The FEP film is a transparent sheet placed in the bottom of the printing VAT between your UV screen and the build plate, that allows the UV rays to enter and cure the resin. With time, the FEP film may get dirty, scratched, cloudy or worse, punctured and you need to replace it.
I wondered just when it should be changed and how often, so I decided to look into it and share what I could find.
FEP films should be replaced when they have major signs of wear and tear such as deep scratches, punctures, and regularly result in failed prints. Some can get at least 20-30 prints, though with proper care, FEP sheets can last several prints without damage.
The quality of your FEP can directly translate to the quality of your resin prints, so it is important to have it in fairly good shape.
A badly maintained or scratched FEP can result in a lot of failed prints and is usually one of the first things you should look at when troubleshooting.
This article will go into some key details on when, and how often to replace your FEP film, as well as some other useful tips to extend the life of your FEP.
When & How Often Should You Replace Your FEP Film?
There are a few conditions and signs that clearly indicate that the FEP (Fluorinated Ethylene Propylene) film may longer work as efficiently as it was working before and you need to replace it for better results. These signs include:
- Deep or severe scratches in the FEP film
- The film has become cloudy or foggy to the extent that you can’t see through it clearly.
- Resultant prints are not sticking to the build plate, though this can be for other reasons
- The FEP film is punctured
You can check whether your FEP film has micro-tears in it by pouring isopropyl alcohol over it, then having a paper towel underneath the sheet. If you notice wet spots on the paper towel, it means your FEP has holes in it.
Water won’t work in this situation due to its surface tension.
Another thing you can do is hold your FEP towards the light and check for scratches and damages.
Look out for bumpy and uneven surfaces.
Not all is lost if you do find holes in your FEP sheet though. You can actually put sellotape over your FEP if it does get a hole that leaks out resin. One user did this and it worked out just fine, though be cautious doing this.
The better you take care of your FEP film, the longer it will last and the more prints you can get. Some users can get around 20 prints before their FEP fails on them. They usually due to being too rough with it, especially with your spatula.
With better care, you should easily be able to get at least 30 prints from a single FEP film, and a lot more after. You’ll know when to replace it, usually being when it looks very poorly, and3D prints just keep on failing.
You can try to get a few more prints from the scratched or cloudy film but the results may not be the most ideal. So, the better option is to get it replaced soon after it shows some pretty bad damage.
FEP film can be damaged more in the middle rather than around the sides, so you can slice your models to print in those lesser-damaged areas to get more use out of it.
If you do come to the conclusion that your FEP film is too damaged to keep on printing with, you can get yourself a replacement from Amazon. Some companies do charge quite a lot for them unnecessarily, so watch out for this.
I’d go with the FYSETC High Strength FEP Film Sheet (200 x 140 0.1mm) from Amazon. It easily fits most resin 3D printers, is perfectly smooth and scratch-free, and gives you a great after-sales guarantee.
Further down the article, I’ll explain tips on prolonging the life of your FEP film.
How Do You Replace FEP Film?
To replace your FEP film, take your resin vat out, safely clean out all the resin then unscrew the FEP film off the metal frames of the resin tank. Carefully place the new FEP between the two metal frames, put the screws in to secure it, cut off the excess FEP, and tighten it to a good level.
This is the simple explanation, but there are more details to know on replacing your FEP properly.
Replacing the FEP film seems difficult, but it isn’t too complicated.
You should take your time and be gentle while performing this job. Just follow the steps as mentioned and you can get it done properly without issues.
The video below by 3DPrintFarm does a great job in taking yo u through the step-by-step process to replace your FEP film properly. I’ll also detail these steps below.
Make sure you are keeping safety in mind when you replace your FEP. Definitely use your nitrile gloves, get transparent safety glasses, and use your mask too. Though once your vat and FEP film are thoroughly clean, you don’t need to use gloves for assembly.
Removing the Old FEP Film
- Take the print VAT and clean it thoroughly with the Isopropyl alcohol or any other washing material, rinse it with water, then dry it.
- Place the print VAT in an upside-down position on a plane table. Remove the screws from the VAT using an Allen wrench or a screwdriver. (Place the screws in a glass or something so that you don’t lose them during the process).
