Sometimes things go wrong. Your car doesn’t start in the morning. Your boss yells at you about your TPS reports. Your roommate eats the last Oreo even though your name was on the package and he knew you were saving it (I have not forgiven this transgression).
And sometimes your printer’s FEP pops a hole and spills resin on the screen.
I recently had to deal with several small hills of resin on my printer’s screen due to a pinhole in my FEP. Hopefully my first experience leaves you more prepared than I was.
What is a FEP?
A FEP (Flourinated Ethylene Propylene) is a plastic film that sits at the bottom of your resin vat. This film acts a barrier between your liquid resin and the curing source (your screen). FEP film is used in 3d printing because it has good chemical resistant properties, and generally won’t adhere to your print.
How did this happen?
That’s a great question! Unfortunately, I don’t have an answer.
If you have a print fail you need to empty out your vat, pouring the resin back into the bottle through a sieve to make sure that you are catching any larger hardened pieces that may be present. If your printer has a self-clean function (where it exposes the FEP to a solid block of UV light) you should do this to cure the bottom layer of resin. This traps any floaters against the FEP and allows you to be sure that when you pour out the resin and peel the clean layer away you are left with a pristine tank.
But, as I said above, sometimes things go wrong. In my case, I didn’t have a print failure that I can blame. Everything was going well until it wasn’t. If you are working with poorly supported models you could potentially have pieces of resin break off from the model and start to float around the tank. If one of these floaters gets in the wrong place it will be pushed down into your FEP. This could potentially puncture your FEP, or worse, break your screen.
Protecting the Screen
The best maintenance is preventative. If you address a problem before the machine breaks you are ultimately saving yourself some pain and money.
In the case of your screen, the easiest way to protect it is to get a screen protector (who saw that coming?). These only cost a few dollars and make cleaning up resin spills much easier. Simply peel the screen protector off and dispose of it.
They also provide a buffer for your screen to keep the screen from cracking. Most modern printers arrive from the factory with a screen protector installed, but you should still verify that one is there if you are in doubt.
The one point to note: if you do not currently have a screen protector, and you are installing one on your printer, you may want to recalibrate. The screen protector will not make a huge difference, but it is an extra layer of material that your UV light must pass through.
If you don’t have a screen protector you might be in a tight spot if you have a resin spill. There are a couple methods of cleaning cured resin off your screen, and I’ll link them below. Full disclosure: I have not tried either of these methods, so I cannot personally speak to their use.
Replacing the FEP
Your FEP should be considered a consumable part of your printer. Resin, gloves, and paper towels need to be replaced more often, but if your FEP becomes cloudy or gets punctured then the only fix is to replace it.
I have an after-market resin vat from Sovol that has been wonderful to use. I also found out that it has significantly fewer screws holding the FEP in place and still doesn’t leak. There are still a lot of screws used in the process of holding everything in place, and making sure you are balancing your frame while replacing it is important to avoid slack in the FEP.
Once the screws are pulled out, you can dispose of the old FEP, and lay the new one in place. You’ll need to have a hobby knife or sharp tweezers on hand before replacing the screws. Machine screws don’t have sharp points, so you will need to puncture the screw-holes in the FEP before you can get the threads of the screw to make contact with the threads of the hole. The FEP will have some excess material around the edges, but that’s a good sign, since it means that you have less risk of a bad seal. You simply need to take a hobby knife and carefully cut around the edge of the vat to remove the excess.
Once that new FEP is in place it should be drum-head tight. The video below shows some light taps so I could test the tension.
Preventative maintenance and a solid plan for accidents are the best steps to achieve worry-free printing. When those accidents happen: don’t panic! It’s all part of the fun of the hobby. The more you work with your printer the more intimate you will become with it, and the more you will be able to get out of your little box-shaped friend.
Happy printing, friends!