Unresolved FIRST LAYER -> Thin perimeters, thick infill

Ok, so for the most part I'm getting great prints,. but there's just one issue that no matter how much I try to tweak the Slic3r settings, I can't get it to work. I'm trying the first layer calibration, where I get it to print a large 1 layer square completely filled in. My problem is mostly with the first layer; the infill vs the perimeters. As you can see in the pictures, my 3 perimeters are not touching well enough to bond, whereas the infill lines are a little too friendly with one another. The infill seems to start out fine, but as more and more lines are draw, each one overlaps the previous one ever so slightly until eventually there's a lot of overlapping going on. It doesn't matter that much for smaller prints, but for prints with a large footprint, it's quite noticeable. So here's the dilemma... under the Advanced settings in Slic3r, changing the Extrusion width of the First layer will affect both the perimeters and infill, and in turn (correct me if I'm wrong on this) will override all other settings for Extrusion width. Now I'm not sure if I fully understand Extrusion width. My understanding is that it makes the lines wider, but does it do this by extruding extra plastic? Or does it do this by slowing down the printing ever so slightly to allow for more extruded plastic in a given area?

Obviously adjusting the Flow will adjust it for all extrusions, so that won't work. Here's what I've tried:
- Playing with z offset (in increments 20 microns) to bring the nozzle closer to the bed and squish the extrusions, and although that makes the perimeters look perfect, it makes the infill really overlap.
- Raise nozzle by adjusting z offset, but this fixes the infill and makes the perimeters very thin
- My first layer height is 0.2.
- Adjusting speed makes no difference.
- I've measured the filament diameter (properly) and it is perfectly round at 1.75mm with extremely tight tolerances (Hatchbox).
- I've calibrated my E steps and it is bang on.
- I use mesh bed leveling and have my bed very level.
- Extruding temp: 215/30. Anything lower than 215, and the first layer starts randomly lifting as soon as it touches the bed (with this particular filament anyways).
- I don't think it matters, but filament is constantly in a container with 10-15% humidity.
- Using Robo 3D R1+ with Slic3r.

 

Thanks for taking the time to respond, Mark.

But wouldn't lowering the nozzle even more squish the infill more and amplify the problem? It'll fix the perimeters, but smother my infill.
But you know what, I'm going to try another slicer and see if that fixes the problem. I'm also going to try to print on an entirely different part of the bed, just in case I'm printing on an area where the bed is slightly raised.
Hey, while I've got you here, regarding the mesh bed leveling adjustments, do you know how to adjust the increments in the firmware so that when I turn the dial on the LCD, the nozzle goes down 25 microns instead of 50?
Thanks.

 

Unfortunately there are two problems with this:
1. All extrusion width settings apply to layers 2 and above, except for First layer extrusion width.
2. I may be wrong but from my experimenting, I have found that extrusion width is different from infill overlap. I don't believe Slic3r has a feature that adjusts the infill overlap. I think extrusion width simply lays down wider lines, and before moving on to the adjacent line, it takes into account the previous line's width, and moves a little further [on the perpendicular axis] before laying down the next line, thereby maintaining the exact same infill overlap, irrespective of extrusion width.

That being said, does Simplify 3D have the ability to set infill overlap? Or is that not the slicer you use?

 

The "middle" lines typically look like that because of a partial clog in the nozzle or extruder. Try heating up the extruder and extrude some filament and analyze the results. If the filament curls around the nozzle you have a partial clog. If it extrudes straight down, then that is more than likely not the problem. Replace your nozzle and I bet the "middle" layers look better. Always a good idea to check your extruder calibration as well.

I also second that your Z-Offset is a little too high.

 

Thanks Ryan, that's an great suggestion and I will definitely look into that. I didn't think that it could be a nozzle clog. Upon exiting the nozzle, my filament does curl like no tomorrow (only when it's in mid-air).
But I have to say this again, if I adjusted the z offset to bring the nozzle closer to the bed, then my infill will be way too thick. It's already overflowing and overlapping quite a bit as can be seen from the picture. And as far as I know, I can't set the infill and perimeter independently on the first layer.
Thanks again.