How to Make 3D Prints Watertight: 5 Simple Steps

Who among us hasn’t fired up their 3D printer, crafted a beautiful cup in vase mode, and then filled it with water, only to be dismayed by leaks? Many individuals encounter this issue during their initial forays into 3D printing, and fortunately, there are several straightforward steps to prevent such incidents.

Whether you’re creating a container for food, a vase for flowers, a water pump, or an accessory for your fish tank, it’s crucial that your 3D-printed objects effectively prevent liquids from entering or escaping. This article explores various methods to achieve watertight FDM 3D prints, encompassing design choices, water-resistant materials, post-processing techniques, and more. It guides you through the process of ensuring your 3D printed items are prepared for any scenario, whether you intend them to contain a substantial amount of liquid or just a small quantity.

In the context of this article, watertight 3D prints are defined as those designed to be impermeable. When seeking professional 3D printing services, it’s essential to consider the intricacies of achieving watertight results in your prints.

Making Watertight Prints

What does it mean to produce watertight 3D prints? Initially, let’s clarify some terminology. It’s essential to understand that being waterproof is not synonymous with being watertight, despite the frequent interchangeability of these terms.

In the context of 3D print service in Malaysia, “watertight” implies that a container or vessel is designed and printed in a manner that prevents water from entering or escaping. This entails ensuring that a container does not exhibit leaks or allow liquids to pass through, even when submerged, holding liquids, or exposed to heavy rainfall.

On the other hand, “waterproof” signifies that a material or object effectively keeps water out. The material acts as a barrier, preventing water from infiltrating, and the object remains unaffected by splashes or excessive moisture. However, a waterproof object might still possess gaps, seams, or openings that permit water flow if submerged or subjected to water for an extended duration.

Consider a phone case as an example. Many protective cases, crafted from materials like high-density, vacuum-formed plastic, and glass, excel at keeping water out. These cases can even shield your phone from splashes or drips to some extent. Nevertheless, most phone cases cannot be deemed watertight because they feature gaps, ports, or other openings through which water can pass. To achieve watertightness, the phone case would need to cover or seal every entry point against fluids.

Safety Considerations

Before we proceed, it’s important to consider some safety aspects. Depending on the intended use of the 3D printed container, additional safety measures may be necessary. If the container is meant to hold food or beverages, considerations related to food safety become crucial.

The layer-by-layer construction inherent in FDM printing imparts a porous nature to the prints, potentially allowing water to seep through. This porosity poses a significant concern for food safety, as the voids provide a breeding ground for harmful bacteria, even if the object appears watertight on the surface. Therefore, achieving the highest possible printing accuracy is essential to minimize voids in 3D-printed objects intended for contact with food and drinks.

Furthermore, the use of food-safe filaments is crucial. Most filaments are not suitable for food contact, as they may degrade and release harmful chemicals. It is advisable to opt for filaments explicitly labeled as food-safe to ensure the suitability of 3D-printed objects for applications involving food contact.

Beyond dishes and flower pots, containers like air tanks and fuel containers also require watertightness. For safety reasons, containers under pressure or containing volatile liquids should undergo additional testing before use. While it might be technically feasible to 3D print a fuel tank for an RC car, caution is warranted. Such tanks typically consist of high-density polyethylene and may involve additional materials like ethyl vinyl alcohol, which may not be readily available to most home enthusiasts. Containers intended for fuel or other hazardous contents are typically constructed from aluminum or steel to mitigate the risk of rupture or leaks.

How To Do It?

The ensuing sections will guide you through five simple measures to ensure that your prints are impenetrable.

1. Design for Water Tightness

The initial step involves designing models optimized for watertightness. 3D printing provides extensive design possibilities, allowing the creation of various containers or vessels. However, for optimal watertightness, it is advisable to opt for simpler designs.

Designs featuring numerous right angles, sharp corners, and overhangs are more prone to permeability. Conversely, designs with smooth curves and minimal hard angles are easier to make watertight. This is influenced by the filament’s deposition geometry, where each corner or change in direction during the print path presents an opportunity for gaps to form.

Designs incorporating compartments within the container’s interior spaces pose additional challenges for achieving watertightness. The difficulty increases with every change in direction or movement within a layer, as dictated by the printhead.

Consider a basic bowl, which, although not a sealed container, is predominantly curved with few hard angles. The printhead’s movement remains relatively smooth, creating fewer opportunities for gaps, holes, or pockets that could allow water seepage.

In contrast, an open-top cube container features intersecting 90-degree angles, where corners converge to a point, resulting in sudden changes in the printhead’s direction and potential lifting during the printing process. While design choices are rarely as straightforward as a bowl or a cube, these examples illustrate simplified potential issues. As a general rule, less complex designs are easier to make watertight.

