I run quite a few Ender 3 Pro's using the same slicer settings (Simplify3D), and just recently I have noticed a very odd extrusion problem.
I find that at about the same height on several printers the printer under extrudes by quite a margin. After that, it either continues to under extrude for the rest of the print or it will go back to extruding proper amounts of filament with no problem. This destroys the print and makes it both structurally weak and defective. I am wasting quite a bit of PLA trying to fix this problem so any help would be appreciated.
Here is what I have done so far:
I first made sure that the hobbed gear is clean.
I tried extruding the filament with a very hot temp (240C) there were no problems here and the filament extruded fine albeit, it was not on the bed, just extruding into the air to see if the problem was heat.
I tried the same thing as above but with a low temp (180) this also proved just fine again extruding in the air.
I calibrated my E steps per mm, those are fine and accurate.
I tried increasing my flow rate to 118%
I tried switching to a different nozzle
I tried switching to a different hobbed gear
I tried switching the mechanism that pushes the filament up against the hobbed gear
That's about it. Not sure where to go from here so if anyone out there can think of anything I missed, I would love to hear it!
As per @fred_dot_u asked, the elapsed time at the layer of failure is roughly four hours in. I have also attached a picture of one example of this kind of failure below. I would also like to mention that this is happening on several of these printers as I have 18 printers running in one room. Our current theory is that the power draw is simply too high and so the printers are not getting the heat they need, however, the thermistors still register a solid 195C on my printers that are currently running.
EDIT 2: Here is another picture of a different model with the same layer failure problem but at a lower layer height. This model was printed along with 11 other identical models on the same bed, all of which failed at the same height.