Stringing is one of the most common and frustrating issues encountered in 3D printing. If you’ve noticed thin strands of plastic appearing between different parts of your model or across gaps, you’re dealing with stringing. While it doesn’t necessarily affect the functionality of your print, it can significantly impact the quality and appearance of your models.
Fortunately, stringing is a problem that can be resolved with the right techniques. In this article, we’ll explore the causes of stringing, its impact on your prints, and the best methods to prevent it from occurring.
What Is Stringing in 3D Printing?
Stringing occurs when the nozzle oozes out filament while moving between different sections of the model, leaving behind unwanted threads or “strings” of material. This happens primarily during travel moves, where the printhead moves from one area to another without extruding material. The molten filament continues to drip out of the nozzle, causing fine strands to form across open spaces.
Common Symptoms of Stringing:
- Thin, hair-like strings between different parts of your print.
- Excess filament left behind in areas where no extrusion is intended.
- Unwanted filaments hanging off the print.
Although stringing doesn’t always affect the structural integrity of the print, it can ruin the aesthetic quality, especially for highly detailed or visually sensitive models.
Causes of Stringing in 3D Printing
Before you can effectively prevent stringing, it’s essential to understand what causes it. Several factors contribute to stringing, and addressing each of them will help you achieve cleaner prints.
1. Excessive Retraction Settings
Retraction is a setting in 3D printing that pulls the filament back into the extruder when the print head moves over an empty space. If the retraction settings are too low or incorrectly configured, the filament doesn’t get pulled back far enough, allowing it to ooze and form strings during travel.
Symptoms of Incorrect Retraction Settings:
- Visible strings across gaps or between print sections.
- Inconsistent extrusion during travel moves.
2. High Printing Temperature
Printing at too high a temperature can make the filament overly runny or gooey, which increases the likelihood of stringing. High temperatures allow the filament to remain molten and drip out of the nozzle even when it’s not supposed to.
Symptoms of High Temperature Issues:
- Excessive stringing between parts.
- Oozing of filament while the print head moves.
3. Too Much Extruder Speed
If the extruder is feeding filament too quickly, the nozzle may not be able to keep up with the rate of extrusion. This can cause over-extrusion, leading to excess filament that strings out across the model during travel.
Symptoms of High Extruder Speed Issues:
- Filament buildup and blobs on the print.
- Stringing and poor-quality layers.
4. Low Travel Speed
The speed at which the print head moves between different parts of the print is another important factor. If the travel speed is too slow, the nozzle has more time to drip filament, leading to more stringing. Higher travel speeds help reduce the chances of filament oozing.
Symptoms of Slow Travel Speed:
- Increased stringing between parts.
- The nozzle appears to “drip” material while moving across gaps.
5. Incorrect Nozzle Size
If your nozzle size is too large for the type of print you’re doing, it may extrude too much filament, leading to stringing between parts. Smaller nozzles tend to reduce the chances of stringing because they extrude material more precisely.
Symptoms of Incorrect Nozzle Size:
- Excessive filament being extruded.
- Inconsistent extrusion causing visible strands.
How to Prevent Stringing in 3D Printing
Now that you know the common causes of stringing, let’s dive into practical ways to prevent it. From fine-tuning your printer’s settings to selecting the right materials, there are several steps you can take to eliminate stringing and improve the quality of your prints.
1. Adjust Retraction Settings
Proper retraction is key to preventing stringing. Retraction settings dictate how far the filament is pulled back into the extruder when the nozzle is moving between parts. Increasing the retraction distance and retraction speed will help prevent the filament from oozing during travel moves.
Steps to Adjust Retraction:
- Retraction Distance: Increase the retraction distance slightly. A typical starting value is around 1 mm, but you can increase it up to 6 mm, depending on your printer and filament type.
- Retraction Speed: Increase the retraction speed to around 30–50 mm/s. This helps to pull the filament back faster, preventing it from dripping out while the print head is moving.
- Retraction Minimum Travel: This setting determines the minimum distance the print head must travel before retraction is activated. A value of around 1 mm usually works well.
