Square-Tube-Connector

This Project Square Tube Connector I made this connectors because i need them for project all our base on "Square Tube" from 20x20mm I will add more as I will make them

because with setting i have before sometime parts break i alter my setting
I will try Put All settings in here

My PLA :
RepRap Filament Black 1.75 1000g (barcode 8719345005572)
Buy At RepRapWorld.
Very good Filament

Using Cura 3.0.4
I use standard Profile :
*PLA Draft Quality 0,15

And change to :

Wall Thi