3D printing with resin is a fairly simple process, but there are questions that arise about curing which can get confusing. One of those questions is whether you can over cure your resin 3D prints.
I decided to write an article to help answer this question so you have the proper knowledge.
Yes, you can over cure resin 3D prints especially when using a high-powered UV curing station up close. Parts become more brittle and easily breakable if cured for too long. You know prints have cured when they stop feeling tacky. The average curing time for a resin print is around 3 minutes, longer for larger models.
Keep on reading for more details behind this question, as well as a few more further questions that people have around this topic.
Can You Over Cure Resin 3D Prints?
When you cure a resin 3D print, you are exposing it to UV rays for a period of time, and those UV rays are altering the chemical properties of the photopolymer resin, the same way those UV rays harden the material.
When you have completed a 3D print from a resin printer, you will notice that the print is still soft or tacky. You need to cure the resin to get the print finished properly and to do this you have to expose your print to direct sunlight for UV rays.
Curing or post-curing is important for the resin prints to make it look smooth and to avoid any reactions because the resin can be extremely toxic. Curing will make your print tougher, stronger, and more durable.
Just like curing is essential, preventing your print from over curing is necessary as well. There are many reasons that force us to avoid over curing. The basic reasons are its strength and durability.
No doubt the print will be harder if kept in the UV rays for a relatively long time, but they may become more brittle. It means that the object may become hard to the extent that it may get broken easily.
If you wonder “why are my resin prints so brittle” this may be one of your main issues.
There is a fine balance that you should be aware of, but for the most part, you would have to cure a resin 3D print under powerful UV rays for a long time to over cure it.
Something like leaving your resin print curing overnight in a high-intensity UV curing station is going to really over cure it. Direct sunlight is another factor that can cause over curing unintentionally, so try to keep resin prints out of the sunlight.
It shouldn’t have too much of a negative affect, though if you drop a resin print that is over cured, it’s more likely to break than a resin print that has been cured properly.
If you find that your resin 3D prints are fragile, you can actually add in a tough or flexible resin in addition to your standard resin to increase strength. Many people have gotten great results by doing this.
How Long Do Resin 3D Prints Take to Cure Under UV Light?
A resin 3D print can be cured in a minute or less if it is a miniature, but an average size print normally takes 2 to 5 minutes to cure in a UV rays chamber or lamp. It may take a little longer if cured under direct sunlight.
The time taken to cure the resin depends on the size of the print, the method being used to cure the resin, the type of resin, and the color.
Large resin 3D prints that are made of an opaque material like gray or black are going to require a longer curing time than a clear, miniature 3D print.
While exposing the prints to UV rays or light, it is recommended to rotate the print to change its direction so that it can be evenly cured. This is the reason that the curing station includes rotating plates.
A really effective, yet simple curing station is the Tresbro UV Resin Curing Light with 360° Solar Turntable. It has a UL certified waterproof power supply and a 6W UV resin curing light, with a 60W output effect.
This essentially means it works very well to cure your resin prints quickly. Thin parts of resin can cure even in 10-15 seconds, but your standard thicker parts need that extra time to cure properly.
Another choice that several 3D printer hobbyists swear by is the Anycubic Wash and Cure 2-In-One Machine. Once you remove your print from the build plate, you can wash & cure it all within one machine, very effectively.
It has three main different timers depending on the size of your models, being 2, 4, or 6 minutes long. It has a nice sealed washing container where you can store and reuse your liquid to wash prints.
After this, you place the model on a 360° rotating curing platform where a built-in powerful UV light cures the model with ease. If you’re tired of a messy, tedious process with your resin prints, this is a great way to solve that.
Surface area and volume have a great impact on the time taken by the resin to cure fully. Transparent or clear resin take relatively less time to cure as compared to colored resin because of their different properties.
The UV light can penetrate through these resins a lot easier.
Another factor is what UV strength you are using. When I was looking on Amazon for a UV curing light, I saw some small lights and some huge ones. Those larger resin curing lights use plenty of power, so would require a lot less curing time, probably a minute.
If you choose to cure your resin in the sunlight, something I wouldn’t really advise, it’s hard to determine how long it would take because it depends on the level of UV the sun is providing.
On top of this, your resin 3D prints can warp from the heat which would cause a pretty bad quality model.
You can decrease curing times by increasing the temperature of the environment. UV lights already provide heat from the bulbs, so this helps with curing times.
Can You Cure Resin 3D Prints Without UV Light?
You can cure resin 3D prints using the sunlight, although it is not as effective as a UV light, and can’t be done as practically since the sun isn’t always out.
If you do want to cure a resin 3D print using sunlight, you just have to place the model directly in the sunlight for a good period of time, I’d say at least 15-20 minutes, though it depends on the model size, and type of resin.
Curing prints with the sun through a window isn’t the best idea because the glass can block the UV rays, but not all.
People usually go for UV lamps or UV chambers to cure the resin models. They don’t implement the sunlight method much because it takes far more time as compared to the specially designed cure stations.
UV lamps or UV torches hardly take minutes to cure the resin, all you have to do is to keep the print near to the lights. It is recommended to keep check 3D prints during the curing process as the resin prints are more prone to get over cure under a UV lamp.
Resin prints can also be cured by keeping it in a chamber with a high temperature of almost 25 to 30 degrees Celsius, a heat bulb can be used for this purpose.
It’s possible to cure resin in an oven with the high, dry heat, but I wouldn’t recommend using this method.
Why Is My Resin 3D Print Still Sticky?
If 3D prints remain uncured or have liquid resin on them even after washing with the isopropyl then the prints can be sticky. This is not a major issue because most of the time it can be fixed using simple procedures.
Resin 3D prints can be sticky if the isopropyl is not clean or has dirt in it. Therefore, it is recommended to wash the prints twice in the IPA (Isopropyl Alcohol) and clean the prints with a tissue or towel paper as well.
There are many great cleaners out there, with most people using 99% isopropyl alcohol. Alcohols work great because they are fast-drying and effective at cleaning.
I’d recommend getting the Clean House Labs 1-Gallon 99% Isopropyl Alcohol from Amazon.
The important thing to note here is that while washing the print, there should be two separate containers of IPA. Just wash the print in the first container with IPA which will wipe out most of the liquid resin.
After that go for the second container and shake the print in IPA to remove the remaining resin completely from the prints.
When it comes to curing the sticky prints one of the most common and easy to implement solutions is to keep the print a bit more time under the UV rays and then sand the print properly.
Sanding is an efficient, effective, and inexpensive technique that is used to provide a smooth finish to the 3D prints. These procedures can cure the sticky or tacky parts of the 3D prints.