July 24, 2018
If you’re used to 3D printing using plastics like PLA, ABS, PETG, or nylons, transitioning to an SLA 3D printer is a foreign experience. While parts of the process are similar, there are some major points that are different between the two, the biggest being safe handling of the materials and maintaining a clean work environment. With plastic based 3D printers, you really only have to worry about hot parts, the occasional fumey material, and throwing away your scraps when your prints are done and supports are removed. With SLA printers, the liquid resins that are hardened to make the 3D prints are a bit more hazardous. Let’s look into how you should be handling your resins, using them before and after cleaning, and how to dispose of them when you’re done with them.
Unlike the plastics used in FFF 3D printing, the resins used in SLA 3D printing are not inert and are actually a skin-irritant in their uncured form. Make sure you have the proper Personal Protective Equipment (PPE) whenever you are working with your SLA 3D printer. In general, nitrile gloves and isopropyl alcohol will have you covered.
Be sure to wear your nitrile gloves anytime you intend to interact with the resins. This includes pouring resin into your vat, handling the build plate before and after printing, cleaning up your printed parts, and disposing of unused resin. Isopropyl alcohol will help clean up any tough spills you have, just be sure to try cleaning it up with soap and warm water first, as isopropyl alcohol can take off the varnish from some surfaces. Try testing it in a hidden spot first before you wipe down your entire counter with what may amount to paint remover.
While you can add more resin to a print while it’s paused so you don’t run out mid print, it’s better to add more resin between prints if you can. Removing the vat, pouring in the resin, and reinserting the vat is safer just in case you spill any it doesn’t end up in the internals of the printer and coats all the boards in a runny, sticky mess of goo. In some cases, it’s unavoidable and you will need to add more into the vat while you have a print running, just because your print consumes an entire vat’s worth of resin. In that case, just be careful and deliberate in how you pour in the resin.
If you’re changing from one color of resin to another, best practice would be waiting until you are completely empty (meaning there is only a shallow pool) of the one color and disposing of the remainder. While not encouraged due to potential cross-contamination, you can get a very fine mesh screen (like you would use for cooking, and specifically polypropylene or stainless steel so it doesn’t react to the resin) and pour the vat back into the bottle to remove any bits of cured resin or failed prints.
Whether it’s an empty resin bottle or a failed print, it is at some level “hazardous waste” and will need to be treated accordingly. The catch all is to cure everything before throwing it away. If you have a failed print, put it in a container and leave it in the sun for a time, then throw it away once it has hardened. If you have an empty container of resin, swish some isopropyl alcohol in it to clean the walls of the container, pour it into a clear contained (glass, plastic, plastic bag) and expose it to UV light until the isopropyl alcohol has evaporated and the resin has hardened, and throw it away.
Basically, if any part of the resin is liquid, you need to dispose of it in a safe way according to your local government regulations. But if it’s already cured and hardened and there is no amount of liquid resin left, you can dispose of it with your normal trash.
The sum of it all is be careful, wear your protective gear, and harden everything before you throw it away.
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