3D prints have many functional uses which can require a good amount of strength to perform properly. Even if you have some aesthetic 3D prints, you’ll still want a certain level of strength so it can hold up well.
I decided to write an article detailing how you can make your 3D printed parts stronger, allowing you to have more confidence in the durability of objects you are making.
Keep on reading through to get some good tips on how to improve and strengthen your 3D prints.
Why Are Your 3D Prints Coming Out Soft, Weak & Brittle?
The main cause of brittle or weak 3D prints is the accumulation of moisture in the filament. Some 3D filaments naturally tend to absorb moisture from the air due to overexposure. Trying to heat filament to a high temperature that has absorbed moisture can cause bubbles and popping, leading to weak extrusion.
What you want to do in this situation is dry your filament. There are a few ways to dry filament effective, the first method being to put your filament spool in an oven at low heat.
You first have to make sure your oven temperature is correctly calibrated with a thermometer because oven temperatures can be quite inaccurate, especially at lower temperatures.
Another more popular method is to use a specialized filament dryer like the SUNLU Filament Dryer from Amazon. Most people who use this are very happy with their results, being able to save filament they thought were no longer effective.
There have been a few mixed reviews though with people saying it doesn’t heat up enough, though these may be faulty units.
One user who 3D prints Nylon, which is notorious for absorbing moisture used the SUNLU Filament Dryer and said his prints are now coming out clean and beautiful.
I’d recommend that you use an extra layer of insulation like a large plastic bag or a cardboard box to retain the heat in.
Other factors that may contribute to a soft, weak, and brittle print is the infill density and wall thickness. I’ll take you through the idea methods to improve strength in your 3D prints below.
How Do You Reinforce & Make 3D Prints Stronger? PLA, ABS, PETG & More
1. Use Stronger Materials
Instead of using materials that are known to be weak in some cases, you can choose to use materials that can hold up well with strong forces or impact.
I’d recommend going with something like Polycarbonate with Carbon Fiber Reinforcement from Amazon.
This filament is gaining plenty of traction in the 3D printing community for providing real strength in 3D prints. It has over 600 ratings and is currently at 4.4/5.0 at the time of writing.
The best thing about this is just how easy it is to print compared to ABS, which is another stronger material that people use.
Another widely used filament that people use for functional 3D prints or for strength in general is OVERTURE PETG 1.75mm Filament, known to be a little stronger than PLA, and still pretty easy to 3D print with.
2. Increase Wall Thickness
One of the best methods to strengthen and reinforce your 3D prints is to increase your wall thickness. The wall thickness is simply how thick the exterior wall of your 3D print is, measured by “Wall Line Count” and “Outer Line Width”.
You don’t want a wall thickness less than 1.2mm. I’d recommend having a minimum wall thickness of 1.6mm, but for more strength, you can definitely go higher.
Increasing wall thickness also has the benefits of improving overhangs as well as making 3D prints more watertight.
3. Increase Infill Density
The infill pattern is the internal structure of the object being printed. The amount of infill you need depends mainly on the object you are creating, but generally speaking, you want an infill of at least 20% for good strength.
If you want to go the extra mile, you can raise it up to 40%+, but there are diminishing returns to increasing infill density.
The more you increase it, the less improvement in strength you’ll get in your 3D printed part. I’d recommend first increasing your wall thickness before increasing infill density so high.
Generally, 3D printer users don’t exceed 40% unless they need some real functionality and the print will be load-bearing.
In many cases, even 10% infill with a Cubic infill pattern works pretty well for strength.
4. Use a Strong Infill Pattern
Using an infill pattern built for strength is a good idea to reinforce your 3D prints and strengthen them. When it comes to strength, people tend to use Grid or the Cubic (Honeycomb) pattern.
The Triangle pattern is really good for strength too, but you will need to have a good top layer thickness to get an even top surface.
Infill patterns work closely with infill density, where some infill patterns at 10% infill density will be much stronger than others. Gyroid is known to perform well at low infill densities, but it isn’t a very strong infill pattern overall.
Gyroid is better for flexible filament and for when you might use dissolvable filament like HIPS.
While you slice your 3D print, you can check out how dense the infill actually is by checking the “Preview” tab.
5. Changing the Orientation (Extrusion Direction)
Simply placing the prints horizontally, diagonally, or vertically on your print bed can change the strength of the prints due to the direction that the 3D prints are created.
Some people have run tests on rectangular 3D prints that are oriented in different directions, and found significant changes in part strength.
It’s mainly to do with the build direction and how 3D prints are built through separate layers that bond together. When a 3D print breaks, it’s usually going to be from a separation of the layer lines.
What you can do is figure out which direction your 3D printed part is going to have the most weight and force behind it, then orient the part to not have layer lines in that same direction, but opposite.
A simple example would be for a shelf bracket, where the force is going to be pointing downwards. 3D-Pros showed how they 3D printed a shelf bracket in two orientations. One failed miserably, while the other stood up strong.
Instead of having the orientation flat on the build plate, you should 3D print the shelf bracket on it’s side, so its layers are built across rather than along the part which has force on it and is more likely to break.