2. Lower the Printing Temperature
A high printing temperature can lead to excessive filament oozing, which increases stringing. Lowering the print temperature can help reduce this problem.
Steps to Adjust Temperature:
- PLA Filament: Lower the temperature to between 190°C and 210°C.
- ABS Filament: Adjust the temperature to around 220°C to 240°C.
- PETG Filament: Keep the temperature between 230°C and 250°C.
A good practice is to lower the temperature in increments of 5°C to see where stringing is minimized without affecting adhesion or print quality.
3. Increase Travel Speed
Increasing the travel speed (the speed at which the print head moves between different areas of the print) can help reduce stringing. A faster travel speed reduces the amount of time the nozzle spends over empty space, thus decreasing the chances of filament oozing.
Steps to Adjust Travel Speed:
- Increase the travel speed to at least 100 mm/s or higher, depending on your printer’s capabilities.
- If your printer supports it, use “Jerk” or “Acceleration” settings to further optimize the speed of the movement.
4. Reduce Extruder Speed
Slowing down the extruder can help reduce over-extrusion and excess filament buildup, which can lead to stringing.
Steps to Adjust Extruder Speed:
- Lower the extruder speed to avoid overfeeding the filament. A common setting for extruder speed is between 25 mm/s and 40 mm/s, depending on your filament and the print’s complexity.
- If you see under-extrusion or poor adhesion, slightly increase the extruder speed.
5. Enable “Combing” in Slicing Software
Many slicing programs offer a setting called “combing,” which helps to prevent stringing by keeping the nozzle inside the printed areas during travel moves. By enabling this feature, the printer will avoid moving over empty spaces and will instead travel within already printed areas, reducing the chance of stringing.
Steps to Enable Combing:
- In your slicer (such as Cura or PrusaSlicer), enable “Combing Mode” or “Combing in Infill”. This setting keeps the nozzle from traveling over open spaces and will only move within the existing print areas.
- Combine this with higher travel speeds for the best results.
6. Use Filament with Less Stringing Tendency
Not all filaments are equal when it comes to stringing. Some filaments are more prone to oozing and stringing than others. By switching to a filament that is less prone to stringing, you can achieve better results without having to fine-tune your printer too much.
Filament Recommendations:
- PLA: This is the most forgiving filament for stringing and usually requires minimal adjustments to prevent it.
- PETG: PETG is prone to stringing but can be controlled with proper retraction and temperature settings.
- ABS: ABS can string but tends to print with better consistency when you adjust your settings properly.
- TPU: Flexible filaments like TPU are prone to stringing but can be managed with slower print speeds and lower temperatures.
7. Use a Z-Hop Feature
Z-hop is a feature that lifts the nozzle slightly when traveling over gaps, preventing it from dragging filament across the model. This is particularly useful when printing intricate details or parts with small gaps.
Steps to Enable Z-Hop:
- Enable Z-hop in your slicer settings. A typical Z-hop height of 0.2–0.4 mm is effective at reducing stringing without compromising the print quality.
- This feature helps to ensure that the nozzle doesn’t scrape over printed areas, reducing the chance of stringing.
8. Clean the Nozzle Regularly
A clogged or partially blocked nozzle can exacerbate stringing problems. Regularly cleaning the nozzle can help ensure consistent extrusion, which reduces the chances of stringing.
Steps to Clean the Nozzle:
- Heat the nozzle to the printing temperature and perform a cold pull to remove any debris.
- Alternatively, use a needle or nozzle cleaning kit to clear out any residual material.
- Keep the filament path free of obstructions and clean the extruder gear periodically.
Conclusion
Stringing is a common 3D printing issue, but with the right adjustments to your settings and print environment, it’s entirely preventable. By fine-tuning your retraction settings, adjusting temperature and speed, and choosing the right filament, you can significantly reduce stringing and achieve smoother, cleaner prints.
Regular maintenance of your printer and understanding the specific needs of your material will also go a long way in preventing stringing. Armed with this knowledge, you’ll be able to enhance the quality of your prints and create professional-level models with ease.