Traditionally, wax has been the default material used for casting since the Bronze Age. Only recently has resin become a potential substitute for the lost-wax casting method. But can you use 3D printer resin for casting and expect precision, reliability, and safety?
You can use 3D printer resin for casting, but the resin you use matters. You should use castable 3D printer resin that transitions to gas without melting and burns clean without producing ash and residue. Also, the burnout, curing, and washing methods depend on the resin type.
Companies manufacturing 3D printer resin use different compositions, and many ingredients are trade secrets. We don’t know the exact chemical formulas of every composition’s reactions. As I explain in this article, you can use a few types of 3D printer resin for casting reliably and safely.
When Can You Use 3D Printer Resin for Casting?
You are probably familiar with many terms companies use to describe their standard and special 3D printer resin varieties.
The only 3D printer resin among these options that you can assuredly and safely use for casting is the castable variety.
You may also use biocompatible, dental, or engineering 3D printer resin for casting if the liquid resin has identical or similar characteristics as the castable variety you need, but this will always vary by brand.
The casting method and how you intend to use a cast or the specific burnout process must also influence your choice. For instance, some manufacturers, like Formlabs, make castable wax resin, an acrylate photopolymer.
This 3D printer resin combines photopolymerization using SLA or DLP and the lost-wax casting technique involving a low-temperature burnout cycle or process. Still, you may need a compatible 3D printer, resin, and tank or vat for some casting projects.
Bearing all possibilities in mind, here’s how and when you can use 3D printer resin for casting.
What Types of 3D Printer Resin To Use For Casting
You must use a castable 3D printing resin for casting. The most popular castable resins for the lost-wax casting method include those from Formlabs and NovaFab, each requiring different techniques.
Formlabs has at least three types of 3D printer resin for casting:
- Castable Wax
- Castable Wax 40
NovaFab has a range of PowerResins for casting, including the following variants:
Companies like Formlabs and NovaFab manufacture these castable resin varieties specifically for casting, so you can expect a similar experience as you would have with wax. They usually result in a clean, ashless burn with great precision.
However, the specific curing and washing processes vary, and so does the burnout method. You should follow the manufacturer’s instructions in these regards.
Here are a few examples of the differences among the castable resin varieties made by Formlabs and NovaFab:
- You must wash Formlabs Castable Resin with isopropyl alcohol (IPA), but you must use ethyl alcohol to clean NovaFab PowerResins Opaque and Yellow.
- Formlabs recommends a comprehensive curing and washing method for castable resin. NovaFab doesn’t require any extensive post-curing process; only washing is sufficient.
- Also, you can use the standard burnout process for all NovaFab PowerResins varieties. However, the Formlabs Castable Resin comes with a unique recommended burnout schedule.
Formlabs has designed and tested a phased burnout schedule to ensure that its Castable Resin transitions to gas gradually. This process prevents distortion, stretching, and warping.
You May Try Using Clear 3D Printer Resin for Casting
Some people have used standard 3D printer resin for casting with varying degrees of success.
I cannot recommend a typical 3D printer resin for casting without knowing the composition, but a few Formlabs customers have used its Clear Resin for casting.
The main problem with trying any standard 3D printer resin is how the material will burn or melt. Most FormLabs resins resist melting, which may make casting impossible.
Instead, the model or cast will burn before melting if you try to use it. If you want to understand why it’s essential to use castable resin, consider the differences in the compositions of Formlabs Castable and Clear Resin.
Formlabs Castable vs. Clear Resin
Formlabs Castable Resin has bisphenol A dimethacrylate and photoinitiators.
The Clear variety has urethane dimethacrylate, methacrylate monomers, and diphenyl (2,4,6-trimethyl benzoyl) phosphine oxide.
Due to their composition, both these varieties have an initial boiling temperature of over 212 °F (100 °C). Still, only the castable variety has one main ingredient that will melt during the burnout cycle: the bisphenol A dimethacrylate.
The boiling temperature range for bisphenol A dimethacrylate extends to ~853 °F (~456 °C), which is one reason why the Formlabs composition requires the recommended burnout schedule to use up to 1350 °F (732 °C).
The boiling temperature range for the Formlabs Clear Resin composition of urethane dimethacrylate, methacrylate monomers, and diphenyl (2,4,6-trimethyl benzoyl) phosphine oxide may not be suitable for the burnout cycle.
A quick burnout cycle at high heat may lead to a rapid expansion of standard resin. It may not transform into gas cleanly, leaving some ash and other residues and increasing the chances of a rough, bubbly casting.
Therefore, you shouldn’t generalize whenever you consider a particular type of 3D printer resin for casting unless it is a castable variety. Check the composition or consult with the brand to know if the cured and washed resin cast will burn cleanly without ash, residue, or toxic impacts.
When You Should Not Use 3D Printer Resin for Casting
Here are a few scenarios when you should not use 3D printer resin for casting:
- Don’t use standard 3D printer resin or even a castable variety if your final product has to be food-grade or safe.
- Biocompatible, dental, or other certified 3D printer resin varieties aren’t necessarily food safe, so choose your casting projects accordingly.
- You shouldn’t use any standard 3D printer resin variety if the uncured material or a cast in the curing phase requires prolonged handling or skin contact.
- If you aren’t sure whether a 3D printer resin will burn cleanly or turn into a gas without melting, it is better not to use the material for casting.
- Castable resin isn’t necessarily compatible with all 3D printers and components. The Formlabs Castable Resin is compatible with Form 1+ and 2 printers and Form 2 STD and LT tanks. The Castable Wax Resin is compatible with Form 2, 3/3+, 3B/3B+, 3L, and 3BL.
Always test 3D printer resin casts for deformation when subjected to heat before you cast with it. A quick heat test could save your mold from going up in flames.
Also, test your 3D printer resin casts using a lost-wax burnout cycle without any ceramic slurry or precious material to see how it burns. It should be suitable for casting if it turns into a gas without any flames.
If you want to see an example of how to cast with 3D printer resin, check out this tutorial here:
Using 3D printer resin for casting is possible if you use a castable resin. The best way to cast with resin is using the lost wax casting method, in which you melt away the resin after casting. Using this method, you can cast metals with incredible precision and accuracy.