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My print lines are bumpy and of varying quality

3D Printing Help Centre


In the 123-3D help centre, we answer all your questions about 3D software and printer settings, problems you may experience during or after 3D printing and other 3D-related topics.

My print lines are bumpy and of varying quality

If you notice that your print lines are bumpy or differ in thickness, you may be experiencing 'inconsistent extrusion’. In order to print a clean and perfect straight line, a constant supply of filament is essential. With the slightest deviation in the filament or feed, you will experience print lines of variable quality that are characteristic of inconsistent extrusion.

How can you solve or prevent inconsistent extrusion?

Inconsistent extrusion has many causes and has adverse consequences for the quality of your entire 3D print. Below you will find an overview of the most common causes and solutions.
  • Ensure a smooth filament feed

    Check that the filament spool can move freely and rotate smoothly without the filament becoming entangled. When there is resistance on the spool that prevents the filament from unwinding easily, this leads to inconsistent filament supply. You can easily check this by extruding a certain amount of filament and observing the above process.
  • Prevent a clogged extruder

    A clean nozzle is essential for high-quality print and clean print lines. If your nozzle is clogged, you can suffer from black spots on your filament for a long time. These are charred filament residues that must be removed so that the nozzle can function properly again. Therefore, check whether your nozzle is clogged with the 'cold pull technique' described in our article about clogged nozzles. 
  • Increase the height of your print layer

    If there is nothing wrong with the filament supply or the nozzle, the values ​​of your print layers may be too low. If your print layers have an extremely low value of only 0.01mm, then the opening through which the filament can flow may be too small. Increase the layer height to see if this fixes the problem.
  • Check the 'extrusion width'

    If you have selected an extrusion width that is significantly smaller than your nozzle diameter, this can lead to inconsistent extrusion. Therefore, make sure that your extrusion width covers 100 to 150% of the nozzle diameter. If you try to print an extrusion width of 0.2mm with a nozzle of 0.4mm, it is almost impossible to produce a consistent straight line. Would you still like to print with a smaller diameter? Then replace your nozzle!
  • Provide high-quality filament

    Many extrusion problems can be traced back to the quality of the filament. This is not only about the composition of the filament, but also about the consistency of it’s diameter. In addition, certain filament types attract water from the air, which in the long run deteriorates the quality and drastically shortens the overall life of the filament. Therefore, consider storing your filament in a dry box

Check the extruder for mechanical problems

If you still experience 'inconsistent extrusion' after checking the above solutions, then the problem is most likely mechanical. The filament is fed through 'drive gears'. If these are not adjusted tight enough, the drive gears have insufficient grip, so that too little filament is fed through. If the drive gears are adjusted too tight, pieces can be bitten away from the filament. This is also known as grinding filament. You can easily check the settings of the extruder in the 3D printer software.

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