While not as popular as FDM printing due to both the hardware and the material being a lot more expensive in comparison, SLA printing, also known as stereolithography or resin printing, is the go-to choice for printing models with intricate features as smoothly as possible.
Instead of the heat-based approach that we are familiar with in FDM printing, SLA printing technology forms the layers of the model by curing liquid resin with a laser, which allows the printing process to be free of the issues associated with thermal expansion and contraction.
Unfortunately, SLA printing isn’t without problems either, which is why today, we will dive into one of the most common issues of SLA printing, where the UV resin material used for the printing process remains sticky after the curing process that should harden it.
So, what can cause the UV resin to remain sticky after curing?
There are a few different reasons that can cause your UV resin to remain sticky after curing, which we have listed below:
- The UV resin is not clean and dry.
- The wavelength of the UV lamp does not match the curing wavelength range of the UV resin.
- The UV lamp is not strong enough to cure the UV resin in a reasonable amount of time.
- You haven’t waited long enough for the UV resin to completely cure.
- Oxygen inhibition is slowing down or preventing the UV resin from curing.
In the upcoming sections, we will take a closer look at the factors that can cause UV resin to remain sticky after curing, find out what to do to fix this problem, and discuss UV resin-related issues like bubbling, warping, and the UV resin becoming cloudy.
Why Is My UV Resin Sticky After Curing?
While the UV resin should harden after successful curing, it’s possible for the curing process to fail due to various reasons, which will cause the UV resin to stay sticky.
In this section, we will analyze each of the potential reasons behind UV resin remaining sticky after the curing process, which will help identify the cause that’s creating the trouble in your case.
- UV resin is not clean and dry – It’s necessary to wash and thoroughly clean the models printed with UV resin in isopropyl alcohol before moving on to the curing process, as attempting to cure without doing so will cause the UV resin to remain sticky.
- The wavelength of the UV lamp is not compatible – The wavelength of your UV lamp needs to match the required curing wavelength of the UV resin you’re using (which the manufacturer should disclose) for the UV lamp to be able to cure the UV resin successfully.
- The UV lamp is not strong enough – The intensity of the UV lamp determines how quickly it can cure the UV resin, and using a UV lamp that is way too weak can cause the process to take way too long, causing your UV resin to remain sticky.
- Sufficient time has not passed for the UV resin to cure – The amount of time it will take for the UV resin to cure purely depends on the strength of your UV lamp, and as this process is not instant, insufficient time can also be the reason behind your UV resin remaining sticky.
- Oxygen inhibition prevents the UV resin from curing – UV resin being exposed to oxygen reduces the effectiveness of the UV light used for the curing process, which can increase the amount of time required to cure or entirely prevent the UV light from reaching certain parts of the model.
How to Prevent and Fix the Issue of UV Resin Staying Sticky After Curing?
While the quickest way to prevent the issue of UV resin staying sticky is to find the cause creating the problem in your case and apply the appropriate fix, this isn’t always an easy task.
Below, we have compiled a list of solutions to the most common causes behind the issue of UV resin staying sticky after curing, which should help you prevent the problem in the upcoming prints:
- Clean and dry your UV resin with IPA after the printing process. We recommend placing your model in a sealed container of clean isopropyl alcohol for roughly 30 seconds, brushing the tighter areas of the model with a brush dipped in clean isopropyl alcohol, and finally placing the model in another sealed container of clean isopropyl alcohol once more for 30 seconds.
- Use a UV lamp that has enough power and the correct wavelength. We recommend buying a UV lamp that is at least 30 Watts, with a matching wavelength to the requirements of the UV resin you use, which will ensure that you don’t face problems with the UV lamp.
- Give your UV resin more time to cure under UV light. Depending on the size of your model and the strength of your UV lamp, UV resin can take anywhere from as little as 5 minutes to more than 30 minutes.
On the other hand, if you are looking to find out what you can do to fix the sticky UV resin that you already have at hand, here are our recommendations, assuming that you have already washed the UV resin with IPA:
- Cure your UV resin with direct sunlight. While direct sunlight will take much longer to cure your UV resin compared to a UV lamp (hours compared to minutes), it will ensure that your UV resin eventually cures.
- Cure your UV resin in water. Placing the UV resin in water during the curing process is a great way to negate the effects of oxygen inhibition, which can bring successful results when all else fails.
Bubbles in UV Resin After Curing – What to Do?
Another common issue that can arise after curing UV resin is the appearance of air bubbles, which adversely impacts the aesthetic quality of the final product by a considerable margin.
The bubbles that appear after curing in models printed with UV resin are often the air bubbles that have been in the UV resin itself before the printing process has even started due to factors such as pouring too quickly, shaking the bottle too vigorously, and practically anything else that can introduce air bubbles.
Pouring the UV resin slowly, shaking the UV resin bottle more gently, stirring the UV resin inside the vat, and waiting for the air bubbles to dissipate after pouring the UV resin into the vat before moving forward with the printing process can all help eliminate the appearance of bubbles in your UV resin.
Why Is My UV Resin Getting Cloudy?
In some cases, models printed with UV resin have cloudy surfaces instead of the smooth look they should have, which can be a problem if you intend your model to have that particular look.
The cloudiness of your UV resin can be a result of many different factors, such as the quality of the resin, the quality of the 3D printer, the washing process, and the washing material you have used (such as using IPA that you have used before), making it hard to find the real culprit.
The best way to get rid of the cloudiness on the model you have printed with UV resin is to wet sand the model with increasing grits of sandpaper and apply a glossy clear coat (after the curing process is entirely over), which will give your model a clear look without any problems related to cloudiness.
While UV resin staying sticky after the curing process is one of the most common issues in SLA printing, it’s also an issue that is incredibly straightforward to prevent in most scenarios.
Not cleaning and drying the UV resin after the print, using a UV lamp that does not yield the correct wavelength or the intensity, not waiting long enough for the UV resin to cure, and oxygen inhibition can all contribute to the problem of UV resin remaining sticky after curing.
As long as you pay attention to these factors and follow the correct methodology for washing and curing a model that you have printed using UV resin, the UV resin will not stay sticky regardless of the tools you are using for the process.
Mike started his 3D printing journey with the Anet A8 when it first came out back in 2017, and has been obsessed with 3D printers ever since. Nowadays, he primarily uses his Ender 3 to print functional parts that make his life more convenient whenever possible.