Tips and Tricks: Things You May Not Know About SLA/DLP/LCD Resin

As we all know, SLA/DLP/LCD parts are finished because of stereolithography technology. And the most important material for SLA/DLP/LCD 3D printing is UV curable resin/ photosensitive resin. Frankly, resin is not easy to get along with. It has its temper so it requires great care to keep it “alive” and handle it. Do not assume that you know them better. Here are the tips and tricks to help you know more about SLA/DLP/LCD resin.

How to store SLA/DLP/LCD UV curable resin?

• Keep UV curable resins sealed tightly in their containers, out of direct sunlight and within the temperature range suggested by the manufacturer.
• A small headspace of air is needed to keep the resin from gelling. Do not fill resin containers to the top of the opening.
• Do not pour used, uncured resin back into new resin bottles.
• For long-term storage, pour resin into a separate, opaque container from the resin tank.
• Do not store uncured resin in refrigerators used for food and beverage storage.

Why is Post-Curing needed for SLA/DLP/LCD parts?

Though the parts have reached their final form, you can easily detect that the surface of the part is still tacky and relatively soft. They are not fully reacted and cured out of the printer so post-curing completes any unfinished reactions. This is much of the reason for the changes in aesthetic and mechanical properties.

Material properties, such as modulus, strength and stability will be improved by UV post-curing. The surface of post-cured parts are tougher and drier which makes them easier to sand and paint.

What will happen with over-curing?

Material will degrade due to UV irradiation. Most organic materials are damaged by UV exposure. With extreme levels of UV exposure, the part will degrade and this is why ‘over-curing’ will cause brittleness. Placing a part outside is generally not nearly enough to cause any notable amount of degradation. But curing a part over night in a high intensity UV chamber might be enough to damage the material. This is not unique to resin and would occur in most organic materials.

Will curing prints under water speed up the curing time?

Yes. Water does absorb UV light, the absorption is not significant at the wavelengths used to cure UV resin. In addition, underwater heat dissipation and diffuse scattering effect will be better. So you don’t have to add much exposure time if you cure your parts in a shallow tank of water. There are really no “cons” to curing in a water bath, other than getting your parts wet and require drying.

Is post-curing with sunlight useful?

If you don’t have a UV chamber, You can submerge the print in a clear container filled with water. Then place the container under direct sunlight. Of course, the exposure time will be much longer than under direct UV lamp. If the print still feels uncured or sticky, leave the print and the container in the sun for some more time.