Can You Mix 3D Printer Resin? A Quick Guide
Curtis Satterfield, Ph.D.
If you have a few different bottles of printer resin sitting around with only a small bit left in each you may wonder about mixing them. Is it possible or safe to mix different types of 3D printer resin?
You can mix different types of 3D printer resin, but the results can be less than ideal. Mixing resins that are from the same manufacturer and having similar properties has a higher rate of success.
There are several reasons you might what to try mixing resin. The most obvious is using up leftover bottles that don’t have enough resin to fill the printing vat. The second most common reason is attempting to get the benefits of two different resin types in a single print. Finally, you may be trying to get a different color by mixing two or more colored resins in your vat. Whatever your purpose for mixing resin you will need to experiment with different recipes to find what works best for you.
Mixing Resins in 3D Printers
Resin manufacturers discourage the mixing of resin. Looking at this from a skeptical point of view its easy to say that they want to make money by selling more resin. While this may be partially true there is another reason.
Mixing vastly different resin can result in failed prints. The resin manufacturers don’t want you taking to social media complaining about how their resin doesn’t work. They spend large amounts of money on research and development to formulate specific chemistry that results in quality resin. When you start mixing resin types that chemistry is altered. Regardless of if you mention that the failure was from mixing resin, they don’t want their name attached with failure.
Manufacturer’s recommendation aside, it is possible to mix resin types and have good results. For the best chance of success, you should try to mix resins of the same manufacturer. The good news is that chemical composition of resins varies between manufacturer and type, but they still work in the same manner. This similar base formula gives us enough flexibility to mix resins.
Keep in mind that trying to mix vastly different types of resin can result in failure. If this happens you will lose some of your resin as you need to discard the mixed resin. Mixing standard and casting resins together will result in a failed print or the part will not be stable after curing. You need to keep the final properties of the resin in mind when mixing.
If you have several bottles of resin sitting around with only a little bit left in each you might be able to mix them and get one last vat of resin. For example, if you have several bottles of standard resin but they are different colors you could mix them. You can even mix different brands of resin together with success if they are the same type. For most home use resins, companies use the same manufacturers of resin and rebrand the final product. This means that a large portion of resins on the market are chemically similar enough to mix.
You may want to try mixing resin to get different physical properties of a resin. Most standard resins are brittle when cured. By mixing with another type such as flexible resin you can have a strong print with a less brittle nature. Perhaps flexible resin has too much flex for your application. Add some standard resin to the mix to stiffen up your print.
You can mix different resin colors together to get a different color or shade on your print. Want a darker gray? Mix black and grey resins together. You can also mix different transparent resin colors together. Another trick you can try is to add alcohol-based inks to the resin to color it. There also resin coloring kits available to purchase allowing you to dye your resins.
How Resin 3D Printers Work
Unlike fused deposition modeling (FDM) printers where the material starts as a solid, resin printer material starts as a liquid. While the liquid resin is not exposed to UV light it will stay in a liquid state.
The liquid resin used in photocuring resin printers is a mix of chemical monomers and oligomers. When exposed to UV light, the energy from the light causes the monomers and oligomers to cross-link forming polymers. The newly formed polymers are solidified on the body of the 3D print.
To turn the liquid into a solid, the printer uses a UV light source, either a laser or UV LED array, to shine on the resin. Using a laser, the shape of each layer is traced onto the resin causing it to harden. For home use printers, an LCD screen is used to mask out the print layer. The UV light exposes through the clear areas on the screen exposing and hardening the resin. Once a layer has been hardened the build plate raises and the next layer is exposed. This process continues until the entire print is finished.
Once the print is done the model is then removed from the build plate and washed with a solvent to remove and residual resin. The model is then placed in a curing chamber to finish curing the resin. For an overview on how resin 3D printers works check out my article here.
Resin Types and their Properties
When considering mixing resins, it is important to understand the properties of the different 3D resins available.
Standard resin is your basic and usually lowest priced resin. It can come in a variety of colors and is opaque in appearance. Standard resin typically has low viscosity allowing the resin to flow freely during the printing process. Standard resins are designed to reduce part shrinkage when cured. Standard resins also tend to be brittle when cured and may not work well for functional parts requiring high strength.
Transparent resin is another form of standard resin. Transparent resins differ from other standard resin as their appearance is transparent instead of opaque. An interesting aspect of transparent resin is that the UV light can past through the current layer into preceding layers of the print. Because the transparent resin does not absorb the UV light as readily, exposure times for transparent resin tend to be longer. Transparent resin shares the same mechanical characteristics of standard resin.
Casting resin is used in various industries like jewelry making and metal casting. This resin is designed to be “burned out” in a process like lost wax casting. Castable resins tend to be made with waxes that melt when exposed to high temperatures. These resins are designed for this specific purpose and do not work well for other uses.
Tough resin is designed to have higher strength than standard resin. Tough resin is designed to mimic the mechanical characteristics of ABS plastic. Tough resin is ideal for functional prototypes as it produces strong parts that are less likely to shatter. With tough resin you typically need your parts to have a minimum wall thickness. Trying to print models with thin walls can result in failed prints.
Flexible resin is ideal for medical devices, anatomical models, special effects props, and anything that needs to bend and move. The main difference between flexible resin is how much flex the final part has.
Storing Mixed Resins
Once you have mixed resins you don’t want to mix it back in with the original resin. I recommend cleaning out an old resin bottle to store your mixed resin. Be sure to relabel the bottle so that it clearly states what is inside. Include the percentage and each type of resin contained in the mix.
You should also keep notes on the curing times for the mixed resins you have. Because you are altering the chemical make up of the resin, this may affect the exposure times for successful prints. You can even label the exposure times on your mixed bottles as a reminder.
Remember to store your mixed resins like your regular resin. It should be kept in a dark place in a light blocking bottle.
Precautions when mixing resins
It is important to wear personal protective equipment (PPE) when working with resin. Resins are toxic and you should avoid breathing the fumes or getting it on your skin. Always wear an appropriate respirator (Amazon link) and nitrile gloves (Amazon link) while working with resin.