Hello all and let me say thanks from the start for any help!

I just started out in 3d printing, and the printer that I have is a Printrbot Simple 2014.

I am sure that I have it calibrated to the best I can 20mm squares are printing at 20.01mm.

Here are some images of what is happening:

photo 1.jpg
photo 4.jpg
photo 2.jpg
photo 3.jpg

If it is my calibration then I can redo that, but I am wondering if it might be voltage, heat or mechanical.

Thanks again for any help.

Mark

Edit:
Forgot to mention that I have a Printrbot Simple 2014 Kit.