Resin prints go through a lot during the printing process, sometimes needing to be repaired due to leaks, being too brittle and so on. I decided to do some research into the best ways to repair resin prints so you can get better results.
Have a read through this article for important details and methods on how to repair resin prints, as well as how to fix common issues like resin prints leaking, being sticky or tacky, and more.
Why Do Resin 3D Prints Leak/Explode/Pop?
Resin 3D prints can leak or explode due to uncured resin being trapped inside the model. This uncured resin is trapped inside but is still slowly curing and expanding, so it produces extra pressure inside the model until it finally finds a way out. This can either leak, explode, or pop so it can be very dangerous.
Below is an example of resin trapped in the heat of the model, even though I put drain holes in there. This resin is quite viscous and thick so it probably required larger holes, or to put a hole at the bottom of the head to allow resin to pass through the body.
How Do You Fix Resin Prints That Are Leaking or Exploding?
To fix resin prints that are leaking or exploding, first clean up the leaking resin with paper towels and identify where the leak is coming from. There is resin trapped inside so you want to use a small drill and create a hole or two to let that resin drain out. Now use a UV light to cure the inside of the model.
Resin dust is dangerous to inhale so make sure you use a good facemask or respirator to do this, as well as gloves and glasses for proper protection. As you should know, you don’t want to get uncured resin on your skin because it is toxic and actually gets absorbed quickly when skin contact occurs.
If you do get resin on your skin, wash it with soap and water thoroughly.
Hollowed models with infill or several supports inside can trap resin in since it moves very slowly through the model. You want to have at least 2 drain holes in each “locked in” area in your model.
This is referring to areas where they are not connected to other areas of the model, blocked off by the walls. One drain hole allows the resin to drain out, while the other relieves the air pressure, so the liquid can actually move out.
A sign of this happening to your resin prints is when you find small & large cracks in your model. Here’s an example in the early resin printing days.
This model was actually 3D printed around December/January 2020, and it only started cracking maybe 6 months after that, so it really can be a delayed reaction.
I did have holes at the bottom of the model but as you can see, there would have been “locked off” areas where uncured resin could be trapped and slowly curing, build up pressure.
Are Resin Prints Fragile/Brittle?
Resin 3D prints are usually quite fragile or brittle in nature. They can get more fragile for a number of reasons, sometimes due to under exposure or over exposure to UV light. When resin prints are under exposed, it doesn’t harden enough for it to be a strong object, leaving it weaker and more likely to break.
When resin prints are over exposed, the material breaks down and loses flexibility so it is more likely to snap or shatter. You need to figure out the ideal exposure times for your resin and 3D printer for getting the optimal strength out of your models.
I wrote an article you can check out called How to Calibrate Resin 3D Prints – Testing for Resin Exposure, which shows you how to properly calibrate your normal exposure times to reduce fragile and brittle resin 3D prints.
How to Make Resin Prints Stronger & Less Fragile/Brittle
If you find that your resin prints are fragile or brittle, you can try using a resin that is designed to be tough or even flexible so it can withstand more movement and force. These are sometimes advertised as tough or strong resins that have more durable properties.
There are specific resins out there designed to be strong like tough engineering resins. Check out the video below by CNC Kitchen who does some great testing of this type of resin.
Many people who desire stronger prints will mix their normal resin with around 25% of tough or flexible resin to improve strength and impact-resistance.
I’d recommend going with something like the Siraya Tech Tenacious Flexible Resin from Amazon.
You can also go with the Siraya Tech Blu Strong Resin for some serious durability. These resins are a little more premium than usual so it’s good to mix them with your normal resin to balance out the costs and still benefit from their properties.
Another thing you can do to fix resin prints that are weak or fragile is to increase the wall thickness of your prints. If you are hollowing your resin prints as you normally should, you should be setting a wall thickness of at least 2mm to have a decent amount of strength.
You can set 2.5mm or 3mm wall thickness for increased strength, so your prints have some durability.
Sometimes it’s just the design of a model that is weak or fragile, especially if they have thin parts, so you can try printing models that are thicker in design for better strength.
If you have experience editing files, you can actually increase the thickness of parts in a design software.
Why Are My Resin Prints Sticky/Tacky?
Resin 3D prints get sticky or tacky due to the most outer-layer of resin not curing. Oxygen stops the curing process so the resin that is getting hit with oxygen goes through something called oxygen inhibition and isn’t able to cure the outside. Cleaning uncured resin is the main cause of this issue.
