3D printing: Stringing and how to fix it

Does your 3D print have weird strings like in the picture? Fortunately, they can be removed rather quickly with a lighter, but of course it's optimal not to have them in the first place. There are a few reasons why this occurs.

Lack of retraction

Retraction is a feature specifically for counteracting stringing. The slicer ensures that the filament is withdrawn from the hotend each time the print head travels to another part of the model. As a result, the pressure in the nozzle becomes minimal and therefore has difficulty leaking out while in motion. The length of the retraction usually has a direct relationship with the length of your PTFE tube (the tube your filament travels through from where it's inserted, to where it enters the printer hotend). Normally, 4-6 millimeters of retraction will be needed on a printer with a bowden extruder (extruder that has a tube where the filament travels). On direct drive extruders (where the filament is inserted directly into the printer hotend), the retraction can be significantly shorter due to the short distance between extruder and hotend.

Old filament

Old filament that has been left out in the humid air can draw a surprising amount of moisture from the air. Over time, this can result in stringing no matter how much retraction you set. Filament can be dried in an oven at 40-45 degrees for a couple of hours, or using a food dehydrator machine (many food dehydrators can be modified to dry filament).

Printing too hot

If you have the right length of retraction and a dry roll of filament then check if the temperature is set correctly with respect to the suggested temperatures for your filament. If the temperature is right, you can turn 4-5 degrees down. This can be the boundary between the filament that stays in the nozzle and the filament that seeps out.

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Published: Oct 2020, updated: Jan 2021