3D Printing – FEP Maintenance

I’ve mentioned before how fiddly and maintenance-oriented 3D printers can be at times. On of those occasional activities is changing the thin plastic sheet at the bottom of the vat. It’s called the FEP because it’s made from fluorinated ethylene propylene, a highly transparent and low friction material that allows the UV to pass through effectively and help keep parts from sticking to the bottom. This particular polymer is much more commonly known as teflon.

There are a number of failure states, but the most common are physical damage that allow resin to leak and stretching. The leaks can be extremely bad, as splits and tears tend to worsen quickly and can allow resin to get on top of the display or inside the unit and subsequently cure in this places. It can be extremely difficult to clean these things. The stretching is by far the most common, and leads only to print failure instead of equipment damage. A frustrating problem, but not a damaging one.

You can see the sheet on this upside-down vat, mostly because it’s a little bit dirty. Most of them are held on by one or two of these metal rings, which tension the plastic much like a drum. The tightness is actually tested using a spectrogram to see what frequency it vibrates at when struck lightly. The typical target is considered 275-350 Hz.

Most of the tutorials, as well as my own experience, show the method involving two rings screwed together that form a sandwich with the sheet. Apparently Phrozen only uses a single ring, which has some pros and cons, I guess. The upside is there’s a lot less labor involved, with fewer screws and less accessories needed to get the sandwich tension correct. The main con is that it’s nearly impossible for me to get near the traditional target tightness. Without the second ring to provide some initial tension I just couldn’t get there before the main tensioning screws bottomed out.

While I was doing all of these because of print failures due to stretching, there was a spot in one of these that was slightly damaged. It looks like a split in the picture, but it’s actually more of an indention. Probably a spot where I pressed a little too hard trying to remove a failed part. It’s still a good idea to go ahead and replace these due to the failure risk.

If you only own one printer, you can actually buy these in smaller “ready to use” size sheets. Since I have multiples, including a larger printer, it’s actually cheaper and easier for me to order A4-sized sheets and simply cut it in half for the smaller ones. This is usually the cheapest method regardless, but not everyone wants to fool with cutting it. A steel ruler and a hobby knife are all you really need.

It’s also worth mentioning that the sheets shown here still have their protective plastic on, which makes it much easier to see. I don’t know what happens if you forget to peel it off, but it’s probably not anything good.

I managed to get all three of these done. All of them at least tested higher after the change, if not exactly ideal, so that’s and improvement at least. I started a test print on each printer just to see how things would go, but didn’t have time to inspect them closely before I left home. I know both of the small printers had issues, so I may re-level the print bed on each of them and try again.

At the very least, it’s nice to have them running again instead of sitting idle waiting for this.

Y’all take care. Watch out for the adhesive used on teflon coated tape. It’s the only thing I’ve ever seen stick to teflon in any meaningful way.


Hey, it’s Blaugust time! The goal is to simply promote and stimulate the blogging community by encouraging people of all skill levels and backgrounds to post. The official post can be found here and it’s never too late to start.

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