Resin leaks can also lead to sticky or tacky resin prints. Most people are surprised how easily resin can stay trapped in a model for, even when there are drain holes in there. A good way to see this is by printing with transparent resin with a hollowed model and looking inside.
How to Fix Resin Prints That Are Sticky or Tacky
To fix resin prints that are sticky or tacky, you want to make sure to clean off as much resin with paper towels as you can before cleaning it. Use a good ultrasonic cleaner or wash & cure station for at least 5 minutes to wash the resin off, then do a further scrubbing with a toothbrush soaked with isopropyl alcohol.
The main thing that creates sticky or tacky resin prints is not cleaning up the uncured resin so make sure your cleaning process is thorough to fix this issue.
Once you do this and cure your model, it should come out non-tacky and smoother to the touch. Some people choose to use an ultrasonic cleaner that has a built-in heater for a better clean.
Also, if your cleaning liquid has been used quite a lot and is really dirty, it may be useful to filter the liquid, put it through a full filtration process, or properly dispose of it and use a new batch of cleaning liquid.
99% isopropyl alcohol is one of the most rigorous cleaners for resin, so if you have something like 70% isopropyl alcohol or a weaker cleaner, it may require more effort to clean the uncured resin off.
I’d recommend going with the Vaxxen 99% Isopropyl Alcohol – Medical Grade, a strong cleaner that you can use to clear up resin from your prints.
Just soaking the 3D model in a cleaning solvent doesn’t get rid of all the excess resin. Toothbrushes help in scrubbing off the excess resin off the prints. You have to get in there and scrub the model with a toothbrush to achieve the best results.
However, be careful not to use a toothbrush with stiff bristles as they can damage the model’s fine details. Instead, use a soft-bristled toothbrush like the Colgate Extra Soft to achieve the best results.
Similar to the above method, you can have a separate container of clean IPA that you use after getting most of the uncured resin off in your primary cleaning method.
A common container people use is the Pickle Jar if you don’t have a very large build volume. It’s a very cheap option and straightforward to use. You can also use a spray bottle or squeeze bottle with IPA and clean the part separately and get into crevices better.
The above techniques should work for prints that have already come off the build plate and have stayed tacky or sticky afterwards.
I did see one user suggest another method which involved brushing UV resin on the part, curing it, then washing it afterwards.
Her technique involves the following steps:
- Get a foam brush, isopropyl alcohol, paper towels, and your UV curing solution
- Get some UV resin on your foam brush either from pouring it into a cup or off your plastic spatula from the resin vat (so it doesn’t contaminate)
- Brush a thin layer of UV resin using your foam brush across the resin print
- Put the resin print in your UV curing solution for 5 minutes+ so it fully cures (it should still be tacky to the touch)
- Now apply isopropyl alcohol to the paper towel and wipe the outer layer of the resin print
- Take the resin print with cured layer and wipe it with a paper towel
- This should remove the stickiness and tackiness from the resin print.
When you do brush the layer of resin on the print, there may be air bubbles present. One user mentioned that they do a quick pass of a heat gun to help remove those bubbles and smooth the resin before curing.
You can get yourself a decent quality heat gun like the Asnish 1800W Heavy Duty Hot Air Gun from Amazon.
Check out the full video below to see this method in action. It could be worth trying if the initial cleaning method doesn’t work for you, but it should work out fine.
Another cool method is curing your resin prints in water trick. As explained above with the oxygen inhibition, water does not carry oxygen like the air so curing your resin prints submerged in water should work well.
I wrote an article about Curing Resin 3D Prints in Water – How to Do It, so check that out for more details.
How Do You Repair Resin Prints?
To repair small imperfections in your resin prints, you can sand the print to smooth over the surface then apply uncured resin directly to the print and cure it. This should fill in any gaps in the model, as well as cracks. You can then sand the repaired area and give it a clean with isopropyl alcohol and a toothbrush.
You can use either a UV lamp or UV flashlight to cure the model.
One way to apply uncured resin to the model is by using a loose support beam and dipping it in resin, then applying it to the model. Another thing you can do is use a dropper to suck up some resin, then apply it to the area, or even use a brush.
The video below shows how the 3DPrintingPro on YouTube repaired their resin model using this technique. Make sure to use gloves for safety while handling uncured resin. Try not to use too much resin and have paper towels ready to wipe up any excess.
You can use this technique to actually stick two resin parts together as well.