- Pull out the metal frame and the FEP film will easily come out from the printing VAT with this. Get rid of the old FEP film as you won’t need it but make sure that it doesn’t have any uncured resin left behind on it.
- Pick the new FEP film and make sure that you have removed the additional plastic coating on the film that comes with it that protects it from scratches.
- Now clean all disassembled parts of the print VAT to take out all the resin residuals and make it spotless because why not!
Adding the New FEP Film
First, keep this fact in mind that you should not punch a hole for each screw nor cut the sheet to change its size beforehand.
The screw can punch the holes itself or you can do it while the film is correctly positioned on the tank, one at a time. The excess sheet should be cut off after the metal frame is fixed back again.
- Place the tensioner metal frame (not the bottom) upside down on a surface and put a small object with a flat top surface like a Gatorade bottle cap in the middle for tension purposes
- Put the new FEP film on top, making sure it’s even
- Now take the bottom metal frame that have indented holes, and place it on top of the FEP (make sure the small cap is in the middle).
- Hold it in place and once the holes and everything else is properly lined up, use a sharp-pointed item to puncture a corner screw hole
- While holding the frame in place, put the screw in carefully
- Repeat this with the other screws but do it on opposite sides rather than putting the screws in side-by-side.
- Once the screws are in, lay the newly installed FEP film frame back into the resin tank and push it into the tank. The holes with the bevels should be pointed up
- Now with the bigger tensioner screws, put these in fairly loosely, again on opposite sides until they are all in.
- After they are all in, we can start to tighten the FEP film to the proper levels, which I’ll explain in the next section.
- Only after you have tightened it to proper levels should you cut off the excess material
How Do I Tighten My FEP Film?
Tightening the FEP requires you to tighten the screws that hold the FEP film in place. These are usually the larger hex screws at the bottom of your tank.
You want to ensure that you have a good level of tightness in your FEP for a longer print life and for better quality prints overall, with fewer failures. Having an FEP film that’s too loose can also create issues.
In the video above by 3DPrintFarm, he shows a technique of how to test how tight your FEP film should be by using an audio analyzer.
Once you’ve tightened your FEP, turn it on its side and using a blunt plastic object, slowly tap on it to produce a sound like a drum.
You can use an audio analyzer app on your phone to determine the hertz level, which should be anywhere from 275-350hz.
One user had a sound up to 500hz which is far too tight and puts his FEP film at risk.
If you make your FEP too tight, you risk tearing it during a 3D print, which would be a terrible scenario.
When you have tightened it to the proper levels, cut it with a sharp razor, making sure to be careful where your hands are while cutting.
Tips on How to Make Your FEP Film Sheet Last Longer for 3D Printing
- Empty the vat from time to time to give the FEP sheet some space to breathe. Give it a good clean, inspect the sheet to ensure it is in adequate condition, then pour back in your resin as usually
I’d mostly recommend this for larger-scale resin printers like the Anycubic Photon Mono X or the Elegoo Saturn.
- Some people recommend to not clean your FEP sheet with isopropyl alcohol (IPA) because it apparently makes prints adhere to the film more. Others have cleaned their FEP with IPA for months and seem to be printing just fine.
- Don’t put too many heavy objects on your build plate at once as it can create large suction forces which can damage the FEP over time if done regularly.
- I would avoid using water to wash your FEP because water doesn’t react very well with uncured resin
- It may be a good idea to clean it with IPA, dry it, then spray it with a lubricant like PTFE spray.
- Don’t dry your FEP sheet with something that can scratch it, even rough paper towels can cause scratches, so try to use a microfiber cloth.
- Level your build plate regularly and ensure there isn’t hardened resin left over on the build plate which can push into the FEP
- Use proper supports that use rafts underneath as they are good for your FEP
- Keep your vat lubricated, especially when cleaning it out
- Try not to use scrapers to remove your failed prints, rather you can drain the uncured resin from the resin tank and use your fingers (with gloves on) to push the underside of the FEP film to dislodge the print.
- As previously mentioned, sellotape punctures or holes in your FEP to increase its life rather than switching straight away (I haven’t done this before myself so take it with a grain of salt).