Why Does a 3D Print Become Brittle? How To Fix It!


Printing your first 3D item can be an exciting experience. However, this experience is not void of some bumps and hitches along the way. One of these bumps is when you print your 3D model, and it comes out weak and brittle.

How do you overcome this problem? First, we would have to understand why a 3D print becomes brittle. Only then can we come up with some solutions to this situation.

Reasons behind why 3d prints turns out to be brittle :

  • The filament you used to print with is damp. Meaning it absorbed moisture from the air while sitting out, so it does not produce strong prints.
  • The temperature outside the printer is different enough to negatively affect your 3D print.
  • The quality of the filament you have used to 3D print is cheap. The already run-down filament bends and snaps easily.
  • Your 3D printer cannot extrude the filament properly because of a clogged nozzle or uneven filament diameter. It can also be because of twisted filament, or the temperature is too low, or the printing speed is too high.

So, in short, 3D prints become brittle due to filament moisture, inadequate temperature, poor filament quality, or under-extrusion.

3D Printing Is Here To Stay

Left out filament absorbing moisture and temperature disparity between filament and workspace are just some of the reasons behind your 3D print coming out as brittle.

Check out our recommended storage case to avoid this issue (Amazon link)

Low-quality filaments and under-extrusion also play a hand in printing out brittle products. You can solve this issue by removing moisture, controlling temperature, buying better filament, and more, which is what we will present in this article.

Also, check out our article on Does PLA Have A Shelf Life? How long & How To Store It for A longer Shelf Life!

What Does a Brittle 3D Print Look Like?

Before moving on to understand why a 3D print is brittle, we must first figure out what a brittle print looks like.

A normal 3D printed item is strong enough to withstand varying external force and impact, depending on the material.

PLA has a tensile strength of about 7,250 psi while ABS has about 4,700 psi (Souce) This makes any 3D item printed with PLA stronger. However, there are cases where PLA can be brittle and break more easily than an ABS product.

Your brittle 3D print will not be able to withstand as much pressure as your other 3D prints might.

Usually, a brittle print will bend and snap easily if you apply force with just your hands. The strength of the item typically does not matter how much infill is used as long as it is being printed brittle.

Another symptom of a brittle print is when it seems to be missing spots of filaments. If your 3D printed item looks like it has gaps or holes, then it is most likely weaker and brittle.

Lastly, if the layers on your print become undone or separated, it makes the entire printed structure brittle. Take a look at these pictures of a user’s brittle 3D prints, for a visualization.

Reasons for a Brittle Print

The main reasons why your 3D print might become brittle are to do with the filament moisture, temperature, filament quality, and under-extrusion.

Filament Moisture

Most filaments used for 3D printing are hygroscopic, which means they absorb water from the air. This excess moisture absorbed by the filament causes your 3D print to become brittle.

A simple test you can do to check whether your filament is brittle is to try and bend the end of your filament spool. If it bends and breaks off easily, it means your spool has probably absorbed a lot of moisture and turned brittle.

This, in turn, will make cause problems during the printing process. It will end up printing an item that will be brittle.

Temperature

It is no mystery that 3D filaments are temperature sensitive. Each printing filament has its ideal temperature at which it produces the 3D item smoothly.

ABS prints require temperatures from 210 to 250 °C while, PLA requires anywhere from 180 to 230 °C. (Source)

If during printing, the surrounding temperature varies from the nozzle temperature, it can cause the filament to break. This temperature difference will also affect the printed item and make it brittle.

For example, if it is colder in your garage or workshop, you will need to adjust your room temperature accordingly to have a smoother print.

Filament Quality

The quality of the filament you are using is also responsible for how brittle the end product will be. The cheaper in quality the filament, the more brittle the printed item is expected.

One way to find out if your filament is low-quality is to see whether it breaks easily right out of the packaging. If it does, you can expect it to produce brittle prints.

Under-extrusion

Under-extrusion happens when not enough filament is squeezed out during printing. This can lead to cracks or missing layers. Even small dots or holes can appear in layers, which makes the printed item brittle.

