Using Epoxy with 3D Prints & Casting Small Parts

Using Epoxy with 3D Prints & Casting Small Parts

With an infinite creative potential of 3D printing, the strength, smoothness, or aesthetic finish of the print is generally sufficient to display, prototype, or even functional. This is where the epoxy resin resides, be it a coating to smooth the 3D prints or a casting material to cast very small parts with very direct details.

Here, in this guide, we will investigate the ways in which epoxy is an added value to 3D printing, the workable methods and the best tips to achieve flawless epoxy outcomes.

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What is the reason to mix Epoxy with 3D Prints?

Although 3D printers are accurate, the majority of the printed parts have evident lines of layers, porous surfaces, and insufficient strength. Epoxy addresses these issues by:

• Strengthening → Adding impact resistance and rigidity.
• Smoothing → Filling gaps and layer lines for a professional finish.
• Sealing → Making parts water-resistant or airtight.
• Finishing → Offering a glossy, polished, or pigmented look.
• Casting → Allowing exact replicas of printed models in epoxy or epoxy-based composites.

Two Main Uses of Epoxy in 3D Printing

1. Epoxy Coatings for Prints

Applying epoxy over prints smooths and strengthens the surface. This is especially useful for:

• Cosplay props and helmets
• Display models and prototypes
• Functional parts that need sealing
• Art pieces needing a glass-like finish

Choosing the Right Epoxy

Not all epoxies are equal. In the case of 3D printing consider:

• Low Viscosity Epoxy → Self levelling which is used in coatings which require movement in to layer lines.
• High-Strength Epoxy → Reinforcing mechanical parts.
• Clear Casting Epoxy → Ideal when it comes to producing small transparent items, jewellery or embedded designs.
• Pigmented Epoxy → Provides colour, metallic or pearlsence effects to your components.

Tip: Always check curing time. Epoxies that cure fast can be used on prototypes, but slower-curing resin can give much better results in terms of a clear, bubble-free product.

Step-by-Step: Coating 3D Prints with Epoxy

1. Prepare the Print:

• Rub sand over to smooth.
• Wipe down to get dust out or oils.
• In case of porous filament (such as PLA), before coating, seal with a primer.

2. Mix Epoxy:

• Follow the exact resin-to-hardener ratio.
• Mix slowly to avoid bubbles.

3. Apply Coating:

• Apply a brush or pour-and-flow.
• Turn the piece in order to avoid pooling.

4. Cure Safely:

• Place in a dust-free environment.
• Allow full curing before handling or sanding.

5. Finish:

• Wet-sand for ultra-smooth surfaces.
• Add a final polish or UV-resistant topcoat for long-term protection.

Step-by-Step: Casting Small Parts with Epoxy

1. Design & Print the Master:

• Print in high resolution for fine details.
• Sand and finish the master before mould-making.

2. Make a Mould:

• For one-off use, print a mould directly in flexible filament.
• For repeated use, cast a silicone mould around the 3D print.

3. Mix & Pour Epoxy:

• Degas if possible to reduce bubbles.
• Pour slowly into the mould.
• Add pigments, metallics, or embedded objects for creative effects.

4. Cure & Demould:

• Follow cure times carefully.
• For complex parts, use a mould release spray.

5. Finish:

• Edge sand, polish or apply protective coating where necessary.

Tips for Best Results

• Prevent Yellowing → Epoxy used in parts that are exposed to the sun has to be UV stable.
• Minimise Bubbles → Warm resin a little then mix and pour slowly.
• Layering → To prevent overheating pour in layers on thick areas.
• Colour Effects → Experiment with metallic colour or with clear dyes to give special effects.
• Safety First → Wear gloves, use goggles and work in a well-ventilated place.

Common Applications

• Prototypes → Stronger, client-ready models.
• Miniatures & Figurines → Smooth, painted, and display-quality.
• Jewellery → Cast little charms, pendants or beads.
• Functional Components → Waterproof housings, custom grips or replacement parts.
• Cosplay & Props → Hard-wearing, shiny armour, weapons, and accessories.

Mistakes to Avoid

• Rushing curing times (causes tacky finishes).
• Missing surface prep (epoxy will not stick to greasy/dirty prints very well).
• Application of the incorrect type of epoxy (casting resin and coating resin).
• Pour too thickly (runs the risk of overheating or cracking).

Frequently Asked Questions

Conclusion

Epoxy when used with 3D prints generates new opportunities in terms of power, finishing and creativity. You could be coating props to give them a polished appearance or casting small parts to provide you with a detailed part, epoxy can make you transform an average print into a professional piece.

Experiment, refine, and let epoxy take your 3D prints to the next level.

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