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PETG stringing: How to fix stringing in your 3D prints

PETG stringing: How to fix stringing in your 3D prints

Stringing is a common problem in 3D printing that occurs when melted filament oozes from the nozzle while the nozzle is traveling between two points, leaving behind thin strings of filament that resemble hairs. Stringing can be a major annoyance, as it can mar the surface of a print, and can be difficult to remove. This problem is particularly pronounced when printing with PETG filament. 

Example of Stringing in PETG

Example of Stringing

PETG filament is a popular material for 3D printing because it is strong, durable, and has a low tendency to warp. However, it requires a relatively high temperature to melt, which can make it more prone to stringing. Additionally, PETG has a tendency to stick to the nozzle, which can cause filament to ooze out even when the nozzle is not in use. 

Fortunately, there are several tips and tricks that can be employed to prevent stringing when printing with PETG filament. In this article, we will explore five of the most effective strategies. 

Before doing any of these, first make sure your printer's hot end is clean and free from any debris. PETG filament is known to leave residue inside the nozzle, which can lead to clogs and stringing. Clean the hot end regularly and perform routine maintenance to ensure the printer is in good working order. 

1. Adjusting Retraction Settings 

The first step in preventing stringing is to adjust the retraction settings in your slicer. Retraction is the process by which the extruder motor pulls a set distance of filament from the nozzle, preventing unwanted oozing. By adjusting your retraction settings, you can fine-tune the amount of filament that is retracted, and the speed at which it is retracted. 

In general, it is recommended to start with a retraction speed of around 25 mm/s, for both Bowden and direct drive extruders. For Bowden extruders, a retraction distance of 6 or 7 mm is recommended, while for direct drive extruders, a retraction distance of 3 or 4 mm is preferred. These settings can be adjusted in small increments to achieve the perfect retraction settings for your printer. 

If stringing persists, try increasing the retraction speed by 5-mm/s increments. Be careful not to set the speed too high, as this can cause the nozzle to jam. You can also try increasing the retraction distance by 1-mm increments. 

Another related setting to consider adjusting is the minimum travel distance. This setting determines the minimum distance that the printhead must travel before fully retracting the filament. By reducing this distance, you can ensure that even small distances are free of strings. 

2. Decreasing Nozzle Temperature 

If adjusting retraction settings doesn't solve the problem of stringing, the next step is to decrease the temperature of the nozzle. When the filament gets too hot, it can freely ooze out of the nozzle, regardless of the retraction or travel settings. By decreasing the nozzle temperature, you can reduce the likelihood of stringing. 

To determine the ideal temperature for your printer, try printing a temperature calibration block or a "temperature tower". These tools come with instructions to help you find the perfect nozzle temperature in a single test. Be careful when adjusting the temperature, however, as you do not want to eliminate stringing at the cost of a smooth surface finish. 

Temperature Tower to reduce PETG stringing

Temperature Tower (Image krpavlu via Thingiverse)

3. Increasing Travel Speed 

A potentially quick fix for PETG stringing is to increase travel speed. The quicker the nozzle moves between two points, the less time melting filament will have to ooze. As the article mentioned, try increasing your printer's travel speed in 10-mm/s increments until you find the perfect speed.  However, keep in mind that increasing travel speed too much can lead to other issues like layer shifting or reduced print quality. So, it's essential to find a balance between travel speed and other print settings. 

4. Decrease Layer Height 

Try printing with a smaller layer height. A smaller layer height means the printer will be depositing less material, which reduces the chances of stringing occurring. Keep in mind that this will also increase print time, so adjust accordingly. 

5. Find the Right Brand 

Lastly, you can try using a different brand or type of PETG filament. Not all PETG filaments are created equal, and some brands may be more prone to stringing than others. Experiment with different brands and types of filament until you find one that works well with your printer and doesn't string excessively. Quality filament, such as Protomaker PETG filament can make a big difference. 

In conclusion, stringing is a common problem in 3D printing, particularly when printing with PETG filament. This issue occurs when the melted filament oozes while the nozzle is traveling between two points, resulting in unwanted "hairs" on the print. However, by tweaking retraction settings, reducing minimum travel, decreasing nozzle temperature, increasing travel speed, printing with a smaller layer height, and experimenting with different filaments, you can prevent stringing and produce high-quality prints. Keep in mind that finding the right combination of settings and filaments may take some trial and error, but with patience and perseverance, you can achieve excellent results and avoid PETG stringing in your parts.

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