Some possible causes of under-extrusion can be tangled filament, printing speed is too high, the temperature is too low. A clogged nozzle or uneven filament diameter can also trigger under-extrusion. (Source)

Solutions and Preventions

Though there are several problems that can cause brittle prints, they can be easily solved so, do not lose hope!

Removing Moisture

If you think your brittle print is due to your filament absorbing moisture, you can easily remove it by throwing your filament in the oven.

You can cook PLA at a temperature of around 40 to 45°C while for, ABS around 80°C is ideal. Placing these in the oven for around 4 to 6 hours can help the moisture evaporate without damaging the filaments. (Source)

Another way to dry your filament is to put them in filament dryers. Dryers like the SUNLU Dry Box and PrintDry are two good options for this solution.

To prevent moisture from seeping in, you can store your filament spools in airtight boxes or bags. Also, it is better to leave in the silica gel that comes with your spool. They help absorb moisture in the packaging.

Maintaining Temperature

If the fluctuating temperature of your surroundings is problematic, a good fix is to have your 3D printer in an enclosure.

Insulated 3D printer enclosures are the best option. They allow temperature regulation with additional perks such as preventing dust collection, reducing toxic emissions, and lowering noise.

You can either make them yourself out of an old cabinet or buy custom ones. To understand more about 3D printer enclosures, read our article, Where To and Not To Place A 3D Printer In Homes And Schools?

Another solution is to simply move to a warmer room, where the cold temperature will not hinder the printing process. But this is not easily manageable for everyone.

Higher-quality Filaments

To avoid buying low-quality filaments, you would have to delve into your savings more. Though they can be somewhat expensive, high-quality filaments are valuable enough to be worth the price.

Popular brands are the way to go to decrease the chances of having brittle prints. Names like HatchBox, PolyMaker, Sunlu among others are credited ‘best 2021 PLA filament brands’ by All3DP.

Here is our selected quality PLA filament to use (Amazon Link)

For ABS, filaments by MakerBot, Ultimaker, PUSH PLASTIC, Octave, etc. are considered the best of 2019 by 3DInsider.

Avoiding Under-extrusion

Filament Width Sensor Prototype Version 3 by Flipper on Thingiverse

To prevent gaps and holes from appearing in your 3D prints, you can regularly clean the printer nozzle – de-clog the nozzle. This helps you make sure that there is not any leftover filament from any of your previous printing sessions.

Buying a filament sensor can also help with the under-extrusion problem. By using real-time width measurement, the 3D printer could compensate for filament width changes as it extrudes.

Summary

If your 3D print comes out weaker and can break easily but just inducing a little pressure. It might be because it is brittle, potentially because of filament moisture, inadequate temperature, poor filament quality, or under-extrusion.

Ways to overcome these problems are:

  • You can remove the moisture from the filament by cooking it in the oven under 40 to 45°C for PLA, and 80°C for ABS. You can use filament dryers to remove the moisture as well.
  • To avoid damp filaments, you can place the spools in airtight containers, and keep silica gels in the bag.
  • You can enclose your 3D printer in an insulated case to control the temperature. Or you can move your printing to a room that is not cold.
  • You can buy higher-quality filaments to decrease the chances of brittle prints. Going for popular brands is a good choice for this problem.
  • Frequently clearing the printer nozzle from leftover filaments can make your 3D printer produce smoother prints.
  • Getting yourself a filament sensor is an excellent investment to ensure your printer recognizes the varying filament diameter and avoids leaving in gaps and holes.

How do I know if my filament needs to be replaced?

When the damp filament is delivered into your printer, its diameter expands and can lead to your printer extruder getting jammed. It can also produce weak and poor-quality 3D parts. This is when your filament needs to be replaced.

Can my printing filament be too dry?

Not really. All you need to do is to take note of the temperature for low-temperature filaments, such as PLA. Generally, most filaments should be dried once, and then stored in an airtight container, or dry box with desiccant.

Preh

A writer and student who is excited to see the 3D printing world evolve and bring the information you crave for it.

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