How To Make Your 3D Prints Waterproof

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A 3d printed water fountain using white and black PLA filament

3D printing has revolutionized the manufacturing industry, creating complex designs and shapes that were once impossible. Despite the benefits of 3D printing, 3D prints cannot always withstand exposure to water and moisture.

This can be particularly problematic for objects with outdoor applications or used wet environments. If you don’t consider waterproofing your print, it can result in the object becoming weakened, warped, or even unusable over time.

So, how to make your 3D prints waterproof?

Thankfully, there are several methods you can use to waterproof your 3d print, including using the right filament material, slicer settings, and sealing.

We will examine each method’s advantages and disadvantages and provide tips on implementing them effectively to maximize your 3D print’s water resistance.

How To Make Your 3D Prints Waterproof

A 3d printed water fountain using white and black PLA filament
(Source: wirbolwabol via Reddit)

Not all 3D prints are waterproof. If you’re looking to use your prints in and around water, here’s how to make your 3D prints waterproof:

  1. Choose a water-resistant filament like PETG
  2. Print a thick shell
  3. Increase your layer height
  4. Add a slight over-extrusion
  5. Post-process and seal your print

Choose the Most Water Resistant Material

Multicolored filaments of plastic for printing on 3D printer close-up. Spools of 3D printing motley different colors thermoplastic filament. Motley ABS wire plastic for 3d printer. Additive technology

When printing a part that will be exposed to high moisture levels, the first thing to consider is what material is best for the application.

Most of the plastics used for 3D printing are hygroscopic, meaning they absorb water. Not only can wet filament ruin print quality but choosing the wrong filament type can make it more challenging to waterproof your prints.  

When considering water absorptivity, some filament materials soak the water more than others. Choosing the right filament is the first step to waterproofing your 3D prints.

Below are some standard filaments and their waterproof characteristics.

PLA

PLA is notoriously hygroscopic and doesn’t make for the best material if you require your print to be waterproof. While your PLA filament roll will absorb airborne water given enough time, it doesn’t have much of an impact on finished prints as long as the water is cold. PLA has a low melting point compared to other filaments. Although PLA will absorb water, it should be fine for applications that interact with cold water. 

ABS

ABS is an excellent material for waterproof prints. In fact, ABS is commonly used in construction for water pipes and hoses. ABS is a durable plastic but has one major drawback – ABS prints can crack when exposed to cold temperatures. It would be best to use this material in applications where the part is expected to have prolonged contact with warmer water.

PETG

PETG is the best choice for waterproof prints. PETG filament is highly water resistant, though not completely waterproof. This filament also has a higher melting temperature, which can withstand interactions in warm and hot water. The material is also quite stiff, so you don’t have to worry about it deforming under mechanical loads. Generally, PETG is the best choice for printing waterproof objects. And it’s best if it’s combined with the other waterproofing techniques described below.

UV Cured Resin

Resin 3D printing isn’t nearly as popular as FDM printing. But if you’re looking to print waterproof objects, there is no better alternative than SLA, MSLA, or DLP 3D printing. UV-cured resin has waterproof properties and doesn’t absorb moisture. And the printing process ensures virtually no gaps between layers. If you can access a resin printer, this is the best material choice for creating waterproof 3D prints.

Print settings to consider using.

Screenshot of Ultimaker's Cura settings for printing a 3D Benchy with a layer height of 0.12mm

FDM 3D printing objects by printing strings of filament in layers. Unfortunately, 3D printers often leave small gaps between the contours of the layer liens.

Because layer lines aren’t watertight, moisture can seep into the print through the gaps between the layers.

Here are some slicer settings you can use to minimize gaps and other print defects which may affect the waterproofing of the 3D print.

Shells

The shell is the outermost layer of the print that separates the infill from the outside wall. If you want to produce a waterproof 3D print, printing with thick shell walls is best. Thicker shell walls provide a better seal between layer lines and a greater surface area for layer adhesion.

