random under extrusion

Hello,

Please see the picture below.

I believe to have calibrated my printer since when I print the 20mm cube I am within 0.15mm of the target. However for larger prints, I have been noticing this issue under extrusion in 1 area leading to a slight over extrusion just following it. I think I have the steps/mm as a correct approx value for my printer. I am printing abs on kapton tape + abs juice. Could anyone help me out ?

Thanks,

Edited 1 time(s). Last edit at 07/27/2016 06:05PM by blahhh10.

It looks like your bed is not level, or your auto level bed correction is not working. The under extrusion is probably when your nozzle is in direct contact with the glass, and the over extrusion blobs are probably when the pressure build up wins and pops out for relief.
Edit

Quote
PDBeal
It looks like your bed is not level, or your auto level bed correction is not working. The under extrusion is probably when your nozzle is in direct contact with the glass, and the over extrusion blobs are probably when the pressure build up wins and pops out for relief.
Edit

I am using auto levelling and I do think it is working since I am printing small objects just fine and am getting an auto level correction matrix and running a g29 autolevel grid before every print.

EDIT : just realized my grid might be too small and hence it isn't checking the whole bed and what you're saying may very well be the issue. Do you think it might be grid size ?

As far as I understand, you get better results with the largest test grid you can do which I've always translated to the for extreme corners of my bed.

Quote
PDBeal
As far as I understand, you get better results with the largest test grid you can do which I've always translated to the for extreme corners of my bed.

I think it's working now. Thank you so much!