Inconsistent Extrusion Troubleshooting Guide

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Inconsistent Extrusion Troubleshooting Guide

Paul W. 10/5/16: I have just started this page, I am gathering more causes and solutions, and it is not yet formatted or grouped. I will make this into a page formatted similar to the one I did previously: [Shifted Layers]

The causes of Inconsistent extrusion are many, and can be due to various mechanical, electrical, hot-end, and extruder issues. The intention of this page is to help narrow down the causes based on tests and observation.

How to determine if you have a problem with Inconsistent Extrusion or Shifted Layers when there are bands showing in a vertical surface.

Individually print two single walled objects: a circle and a square that are at least 30mm across.

  • Do not print an object that is too small or you will have overheating issues.
  • If using PLA, a fan should be blowing on the print.
  • In your slicer: set perimeters to 1, no top layers, no infill.
  • Alternately, use spiral vase mode so there is no abrupt layer changes.
  • If necessary use a layer height on the taller side so you can see the layers more clearly. A layer height of .20 mm or larger is more visible.
  • Put a mark on the side facing out for reference.

Now look very closely at the inside and outside of the printed object, where a band or artifact is, and look closely at where the banding or artifacts starts on a layer. Take a clear photo and enlarge it to see more detail.

If the perimeter is shifted sideways you will see it pushed toward the inside in places and toward the outside in others. See which directions it's shifted and you'll know:

  • If it's only in the X or Y direction, then the problem is connected to that axis.
  • If its wobbling in a regular sine wave pattern the Z axis may be causing it with a bent lead screw or loose guides, or something else is loose there.
  • If the shifting is random then it may be a driver issue or something catching or loose.
  • If the layer height is inconsistent then it could be issues with the Z axis, drivers, or other mechanical issue.

For these issues: see the [Shifted Layers] page for possible causes and solutions.

Otherwise, if perimeters just get wider and narrower and do not move sideways - then it is caused by inconsistent extrusion.

Causes of Inconsistent Extrusion

(This will be a grid, not sorted yet)

  • Extrusion temperature is too low. The best temperature setting for you depends on your thermistor and where it is measuring the temperature, hot end configuration, and filament.
  • Extruder gear clogging with swarf (filament bits).
  • Extruder missing steps due to low driver current - the extruder also may stall or kick back.
  • Extruder missing steps due to thermal shutdown caused by high driver current or poor cooling.
  • Not enough pressure on the compression bearing
  • Too much pressure on the bearing - causing flattened filament. (Make and use a contoured bearing)
  • Inconsistent hot-end temp due to:
    • PID settings, or
    • Heater block is loose when at working temperature, or
    • Thermistor not seated properly in heater block, or
    • Thermistor wiring issue made worse by movement, or thermistor too far away from where it should be measuring, or electrical interference.
    • Under powered heater cartridge, or low power supply voltage to provide enough heat under load.
    • A fan is blowing on the hot end and cooling it. (Move/duct the fan, insulate the hot-end).
  • Intermittent friction in Hot End:
    • The cold-end fan is missing, or not at full speed at all times, or not ducted properly to cool the heat-break correctly.
    • Filament creep up into the cold zone
    • Retraction distance too large
    • All metal Hot-End and sticky filament like PLA
  • Over-driving the extruder:
    • Extrusion rate too high for the max rate achievable at the current print temp for that hot end (extruder will stall, grind, slip, or skip back)
    • Wild swings in nozzle pressure due to print speed/perimeter width/layer height changes between features - causing the extrusion to stall.
  • Excess friction in the filament path, General:
    • Resistance/friction when pulling filament from the roll.
  • Excess friction in the filament path, Bowden:
    • Sharp bends in the bowden tube, especially at some X/Y/Z positions
    • Filament that is very curly
  • Wiring issues to extruder motor
  • Electrical interference - motor wiring not shielded
  • Inconsistent filament shape - a wide spot jams (or partially jams) the hot end
  • Debris in nozzle
  • Bad driver, or driver types that have problems producing proper microsteps.
  • Bad extruder motor
  • Loose grub screw on extruder gear. Grind a flat on the shaft and use nail polish as a removable thread-locking compound.
  • Retraction too large combined with long travel distances. The retracted filament will cool causing a cold/slow restart.
  • Hot-end not properly primed when starting a print.