Kapton forming bubbles under print

I have an 8" x 8" piece of 2 mil Kapton on top of my aluminum bed plate. I applied it with zero bubbles not using a soapy solution. Starting out with a corner and keeping tight enough tension while peeling back the backing worked amazingly well. I am printing PETG starting with 75C on the first layer and then dropping to 60C for the rest of the print. The particular filament that I have prints at 260C. It sticks great and comes off fairly easily after the print and bed cool to room temperature. The problem I am having is that when I remove the print the outline of the print is one giant air bubble. Using a credit card, I am able to smooth out most of it except for a bubble or a few. To get those out, I have to use a needle to pop the bubble and then smooth it out with the credit card. This is becoming a paint in the ass. Is there any way to avoid this? Or is this just a problem with Kapton either stretching when hot or having a shitty glue? I've thought about printing directly on glass or getting a sheet of PEI to print on. Thanks for your help.

Do any bubbles form under the kapton if you just heat up the bed?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Quote
the_digital_dentist
Do any bubbles form under the kapton if you just heat up the bed?

None. Only when I remove the part.

How are you removing the prints?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Quote
the_digital_dentist
How are you removing the prints?

I wait until the print gets to room temperature. They come off fairly easy. If it's a taller part I loosen one corner by hand and then use a flexible spatula (drywall kind) to pop it off. If the part is smaller and hard to grip, I will get a corner lifted with the spatula or a razor blade and then pop the rest off with the spatula.

Edited 1 time(s). Last edit at 03/12/2016 02:46PM by mlaustin66.

Hmmmm. It sound like the kapton is a bit stretchy and maybe the adhesive on it isn't very good. In order for bubbles to form under it when removing a part there would have to be a hole in the film that lets air get under it, maybe the holes you made in trying to remove bubbles. Try replacing it using the soapy water technique and push the bubbles out from under it as you go, then heat it up to about 50C and push out any more bubbles that form. Let it sit and cook for a while- I think 2 mil kapton is thin enough that any remaining air trapped in bubbles will diffuse through the film. Try not to poke holes in it...

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

The bubbles formed on a new sheet. And I tried to print other prints in different spots on the Kapton before doing any popping. All new spots I tested did the same thing. In order to get the bubbles out, I had to use the needle. There were absolutely no bubble under it when first applied. I tried the wet method and still had the same issue. Perhaps I will try applying a new sheet with the bed warm.

Applying big sheets is tough because it's hard to push bubbles from the center all the way to the edges of the film. I use 2" wide tape so I never have to push bubbles more than 1" to get rid of them. Using tape also means that when the center gets damaged I can just replace the center strips of tape without replacing the entire bed covering. I use 5 mil tape and it doesn't stretch and takes a lot of abuse before it gets damaged to the point where I have to replace any of it.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

So I fixed this problem. I had the first layer temp at 75C and the rest at 60C. It was cooling to quick in relation to the plastic I suppose, and bubbles were forming. I switched it to 75C for the whole print, and now I don't get bubbles. I get an outline of the print that goes away after rubbing my finger across it. Thanks for all the responses.

So the fix did not work. In finding a thread with a similar problem, it seems that the PETG sticks too well to the Kapton tape. So after repeated removals it causes the tape to slightly lift each time and ultimately forms air bubbles. I switched to glass and hairspray for now, and that seems to work well.

Hey, the issue isn't solved yet. I have the same problem, aluminium plate, and kapton, applied in the Craftunique factory bubble-freely. With pla I didn't have any problem, but nylon warped off, so I started using glue stick, then I started getting the bubbles under every second print on the given surface area. I suspect that the adhesive under the kapton vaporises and cannot get back into normal state.