2. Choose an Appropriate Material

The second step involves selecting a suitable material, with polypropylene (PP) being an excellent choice for watertight prints. Despite being less renowned than other materials, PP possesses inherent hydrophobic properties, effectively repelling water, and showcases good chemical and impact resistance. These qualities make it a reliable option for creating durable and watertight parts.

ABS, PETG, and ASA are popular materials that serve as decent options for watertight prints. While ABS and PETG are known for being more challenging to print than PLA, proper settings and adherence to design considerations should mitigate any obstacles in creating watertight prints.

Conversely, some materials are ill-suited for crafting watertight 3D prints. PLA, despite its popularity and ease of printing, is unsuitable for hot liquids due to its low melting point. Moreover, it may not be the optimal choice for long-lasting watertight prints as it can swell over time.

Nylon is another material to avoid. Although versatile and durable, making it ideal for functional parts, certain compositions are unsuitable for wet environments as their polymer chains can break down when exposed to water.

3. Adjust Your Slicer Settings

The next step involves adjusting your slicer settings, providing one of the quickest ways to achieve a watertight print. However, it’s not as simple as increasing temperatures and slowing speeds.

The settings you tweak will depend on your material choice, printer setup, and even the design. While no single setting guarantees a watertight print, collectively, they can bring you a step closer. Let’s take a look!

Nozzle

Although not a setting per se, your nozzle size significantly impacts an object’s watertightness. While 0.4 mm is the standard, using a 0.6 mm or wider diameter may yield better results by increasing the flow rate and reducing space between layers. It’s worth noting that printing with thicker layers becomes practical when using wider nozzles, as larger nozzles necessitate a higher minimum layer height, reducing potential gaps.

Layer Height

Counterintuitively, when using standard 0.4-mm nozzles, it’s recommended to print with a 0.15-mm layer height. Watertight qualities are optimal at the lowest layer heights (0.05 mm) and decrease at the highest layer heights (0.3 mm) with a 0.4-mm nozzle. Seams and transitions between solid infill and perimeters are the primary sources of leakage, rather than contact between layers.

Perimeters

In general, a higher number of perimeters increases the likelihood of a watertight print. Additional perimeters reduce the chance that water will have a direct path through existing barriers. The subsequent perimeter acts as a backup to seal small gaps that may have developed in an outer perimeter due to under-extrusion, seams, or other issues. While some materials like ABS may suffice with two to three perimeters, others like PETG and PLA perform better with four or more perimeters. Typically, a perimeter count above three is a reasonable starting point.

Seams

The visible seam running vertically (Z-axis) on a 3D printed object is known as the “Z seam” in 3D printing. It results from layering, where the material is continuously deposited along the Z-axis as the printer progresses from one layer to the next. Z seam placement is crucial, influencing both the final print’s appearance and watertightness. Adjusting this setting in your slicer can align or randomize these gaps in your print. If significant gaps appear at the Z seam, modify your retraction settings to prevent voids.

Infill

Higher infill density translates to fewer gaps in your model. While the instinct might be to make the infill solid, improper adjustments in other settings could still lead to leaks. Ideally, no water should enter the infill areas, as it can cause additional issues. For prints under pressure, consider increasing infill density to 40–100% to enhance structural strength.

Extrusion

Gaps in parts can result from under-extrusion, a common issue even in well-tuned print profiles prioritizing factors like dimensional accuracy, structural strength, or cosmetic consistency. Slightly increasing the flow rate can alleviate under-extrusion. Begin with 102% and incrementally adjust until improvements plateau.

Temperature

Enhancing layer adhesion can prevent gaps by printing at a higher temperature. It’s advisable to print at the maximum temperature your material can withstand. However, caution is necessary to avoid material boiling, leading to additional problems and potential holes. Incrementally raise the temperature by 5 degrees until finding the optimal level.

Speed

Reducing print speed settings, particularly in areas like perimeters and top/bottom layers, significantly improves the likelihood of a watertight print. The extent of speed reduction depends on factors such as the printer, material, slicer, and firmware. Slightly lowering print speed enhances adhesion and addresses common small gaps in FDM printing.

Cooling

Adjustments to cooling or fan speed settings in your slicer can substantially impact the appearance, strength, and watertightness of your print. Consider reducing cooling by several percentage points to extend the time the filament stays molten, potentially improving layer adhesion and preventing leaks.

4. Post-process Prints

For the item to become waterproof after printing, more post-processing will probably be required. There are numerous post-processing techniques that might offer the answer you need. Let’s investigate a few of the most well-liked ones.

Vapor Smoothing

Vapor smoothing is a post-processing technique that enhances the surface of 3D printed objects, particularly ABS prints, by immersing the object in an acetone bath or vapor chamber. This method involves heating the material, causing it to flow and eliminate roughness, resulting in a glossy, polished finish that can potentially seal gaps and enhance watertightness.

