as a filler to fill in any gaps. Superglue mixed with talc or bicarbonate of soda makes a very strong filler.

Frequently Asked Questions

I get asked plenty of questions about how to bond 3D printed parts. Here are the most commonly asked ones. If you have any more questions, please ask me via the contact option or in the comments below!

Can I use a hot glue gun to bond 3D printed parts?

You can use a hot glue gun to bond 3D printed parts, but it won’t be very strong or long-lasting. A hot glue gun is suitable for a temporary bond, especially if you are bonding different materials to your print such as glass or metal but it will struggle to bond to PLA or ABS strongly.

What is the best glue for PLA?

PLA can be bonded with Superglue (Cyanoacrylate), epoxy, and even Acetone. A two-part epoxy will give you the most durable bond on PLA, but you will need to hold the parts together with clamps while it sets. I’ve had good results using an ABS cement on PLA.

In most cases, superglue will be more than adequate for bonding PLA, and it’s very quick!

Can you superglue/gorilla glue PLA?

Yes! Superglue is one of the quickest and easiest ways to bond PLA. Just be aware that it will set very quickly, and once it’s set, it will be hard to separate!

How can I bond flexible filaments like TPU (NinjaFlex) and TPE?

Bonding flexible filaments are difficult because they are low surface energy materials (LSE) and to create a bond, you must use a glue that has lower surface energy than the plastic.

One of the few types of glue that will bond TPU is 3M Scotch-Weld Structural Plastic Adhesive DP8005. Unfortunately, it is quite expensive, but it will give you the best bond on flexible filaments.

Alternatively, some people have had good success bonding NinjaFlex with Loctite Plastic Bonding System with Activator. The key seems to be the use of the activator.

Happy Printing!

-Dylan

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