First layer problems with new PEI sheet

[stejan 1]

I have a Creality Ender 5 pro with a Micro Swiss all metal hot end and CR-touch ABL updates. I usually use the standard black creality magnetic flexible print beds which are textured and perform very well when new.

After a while they tend to lose some adhesion so i decided to try a Creality smooth flexible PEI bed has i have heard good things about PEI. 

I have levelled the bed and set the z-offset to what i am pretty sure is optimal but i am getting issues with the first layer.

I am using my normal Eryone PLA which always performs very well for me on the other build plates but not with this new sheet. Has you can see from the first image the first layer is all 'lumpy' for some reason. The second image shows the same print on layer 3 which shows that it isnt a partial clog or filament issue.

It seems to be some sort of problem with the PLA somehow reacting with the PEI bed. I am pretty sure that the offset is has good has i can get it, any lower and it tends to lump even more, and any higher and the adhesion suffers.

Any ideas or thoughts on possible causes?

 

 

[stejan 1]

UPDATE - Here is an image of two finished parts. The top one was printed on the textured black mat and the bottom one on the smooth PEI sheet. These parts are printed face down so the first layer is crucial.

The bottom one is actually super smooth to the touch but those lumps have made it look very untidy to look at.

 

 

[stejan 1]

Anyone ?