When I got my resin 3D printer, I was excited to try out printing some D&D minis. I got a UV light to post print cure the minis and was excited to try it out. Then I found out an unfortunate truth.
You can over cure your resin 3D print. To avoid over curing keep the print rotating under a UV light with good exposure on all sides for 3 minutes. If you cannot rotate, use a mirrored curing box and time it for 3 minutes. If the print needs more curing, continue exposure for 1-2 additional minutes.
There are several different methods for finishing the curing of your 3D resin print.
Properly Curing Your Print
There are several methods I and other have tried to perfectly finish our resin 3D prints.
The first method I tried was using the sun. This method is kind of hit or miss because so many factors effect how much UV light your prints get exposed to.
The next method I tried was creating a mirrored curing box. This method works really well. Using a mirrored surface inside the box, the UV light can be directed to behind a print an finish curing everywhere but the bottom.
My current process for curing is to use a clear rotating platform the sits under a UV light. I use the Anycubic Wash & Cure Machine but any rotating platform will work.
Using The Sun
The sun, Mother Nature’s UV lamp.
Using the sun to finish curing your print is a simple process. You do have to clean off any excess resin, using either Isopropyl alcohol or another cleaner.
Once the print is dry and there is no cleaner residue, place the print in the sun.
It is very easy to over cure your print using the sun. Not because the sun cures fast but because it cures slow.
Depending on the time of year and time of day, the amount of UV light reaching you can vary dramatically. But compared to other methods of curing, you get significantly lower levels of UV.
Ideally you will want to keep our prints exposed to the sun for about 15 minutes. In Reno, Nevada during the spring time, I found about 15 minutes worked to get a D&D mini adequately cured. Different locations during different times of the year may require more or less time.
While the sun will move around the print, it moves too slowly to get sufficient exposure on all sides. You will need to turn the print around and possible lay it down to get the bottom exposed as well.
This is where you can run into trouble. Once one side has been perfectly cured, when you turn the print around, it is difficult to avoid exposure on the perfectly cured side.
Rather than just sitting the print in the sun, the best technique I have found is to let is cure for 3-4 minutes on one side, then turn it about a quarter of a turn. Let it cure for 3-4 minutes again and turn. Keep repeating this process, including allowing the bottom to get time being exposed.
By turning it as it cures, you can avoid over curing. It just requires keeping a good eye on it as you move it around.
Build A Mirrored Curing Box
Since the process of curing a print in the sun was so time consuming and imprecise, I decided to construct a mirrored curing box.
My UV light source was a Halloween black light that I got off of Amazon. The more powerful the UV light, the faster your prints will cure. If the light is too powerful, you risk over curing.
The black light I got came in a box whose length was slightly smaller than the width. This meant I could turn the light 90 degrees and stick the light into the top of the open box. Your shipping box may be different so you may need to find a box to use.
You can use the box the light came in but any box will work. If the box is larger than the light, you can cut a hole in the closed box large enough to let the light in but small enough that you can set the light on top without it falling in.
Add a reflective surface to the inside of the box using aluminum foil. Crinkle the foil slightly so that it will reflect the UV light in all directions.
The one down fall for this method is that the UV light cannot hit the side of the model that is on the bottom of the box. You will need to move the model around a bit during curing to get every part fully cured. You can use a clear riser like one of these.
Another option is to use one or more UV LED strips like this one on Amazon. Line the inside of your box with these strips on all sides and the bottom for full UV coverage. Again, add in a clear riser and you can get full UV coverage.
Just don’t forget about your models for hours like I have. Set a timer and check the model to avoid over curing.
Rotate Under A UV Light
The Anycubic Wash and Cure Plus includes a large wash basin for cleaning resin off of your prints. It is an all in one machine for any resin 3D printing post processing. It is designed to fit prints for models from the largest consumer resin 3D printers.
If you have a smaller resin 3D printer like a Anycubic Photon or Monoprice Mini SLA, you might be interested in the Anycubic Wash and Cure 2 which is also available through Amazon or Anycubic. This machine is the same as the plus just with a smaller volume designed for smaller resin 3D printers.
For our purpose, we are interested in the rotating platform under a UV light. The Anycubic Wash and Cure Plus includes a top UV light that bends down to increase UV exposure on the top of the print.
In both machines, there is a clear plastic platform that rotates while the UV lights cure your prints. Blow the rotating light there is a reflective surface that helps to reflect the UV light onto the bottom of your print. This ensures full curing for the entire model.
A DIY option is to grab an electric turntable. This turntable is solar powered, just point your UV light so that is hits the power sensor and off you go. Line the turn table with some aluminum foil and place the print on a clear riser to ensure you cure the bottom.
If you go the custom route, be sure to time the curing to ensure you do not over cure.
How Long To Cure Your Print
Each method for post print curing is a bit different in how long to cure. In addition, the resin you use and how much the resin cured during the print also effect how long you will need to continue to cure the print.
Darker resins may require longer cure times. They need time for the UV light to penetrate through the darker pigments.
It is possible that the inside of the print will not be fully cured, no matter how long you cure the outside. This, plus reducing the amount of resin used, is why you should hollow out large models.
As mentioned above, using the sun will take the longest. It is the only method that can vary drastically by day of the year and time of day.
With the sun, gradually turn the print about a quarter of a turn every 3-4 minutes until completely cured.
If you have a light box and use a clear riser, give the print about 3 minutes of exposure. If it is still soft and appears slightly uncured, check it every minute to determine how long it takes to finish curing.
Without the riser, you will want to let it cure for 2 minutes and turn it to expose the bottom and give it about 2 more minutes. Check the print and if it still needs more time, place it back in the light box and move it around every 60 seconds.
If you are using either the Anycubic Wash and Cure or a homemade rotating system, set the timer for 3 minutes. Again, if it needs more time, continue curing in 1 minute increments until the print is completely cured.
Once you have found the best time for your resin, write is down. You now know how much time that resin requires.
When you try new colors or brands of resin, start at the lower curing time and increase in 1 minute increments until cured.
Doing this will decrease the likelihood of over curing.