Outer most perimeter not sticking on one side

Hello everyone

So I've got this Printer that I basically just cobbled together from some stuff I had lying around. The head moves in x and y and the bed moves up and down, its kinda like a bq witbox in terms of gantry design.

Now the Problem is that when I print a cube, or anything with a flat side, the outermost perimeter won't stick to the other Perimeters and I can easily peel it off with my fingers. This only happens on one side ( the "-y" side).

I already tried the following things:
Printing it on other spots on the buildplate
Printing with a raft
Printing after auto tramming it with Mattercontrol
Printing with more Perimeters (tried up to 6 Perimeters)
Calibrating the extruder
Using different slicers (matterslice, slic3r and cura)
Printing the Gcode on different printers. (It worked fine)
Increasing the extrusion width

I suspect that my z-axis is somehow not moving straight down, but then again, all other sides are completely fine, and it stops happening when I turn the part about 20° around the z axis. So before I start taking the z axis apart I thought I'd ask first.

Any help would be appreciated

Edited 2 time(s). Last edit at 02/18/2016 11:21AM by Ramon3D.

You tried a lot of things and sound like you spent quite some time doing so...
But did you actually calibrate the entire machine?
I mean not just playing around with the extruder stepping because of being desperate but actuall calibrating all?
This means using digital calipers, adjusting the stepping for the motors, checking if everything is straight (measure, not jus assume!)...
For example: You can try to adjust what you want and for how long as you like, if your one of your axis is not 100% parallel to the others AND the build platform it will never work right...

Yes, I did calibrate the whole machine, anything that doesn't have a flat side facing -y is printed pretty nice and dimensionally accurate.

It just confuses me that it happens everywhere on the buildplate and not just at the end that is as far away from the guide rails as possible, and the problem looks the same in each spot on that one side.

Edit: okay i just found whats wrong... One of the pla parts that holds the rods at -y cracked a little bit... And so the whole thing sags a little bit on that side. That would explain why it used to print nicely and it suddenly just started making problems. Probably happend while i was moving the printer to my basement.

Edited 2 time(s). Last edit at 02/19/2016 02:53AM by Ramon3D.

Well, that certainly is a problem, but one you can fix quite easy.