How to Post-Process SLA/DLP/LCD Printed Objects

To achieve optimal results with your 3D printed material, post-processing is necessary to ensure the object is fully cured and ready to use in your application. If you use a stereolithography (SLA) 3D printer or a digital light processing (DLP) 3D printer, including LCD projectors, post-processing is essential.

When the correct steps are followed, post-processing enables 3D printed objects to reach the optimal material properties, the end product will have the desired characteristics without a sticky surface. Looking to achieve perfect prints? Read our post-processing steps below.

Before Post-Processing: Safety First!

All Garreco Print 3D printable resins and uncured printed objects should always be handled carefully. Using the advised precautions like gloves, glasses, and protective clothing. Regarding gloves, use nitrile gloves or neoprene gloves to protect your hands. Also, be aware that printed parts can leave drops. A paper towel or sheets can be used to catch any drips. Till the last step of post-processing which includes curing in a high-power UV curing box/chamber, the resin is highly sensitive to UV light. The photopolymer resin will polymerize when exposed to UV light, so avoid exposure before post-curing with UV light.

When working with Garreco Print resins, please be advised of the precautionary statements on the resin. Wash thoroughly after handling. If the resin is on your skin, wash it with plenty of water and soap. If the resin is in your eyes, rinse cautiously with water for several minutes. Remove contact lenses if present and easy to do and continue rinsing. Dispose of all safety items that have been in contact with liquid resin as chemical waste. Dispose in accordance with local/regional/national regulations. Avoid release to the environment. When the resin is spilled, please know that after curing, the end product is a polymer and can be treated as polymer waste. Wash contaminated clothing before reuse. Safety Data Sheets (SDS) can be downloaded on each resin page or found on the Support page.

Step 1: Remove the Printed Object

When the 3D printer is finished and the object is printed, the uncured object needs to be removed from the build plate using a blade or other sharp tool. Be careful not to damage the 3D printer or building platform.

Use nitrile or neoprene gloves to protect your hands while removing the object(s) and lay out paper towels or sheets to catch any drips. Do not use water or any cleaner to remove resin from the build platform. A paper towel can be used for cleaning the build plate. For a better cleaning result, 99% Pure Isopropyl Alcohol (we recommend Clean 99) or (Bio) Ethanol can be applied to the paper towel. Be careful not to damage the building platform when cleaning.

Step 2: Cleaning the Object

The uncured printed resin part may have some resin residue on the surface after printing. To have a good end result with your print, cleaning is necessary. If the 3D printed object is not cleaned, the resin on the surface can distort the shape of the model, cured drips can be found and the part can be sticky at the end. To ensure a correct way of cleaning, the advice is to rinse for at least 4 – 5 minutes in 99% Pure Isopropyl Alcohol (we recommend Clean 99) resin cleaner, or (Bio) Ethanol, preferably ultrasonic or under agitation.

When Garreco Print resins are used, it is preferable to use two cleaning containers. The first will be the bath which can remove most of the resin. The second, more clean bath, can be used for optimal cleaning of the uncured object. In this case, the second can be the ultrasonic bath. Make sure that there is enough 99% Pure Isopropyl Alcohol, resin cleaner, or (bio) Ethanol to completely cover the part or change the position of the object and follow the cleaning step again. Uncured printed parts could break or crack if exposed to cleaning solvents for longer than 20 minutes. After this cleaning step, make sure the parts are dry before post-curing. This can be done by placing the part in a well-ventilated area for at least 30 minutes or using pressurized air for 2 minutes.

Please check the cleaning container(s) before cleaning the object. When the cleaning container is very contaminated, this can lead to non-precise surfaces and even surface defects. Also, the end result after all steps can be a sticky object, which is not preferred.

Step 3: Remove the Supports

Because of the cleaning step, the 3D print should have very little to no stickiness left on the surface. Gently remove the supports on the object with a model cutter. The closer to the tips, the easier to remove since the supports are pointed. Cutting supports off too close to the model may remove portions of the model, causing surface pitting.

After post-curing, it is possible that any remains that are left behind from the supports are eliminated by sanding or polishing. Please do not try to sand or polish the object before post-curing. The surface will not be hardened before this last step and therefore the surface is too soft to sand or polish.

Some sources recommend removing the supports after post-curing. One of the advantages is that the object is clean and that no gloves are needed when touching the object. On the other hand, there are also disadvantages. When the supports are removed after post-curing, it is possible to damage the object or take off small divots of material. The supports are harder to remove, which will result in a lot of remaining supports.

Step 4: Post-Cure the Object

The last step includes curing in a high-power UV curing box/chamber for 15 minutes at 65 degrees Celsius. The preferred wavelength of the curing unit should be between 300 – 420 nanometres (nm). The 3D printer curing range of Garreco Print photopolymer resins is between 385 – 420 nm. If a low-power UV curing unit is used, it will need probably a longer curing time and the end result can lead to inferior part properties. The uncured printed object needs to be completely dry before post-curing.

Curing wet and or sticky printed objects can lead to parts with surface defects like a constant sticky surface. With resin cleaner, it is possible to wash with water to remove the resin cleaner. Ensure the object is dry before post-curing in a UV curing box, even when the object is washed with water. After properly post-curing the 3D printed object, it is safe to touch without gloves. When using a UV curing box/chamber especially made for 3D printing, please check the light source and what is possible in terms of temperature control.

Optional Post-Processing

After the four mandatory steps of post-processing, it is possible to improve the aesthetics or function of the part. This optional post-process step includes sanding, polishing, priming, and painting. Keep in mind that these optional post-process steps affect tolerances and details dramatically.

Next Step: Post-Curing

Post-processing is an essential part of resin 3D printing to reach the final photopolymer properties. Printed parts need to be cleaned, dried, and post-cured.