I can't seem to understand the margins that Cura uses or how to fix them for my machine. Look at this:
I can't seem to tweak the stuff under machine settings to anything that does this better:
Maybe a bit of dup of Cura not allowing full print area to used, but I think my case is a lot worse and can't be explained by skirts.
I had mistakenly left the setting "one at a time" in print sequence. This meaning the printhead needs a lot of room since it will go back and forth in z.
Cura allocates this extra space even if there's only one object.
That looks like you've got the "brim" set to a very wide value. I know you said it's not explained by skirts --which, as Greenonline pointed out, is not the same as a brim--, but you didn't post that setting. At the same time, make sure you don't have a 'raft' set up.
One other possibility is that your source file actually contains a very large first layer. Try looking at the STL file in Meshlab or Meshmixer to see what's actually there.
