What could be causing this spotty extrusion?
I'm getting this printing where it's not laying the plastic down very well. What could be causing this? I've printed with these settings before, and it turned out just fine. If you need any other info to properly diagnose this, let me know.
I'm using a Robo3D R1+
This is too fast extrusion vs temperature, slow down the infill speed or increase 15° more the temperature.
Double-check the layer height. @FernandoBaltazar 's comment is probably the answer, but if the amount of extruded material is too little for the Z-height, the material won't adhere to the previous layer.
I´ve seen this in my Prusa due two parameters that may vary your results depending on climate if your printer has not a temperature chamber or having a mechanical issue too.
Lack of extrusion is due a cold filament which it can't reach the melting temperature due a fast extrusion feed; I mean in normal conditions we can print @70 mm/s with 195 °C but on wet or colder days is not possible so I need to slow down the speed (feed rate) with 10 % less than normal to get @60 mm/s or less until get a good flow with out modifying the G-code. If I try to print faster on normal conditions I will get the same lack of material due 195 °C is a low temperature (this is an example).
If I set the temperature 200 °C or 210 °C I will get a better flow and also print faster than @80 mm/s (not affected too much on climate on 100 % feed rate).
For first layer I´m using an speed of 40 mm/s to allow a good adhesion and Z height 90 % of layer height (0.22 typically or 0.18).
Mechanical side: The extruder is not feeding all the filament due a missing pression on the traction gear (filament slip).