Further, thicker layer lines make it more difficult for water to seep into the 3D print because it has to penetrate further to make it past the shell.

In our experience, a wall thickness of 1.6mm is for applications with minimal contact with water, while 2.4mm is best for waterproof 3D prints.

Layer Heights

Thin layer lines on the left printed at 0.1mm and thick layer lines on the right printed at 0.28mm

Layer lines present the weakest point in the print and are the most susceptible area for water to propagate into the part. 

Printing at a higher layer height reduces the overall number of layers in the print. In other words, when printing with larger layer lines, water has fewer potential points of entry to penetrate the print.

Printing with larger layer lines means your part won’t look as cosmetically appealing as a small slice height would. However, it will help resist moisture.

Extrusion Settings

When considering extrusion settings to use, consider over-extruding the plastic slightly. Adding a slight over-extrusion helps push more material out of the nozzle, reducing the gaps between layer lines and providing a larger surface area for layers to bond.

With this, you will notice an increase in part surface roughness, decreasing the overall print quality. However, adding a slight over-extrusion significantly helps the part resist water.

Post Processing

Woman holding white 3d printed heart. Ideal for diverse concept : love and health, gratitude and charity either technology

Post-processing is one of the most effective solutions for ensuring that your parts don’t leak when exposed to water. With the proper post-process, you can make any 3D print 100% waterproof.

These steps will also improve the surface quality and look of the part. They will further enhance the ability of the part to resist degradation caused by UV light exposure and water resistance.

Step 1: Sand the Part

Sanding your print is a common first step when post-processing 3D prints. Sanding removes all the high points and surface imperfections, allowing the water to bead off the surface rather than attaching itself to the last lines and working through the part.

We generally recommend starting with 80-grit sandpaper and working up to 220-grit sandpaper. If you want a smoother finish, you can increase the sandpaper grit and wet sand the finished part for a mirror finish.

When sanding, ensure you take enough material away to get a smooth surface, but don’t take too much away because your parts may not fit together correctly. If you sand the print too much, you may remove too much material, leaving behind very thin walls which could prevent your waterproofing efforts.

Step 2: Seal the Part

After sanding your print, you still have a bit of a way to go before getting a waterproof finish.

Sealing your print is very important, especially if your part is expected to be exposed to a high moisture level or submerged for a reasonable time.

If your part isn’t expected to come into contact with much water and is used in a more humid environment, you can get away with a simple coat of waterproof paint.

But if you want to build a waterproof object, you’ll want to seal the print for a waterproof finish.

A spray-on lacquer or a spray-on sealer is the best way to ensure your print is waterproof. Begin with a very light coat and allow it to dry before applying two finishing coats to seal the part well.

If you notice some high spots or drip marks, you can always sand them down once the sealer dries.

Is PLA Waterproof?

PLA is one of the cheapest and most popular 3D printing filaments, but it’s not waterproof. PLA is hygroscopic, which means it absorbs water and humidity from the air. When PLA gets wet, it can swell and deform.

Is ABS Waterproof?

ABS is a highly water-resistant filament material used in 3D printing. Though generally water-resistant, it can crack and shrink in cold temperatures, especially when exposed to cold water.

Is PETG Waterproof?

PETG is generally considered to be waterproof and has excellent thermal resistance properties. We recommend using PETG filament in 3D printing applications with high water exposure or when waterproofing is required.

Is UV Resin Waterproof?

UV-cured 3D printing resin is generally waterproof and doesn’t absorb water. The printing process for SLA, MSLA, and DLP resin printing ensures virtually no gaps between layer lines, making it the best material for 3D printing waterproof objects.

Marcello De Lio
Marcello De Lio

Marcello co-founded 3D Print Mentor to share his love of 3D printing. Marcello used to own an online 3D printing company, where he sold unique designs and customized novelty gifts. After closing the business, Marcello’s new passion is 3D printing replica movie props and cosplay items.

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