PETG bonds to PEI like superglue!

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shinigami
Posts: 9
Joined: Sat Apr 23, 2016 10:21 pm

PETG bonds to PEI like superglue!

Post by shinigami » Mon Jan 20, 2020 9:41 pm

Hi,

I use to have problems with prints warping when printing on Kapton tape or glass. I tried hairspray and Elmers glue on glass, which improved the situation, but still allowed some warping. About a month ago I switched to PEI; I purchased a sheet of PEI, cut it to 8x10 and used the double sided tape they include to attach to to the MakerGear glass bed. Once I did that, PLA printed perfect with zero warping no matter how big the object. However, now I have a new problem: PETG bonds to it so strong that it's impossible to remove without damaging the printed object. In some cases, I've actually torn apart the print when trying to remove it off the PEI sheet. PETG is practically impossible to remove off the PEI sheet.

I've tried suggestions I have seen online: 1) remove the print before the bed cools; 2) reheat the bed to 60 - 80 C; 3) squirt some isopropyl alcohol around the edges before prying off the object; but none have worked. I use PLA for prototyping and PETG for final printing and I am desperately trying to find a way to get it to work. I do not want to give up the perfectly flat prints I get with PEI but I also don't want to destroy the plate trying to remove the object. I've seen suggestions online of using Windex or Elmer's glue to weaken the bonding between PEI and PETG but I am reluctant to go down those messy paths (and I like the flat, smooth almost molded like appearance I currently get). Lately, I tried using Simplify3D to increase the separation between the nozzle and the PEI for the first layer (setting First Layer Height to 115%) but that didn't seem to work (though I am going to try increasing it to 150% to see if that helps).

Any ideas? Help?

airscapes
Posts: 403
Joined: Wed Jan 31, 2018 11:36 pm

Re: PETG bonds to PEI like superglue!

Post by airscapes » Tue Jan 21, 2020 1:06 am

I have no issue with petg warping on the makergear tape surface (I use the 2" tape )
You did not say if you properly set your starting Z offset, did you set it after you added the PEI to the plate? When printing PETG are you using a fan, as some people on the internet say to do, because you should not. PETG will stick like glue to just about anything if the starting height is correct, i have had it remove a chunk of glass when using it on just glass with nothing else. I have a full size cake icing spatula that I use to smack the part on the first layer which will lift the edge and let me slide the blade under the part.
So my suggestion is to set your starting height using M206 so when a part is printed with the layer height you are planning on using it comes out exactly the height it should be, with first layer set to 100%
If this does not make any sense, please let me know and I will try and explain the details on how to do this.

Hugs
Posts: 88
Joined: Tue Mar 08, 2016 11:16 pm
Location: Pennsylvania

Re: PETG bonds to PEI like superglue!

Post by Hugs » Thu Jan 23, 2020 3:36 am

shinigami wrote:
Mon Jan 20, 2020 9:41 pm
I've seen suggestions online of using Windex or Elmer's glue to weaken the bonding between PEI and PETG but I am reluctant to go down those messy paths
I have one of Insta's MIC6 plates with PEI and when printing with eSun's PETg, I use a thin coat of the purple Elmer's "Washable School Glue" stick. I'm not sure where you heard it's "messy" but it certainly isn't bad for me. Worst case is I have to rinse the finished part under warm water but in 10 seconds, it's perfectly clean.

Also, I concur with Airscape's recommendation to check your starting height (tweaked with "Z offset" in PrusaSlicer and Slic3r) and perhaps raising it a bit so you're not squishing the first layer too much.

airscapes
Posts: 403
Joined: Wed Jan 31, 2018 11:36 pm

Re: PETG bonds to PEI like superglue!

Post by airscapes » Thu Jan 23, 2020 6:00 pm

shinigami, if you will tell us what nozzle size and layer height you are using I can post a couple of calibration models that will let you properly set z offset and extrusion multiplier.

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zemlin
Posts: 461
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Location: Indianapolis, Indiana

Re: PETG bonds to PEI like superglue!

Post by zemlin » Fri Jan 31, 2020 4:28 pm

I have printed LOTS of PETG, almost exclusively on PEI sheet.
To remove parts, I use a 1/2" wood chisel. I lay the back side of the blade flat against the build plate and put the cutting edge of the chisel right at the contact point between the sheet and the part. A light tap with a plastic hammer is usually all that's required to pop the part off - build plate cold. I have recently moved to the powder-coated PEI spring steel plate on a magnetic base. With that, the plate peels easily off the part with no tools.

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