Cracks appearing in a new 800um PEI Sheet

Hi
I have recently purchased a 800um PEI sheet from Orballoprinting.com. Just after the sheet was installed and heated for only a few prints I noticed the cracks shown in the attached pic. My bed temp is 85 deg C. as verified with a separate digital thermometer. My PEI sheet is fixed with 3M 468MP 200MP adhesive to a 6mm aluminium plate.The crack extends for about 60 mm in length and has a fork lightening shape. Anyone know what might be causing this or have had similar experiences? The only similar problem I found on the web is documented at [forum.makergear.com]

Edited 2 time(s). Last edit at 02/07/2018 04:10AM by parto.

I have a 2mm thick PEI sheet on my printer, after a few dozen prints it developed cracks and now after a few hundred prints they are everywhere, no effect on printing tho....

Thanks JustSumGuy. Appreciate your input. Can you post a picture? Do the cracks penetrate right through the full thickness of the sheet? On my pei sheet I can feel the crack edges on the sheet surface by running my finger over the crack. In other words the crack comes right to the surface. I'm afraid to print in this area of the bed in case removing the part tears the pei sheet.

Following with interest. I have a round PEI sheet in the mail, so I can compare it with Buildtak, LokBuild and blue tape.
The link you posted has an error in it. it only leads me to http/:url. But with copy/paste I was able to open the site. Not much helpful information there yet.

I believe, the cracks could be avoided by preheating bed and sheet to a medium temp ( say 70°C ) before pulling off the cover sheet of the sticker.
Or is it a production issue?

I have no pics and may not be able to get any for a few days, I can say I dont feel the cracks tho....

feels smooth, I sanded the surface a while back due to some scratches from hasty removal

the cracks look like when treated glass gets broken.....

Likley what oLamp said tho, I did not heat the bed b4 install....

I have PEI on two printers. It's yellow. I don't know what that plastic you have is, but I don't think it's PEI. I have never seen any cracks in the PEI on my printers.




Edited 1 time(s). Last edit at 02/14/2018 08:01AM by the_digital_dentist.

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

My current printer has alot of learning on it if you get me....
2mm PEI sheet that was put on cold... I think that is the reason its all cracked up

My new HEVO build will have a .8mm sheet of PEI put on hot.....

attached is a pic...

but like I said, it does not affect the print... The cracks are just visual.... for effect

Here's a better pic of the crack with a metric ruler in view to give a scale perspective.