Persistent Warping with PETG

[airscapes]

with a 4mm nozzle I would be printing the part at a .3mm height and and extrusion width of .4mm
your first layer should be .3 just like every other layer when the staring height is correct.
Your bed should be 70 C
If using eSun petg the nozzle should be 230- 235C
Not knowing your part size speed should be slower than what you would print PLA

When you set up your printer there is probably some point when they tell you to put paper under the nozzle.. that would be manually setting you Z offset or starting height.

Within most slicers is a place where you can insert a Z offset positive and negative. Not sure which move the nozzle away from the bed and which moves it closer you will have to experiment of find documentation on the setting. I use a different method using the firmware M206 command.

What you will do is set your slicer as i suggested above with starting layer just like all the rest of the layers .3mm extrusion width .4mm if that is something that get set within your slicer.

Print the square and it should be 3mm +- .02mm so 2.98 - 3.02 mm tall
If not use that Z offset and make small adjustments until you achieve the proper height
Than print you part.

Also if you designed the part, go back and round the sharp edges, sharp corners increase the warping.