Temperature Treatment

An alternative method to achieve water tightness involves heating the completed print to eliminate gaps and encourage bonding between layer lines. This heating process is commonly carried out in an oven or heated chamber, aiming to heat the object enough for layers to seal without causing deformation or melting of the print.

While challenging and not always the most effective, some may attempt this method using a heat gun, although results can vary.

Surface Coatings

The application of surface coatings is a straightforward way to achieve watertightness, with the key being the selection of the appropriate coating. Painting prints with acrylic or enamel paint proves effective due to their durability and solvent-based composition.

For those who prefer to skip the paintbrush, spray paint is a viable option. Acrylic spray, a protective coating designed to seal and finish various surfaces, including 3D printed objects, consists of a fast-drying, water-based acrylic polymer, delivering a clear and durable finish. Most spray paints are tinted acrylic-based paints, allowing simultaneous sealing and coloring. Simply spray the model inside and outside multiple times, allowing it to dry.

Some surface coatings that you might not have thought about yet are listed below.

Epoxy

Epoxy, a polymer commonly utilized in adhesives, coatings, and composite materials, consists of two primary components: an epoxide resin and a hardener. When combined, these components create a sturdy, rigid material with strong adhesion and excellent resistance to chemicals and water. Although applying epoxy to a 3D printed vessel is labor-intensive, messy, and time-consuming, it is one of the few methods suitable for food-grade use, providing excellent results when executed correctly.

Glues

Various glues can serve as a watertight layer for a 3D printed container, especially popular for creating leak-proof plant pots. Wood glues from reputable brands, particularly those tested for marine or wet environments, are commonly employed. The glue is typically applied in multiple layers and allowed to fully harden before use. Some glues are even deemed safe for use near food.

Wax

Waxes like candle wax, beeswax, and surfboard wax can be rubbed onto a print to fill small pores or gaps in the surface. Alternatively, the wax can be melted and either painted or dipped directly onto the object. While beeswax is a popular choice for health and safety considerations, it’s important to note that wax has a low melting point, and its effectiveness may diminish on warm days.

Nail Polish

Nail polish, surprisingly, can be used to create a protective coating that adds some level of watertightness. While easily accessible, it has some drawbacks, including the inconvenience of application due to its small brushes and bottles. Additionally, it tends to be relatively expensive, making it more suitable for smaller prints.

Plastic Dips

Liquid rubberized plastic coatings, when brushed or sprayed onto the surface of a 3D printed object or used as a dip, can provide a layer of watertight protection. This coating not only makes the print watertight but also enhances its grip, making it easier to handle and protecting it from damage. However, it’s essential to note that many of these plastic dips are considered toxic in their liquid form.

5. Test Prints

The ultimate step in achieving a watertight 3D print involves testing its effectiveness. To conduct a proper test, fill the 3D print with water and allow it to sit for at least an hour before scrutinizing for potential leaks.

For a comprehensive assessment, it’s advisable to subject the print to diverse conditions, such as varying water levels or employing different types of water like saltwater and freshwater, ensuring its functionality in the intended environment. If the print remains leak-free with cold water, proceed to test it with warm water. Repeat these testing procedures several times, pausing between each attempt. This iterative process helps instill confidence in the print’s watertight capabilities or highlights areas that require further attention.

In scenarios where the container needs to remain dry while submerged, alter the testing method accordingly. Instead of filling it with water, submerge the vessel to the intended depth, allowing it to remain submerged for a minimum of an hour before checking for any signs of leakage. This meticulous testing approach enables the identification and resolution of potential issues before the object is put into practical use.

It’s essential to acknowledge that even a seemingly watertight container may experience leakage over time due to swelling induced by water absorption. For instance, prolonged contact with water might cause sections of a PLA print to swell. Although this swelling could lead to deformation or even fractures in the print, it won’t result in complete deterioration. The extent of swelling is contingent on the filament material and will eventually reach a saturation point, ceasing further expansion.

Final Thoughts

In conclusion, it’s crucial to understand that there is no universal solution when it comes to creating watertight 3D prints. The chosen method’s efficacy depends on factors such as material selection and the intricacies of the design itself.

While adjusting print speeds and elevating hot end temperatures can serve as a promising starting point, it’s imperative to recognize that these measures don’t represent the sole recipe for achieving a flawless watertight print. The journey towards waterproof prints involves making informed decisions regarding design elements, material choices, slicer settings, and the incorporation of post-processing techniques.

Some may argue that FDM printing is inherently unsuitable for producing watertight objects. Nevertheless, the resilient and inventive nature of the printing community consistently demonstrates that, with determination and creativity, any printing challenge can be overcome.

Collaborating with reputable 3D printing websites Malaysia or Malaysia 3D print service providers can offer valuable expertise and assistance in producing high-quality, impermeable 3D prints for various applications.

Contact us today to embark on your journey towards watertight prints or explore our 3D printing services.

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