This can be confusing to understand at first, but you can get a better understanding by seeing it visually.
Check the video below for guidance on orienting your 3D prints.
6. Adjust Flow Rate
Adjusting your flow rate slightly is another way to reinforce and strengthen your 3D prints. If you choose to adjust this though, you want to make fairly small changes because you can end up causing under extrusion and over extrusion.
You can adjust the flow for specific parts of your 3D print such as the “Wall Flow” which includes the “Outer Wall Flow” & “Inner Wall Flow”, “Infill Flow”, “Support Flow”, and more.
Though, in most cases, adjusting the flow is a temporary fix for another issue so you would be better to directly increase line width rather than adjust flow rates.
7. Line Width
Cura, which is a popular slicer mentions that adjusting your line width to an even multiple of the layer height of your print can actually make your 3D printed objects stronger.
Try not to adjust Line Width too much, similar to the Flow Rate because it can lead to over and under extrusion again. It’s a good idea to adjust print speed to indirectly adjust the flow and line width to a certain extent.
8. Decrease Print Speed
Using a lower print speed, as mentioned above can increase the strength of 3D prints because it can leave more material behind to fill in any gaps that would occur if the speed was too high.
If you increase your Line Width, you want to also increase Print Speed to keep a more constant Flow Rate. This can also improve print quality when balanced correctly.
If you do decrease your print speed, you may have to decrease your printing temperature to account for the increased period of time your filament will be under heat.
9. Reduce Cooling
Cooling parts too quickly can lead to bad layer adhesion since the heated filament doesn’t have enough time to properly bond with the previous layer.
Depending on what material you are 3D printing, you can try to reduce your cooling fan rate, so your parts can bond together strongly during the printing process.
PLA works best with a fairly strong cooling fan, but can try to balance this with printing temperature, print speed, and flow rate.
10. Use Thicker Layers (Increase Layer Height)
The use of thicker layers leads to better adhesion between layers. Thicker layers will present more gaps between the adjacent parts of the layers. Tests have show that larger layer heights have been observed to produce 3D prints that are stronger.
A layer height of 0.3mm has been shown to out-perform a layer height of 0.1mm in the strength category. Try using a larger layer height if print quality is not essential for the specific 3D print. It is also beneficial because it speeds up printing times.
Check the video below for more details about strength testing for different layer heights.
11. Increase Nozzle Size
Not only can you decrease the printing time of your 3D prints, but you can also increase the strength of your parts by using a larger nozzle diameter like 0.6mm or 0.8mm.
The video below by ModBot goes through the process of just how much faster he could print, as well as the increased strength he got from the increase in layer height.
It’s related to the increased flow rate and increased layer width, leading to a more rigid part. It also improves how smoothly filament can extrude and create better layer adhesion.
Other Things to Try to Strengthen 3D Prints
Annealing 3D Prints
Annealing 3D prints is a heat treatment process of putting 3D printed objects under an increased temperature to strengthen its integrity. With some testing, people have shown increases in strength of 40% according to Fargo 3D Printing’s testing.
You can check out Josef Prusa’s video on annealing, where he tests 4 different materials – PLA, ABS, PETG, ASA to see just what kind of differences occur by annealing.
Electroplating 3D Prints
This practice is becoming more popular because it is practical and affordable. This involves immersing the printing part in a water and metal salt solution. Electric current is then passed through it, thus causing metal cat-ions, like a thin coating, to form around it.
The result is durable and long-lasting 3D prints. The only downside is that many layers may be required if you want a stronger print. Some plating materials include Zinc, Chrome, and Nickel. These three have the most industrial applications.
What this does is simple, to orient the model such that the weakest point, which is the layer boundary is not so exposed. The result is stronger 3D prints.
For more on electroplating 3D prints, check out the video below.
Check out another great video on electroplating, with simple instructions on how to get great finishes on your models.
How To Strengthen Finished 3D Prints: Use of Epoxy Coating
When you are done printing the model, an Epoxy can be applied correctly to strengthen the model after printing. Epoxy, also known as polyepoxide is a functional hardener, used to make your read-made model stronger.
With the aid of a brush, gently apply the epoxy coating to the 3D prints in a way that the epoxy will not drip down. Use smaller brushes for crevices and hard to reach corners so that every part of the exterior is well covered.
A very popular 3D printing epoxy coating that tons of people have had success with is the XTC-3D High Performance Print Coating from Amazon.
It works with all sorts of 3D printed materials like PLA, ABS, SLA prints, as well as even wood, paper and other materials.
A kit of this epoxy is very long-lasting because you don’t need to use much at all to get good results.
Many people say “a little goes a long way”. After the epoxy cures, you get some extra strength and a lovely clear and shiny surface that looks great.
It is a simple thing to do, but if you would like to know more about applying an epoxy coating to 3D prints, check out the video by Matter Hackers.
How to Strengthen Resin 3D Prints
To strengthen resin 3D prints, increase the wall thickness of the model if it’s hollowed out to around 3mm. You can increase durability by adding around 25% flexible resin to the resin vat so it has some flexible strength. Make sure not to over cure the model which can make resin brittle.