PLA Lifting in Back

Hi everyone,
So I've been having an issue I cant seem to track down no matter what I try. In the back of my prints specifically while the brim is being laid down the print starts to bubble up and not stick to the bed at all. This only happens in the back of my prints though which I find odd. Another thing I find odd is that I can print abs absolutely no problem and the part sticks to the bed so well you could probably pick the printer up before the part came off. I have set my first layer height time and time again and leveled my bed as precisely as possible over and over with no avail. I've tried increasing and decreasing bed and nozzle temperatures. But still what I find odd is that no matter what I do this only happens in the back.

Google Drive Video + Photo Link

In this link there is a video of this happening. This was after I set the nozzle height and leveled the bed again. I also cleaned the bed prior with IPA. Bed was 60c and extrusion temp was 200c. If you watch the video you'll see whats going on it almost appears as over extrusion. Another odd thing that I find is if you go to the hand photos folder there are pictures of this exact piece form the video, if you look at the left and right they seem very steady and the back looks bad as of my issue but, if you pay attention to the front photo it doesnt look quite right as well. So quite possibly this is an issue with the axis?

See if this helps...

[forums.reprap.org]

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Waitaki 3D Printer

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Edited 1 time(s). Last edit at 04/26/2017 03:10AM by waitaki.

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Waitaki 3D Printer

Assuming the glass is clean, with alcohol or something.....

Then there are 2 likely reasons for this
1) since it only happens in back, the bed is too close to the nozzle
2) you are overextruding

To check #1, pull up the first layer look at the bottom the 3 sides that work will likely look smooth and not broken the back will look broken, lines going across the extrusion line, meaning it is too close to the glass

The first layer is the most critical, the height has to be exact, lower the back just a bit and you may find the issue resolved

I completely agree with the the bed being too close to the nozzle. I believe my glass is warped. I will report back when I get new glass to confirm this if this is the case for other users. As for the post from waitaki, I did try reducing my first layer height and this "worked" in some cases. I believe this was a band aid to another problem, which I think is warped glass.

You should look at moving to a 3 point levelling system. 3 points define a plane and its easier to get a level bed. 4 points over constrains the bed and leads to warping / bowing. If you do a search of the "digital_dentist and 3 point levelling" you should get some good info, he is a user on this forum and gives good advice and improvements.