Overextrusion symptoms on solid infill over infill?

I am seeing signs of over extrusion on solid infill that is over a layer of infill. No, the printer is not actually over extruding (extrudes 50mm of filament when it is told to extrude 50mm of filament) but I cannot seem to correct this. Turning down the extrusion rate whilst it is on this layer to 60% will fix the issue, but since the printer is not over extruding there should be another cause. Any ideas?

Just a wild guess, since you're very sparse on details, check the bridging feedrate multiplier, it should be set to 1, maybe yours is at 1.66 or somewhere close. If not you could set it to .6 and see if it's better.

My bridge flow rate was set to 1, so I will try changing it to 60%.

Some more details:

PLA, 200C
No heated bed
speed: 40 mm/s

I think setting the proper extrusion steps per mm is just the first step of the calibration process. Differences in filament, extruder tolerences, and even the hotend can mess with how much plastic is extruded. While I haven't tried it yet, it has been recommended to me to print out a pyramid / cubert grid. Sorry I can't link to anything more specific at the moment.

I agree, it looks more like a bridging problem then an infill problem.
Slic3r loves to use much more filament here than required as it seems to assume there is nothing at all under the bridge.
Unless I do real bridging I turn the bridging settings way down to avoid this.

Does it do this over a solid surface at all? If not your setup / settings probably just aren't good at bridging.

---

Master Tinkerer

Turning down the bridge flow to 70% solved the issue. All solid infill is now as it should be. Thanks