Straw

[Mike1952 0]

I have an Geeetech A20T and when I did my first couple of prints they were great,,, but now for some reason my prints are like straw...like they have no outer walls... I can mash them in my hand like straw 

[dmitche3 0]

I have this happen to me on occasion.  I won't say with 100% certainity but I fix the issue by upping my hotend temps and check my cooling to see if it is apropriate.  As well as  making sure that the lower layers are firmly printing and attaching to the bed.

Also, I make sure to dry my filament.

Combinations of those three fix the issue for me.  I would guess that wet filament is the largest problem followed by the hotend temperature and cooling.