April 16, 2022: NI3DP Part 9 - Changing The FEP Film

Eventually the FEP release film – the clear sheet at the bottom of your resin vat – will go bad. Some people can get a year of regular use out of one sheet of FEP. But if you gouge it with a scraper, or just have a bad day, you'll need to replace it a lot sooner. I got less than two months out of mine, though toward the end it was in heavy use . . . crabs! crabs! crabs! . . . I could have gone a while longer, but I had a run of bad prints and decided to do a full cleanup, including a FEP change.

FEP film is fairly cheap on Amazon; I got five sheets for about 28 bucks.

Get all the resin off the vat – wear your gloves! – and take the vat apart. Mine has no fewer than 28 little screws of three different types. Don't lose any of them. You can use the old FEP film for . . . nothing! Throw it out. Clean the metal parts again once they're separated. There are three metal parts: the vat proper, and the two halves of the resin gasket. Wash the screws with alcohol, too.

(Why are we getting everything so clean at this stage? Among other reasons, because then you won't need your gloves to put it back together.)

If it will make you feel more comfortable, watch a couple of YouTube videos on the subject. Even the one where the guy keeps repeating "eight screws" as he takes out 10 screws. I have had days like that myself.

Remember to take the protective film off both sides of your FEP sheet. Place it on the "bottom" half of the metal resin gasket. Then place the top of the gasket on top of the sheet. You can tell which is the top, because it has 14 conical holes in it to guide the smallest screws. (If you are not using a Mars 3, your mileage will differ on this.)

Punch one hole at a time, as you insert each screw. (If you don't punch a little guide hole, you will go mad trying to get the screw threaded, and if you punch them all at once, one WILL go in the wrong place.)

The first screws (14 on mine) are mounting screws. The next ones are put in from the other side, and these (10 on mine) are tensioning screws. They go through the gasket and into the vat body.

Replace and tighten each set of screws in a star pattern, going diagonally from one side to the other, as though you were putting on a spare tire. (If you have never put on a spare tire, one day you will, and you can replace the nuts in a star pattern as though you were changing FEP film. Knowledge is never wasted.)

Eventually you will get all the screws back in, and the film will be tight and will make a sound like a snaredrum. Tighten and loosen the tensioning screws to achieve this. How do you know when the film is tight enough? The Elegoo documentation with the FEP film just says "not too tight." That is so helpful that I could SPIT. But for $2.95 in the App Store, I got an app called DrumTunerEX. It's not well documented either, but for that price, they're forgiven. At any rate, once you figure out that the HIT! button means hit your drum and not hit the button, you can tune your FEP "snaredrum" to 414 Hz. Then it's tight enough.

The last four screws, the biggest of all, just secure the gasket to the vat body. Yes, three types of screws. Yes, three different Allen wrenches. All in a day's play.

One last point: If this is not play for you, but work – if time is more important to you than money, because you're selling your output and can't afford to be out of production for even a day, or because you've got a deadline before your next big game – consider investing in complete spare resin vats. For the Mars 3, at this writing, I got two for $44 with the FEP already in place and with little covers as a bonus. Then, when your FEP goes bad, you can switch to a whole new vat, and sell your used one to somebody who has more time than money, and everybody wins.

-- Steve Jackson