Also known as “hairy prints,” stringing is one of the most annoying – and common – 3D printing problems.
It can occur with any kind of filament and on any printer, even though the Ender 3 seems more affected by this issue.
Generally, 3D print stringing is the result of incorrectly set parameters. Not enough retraction or an excessive nozzle temperature can lead to stringing. Wet filament is another common culprit, especially for highly hygroscopic materials like PETG. Nozzle contamination, a defective nozzle, and poor filament quality are other possible causes.
What Is Stringing Or Oozing?
Stringing is a phenomenon that happens when thin filament strings are left behind on a 3D printed model.
This phenomenon is also called oozing or hairy prints, a name given by the hairy aspect of plastic strings. However, the strings’ appearance can vary from thin to thick spikes and even blobs of material.
Aside from aesthetic considerations, stringing can affect the strength of your prints and it could lead to layer separation. That’s because most factors that cause stringing also affect material adhesion and the overall print quality.
To ensure a high print quality, you should make sure no oozing happens during the printing process.
A 3D print stringing test is the quickest and most accurate way of telling whether your material is prone to stringing (or whether you have to tweak up your printer’s settings).
The test basically consists of printing calibration structures (towers) that can tell you which setting you have to adjust. Running such a test is crucial especially if you suspect that the culprit is your machine – Ender 3 stringing, for instance, is particularly common even if the filament is dry and of good quality.
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To run a stringing test in Cura:
- Open your slicer and go to Extensions.
- Select Part for calibration, then Add [the material you’re printing with] TempTower. E.g., Add PLA TempTower. You may have to add the Calibration Shapes plugin to Cura if you don’t have it already.
- Select the printing temperature and retraction settings you’d normally use for the chosen material.
- Print the tower.
- If stringing occurs, modify the parameters in small increments until oozing is no longer a problem.
If stringing still occurs regardless of the parameters, the most likely problem is the filament’s quality, moisture content, or a damaged nozzle.
What Causes Stringing In 3D Printing?
Stringing in 3D printing can be more than an aesthetic nuisance, and fixing it is crucial. Here are the most common causes and what to do about them.
1. Wet Filament
Printing with wet filament is one of the most common causes of 3D print stringing on the first layer – and all subsequent ones.
This happens because the moisture inside the filament is heated by the heat block past its boiling point. Water turns into vapor that mixes with the melted plastic and increases the probability of oozing during non-print movements.
Stringing aside, printing with wet filament also leads to other visual and structural imperfections.
How To Fix
Storing filament properly and drying it before use can help you fix the issue.
Highly hygroscopic materials, such as PETG, should be stored in airtight boxes together with a bag or two of desiccant. Keep the box in a dry and cool room, away from sunlight.
You can dry filament in a number of ways, depending on the equipment you have.
A filament dryer should be your top option. However, if you’re a beginner and don’t want to buy a filament dryer just yet, you can also dry the spool in the kitchen oven or a food dehydrator.
Some filaments, such as PETG, can also be dried in the freezer or in a vacuum chamber.
Alternatively, you could dry the filament on the printer’s heated bed – even though this should be your last resort.
2. Poor Filament Quality
All FDM printing filaments are made of some kind of plastic, a material that is susceptible to heat.
High-quality filaments have more stable formulas and melt when reaching the melting point specific to the material. However, poor quality filaments can be blended with less stable compounds that have a lower melting point.
Yet, you still have to heat the filament to the melting point of the plastic you’re using, such as PLA or ABS or PETG.
This leads to oozing, since part of the filament will melt faster.
Moreover, low-quality filaments are more hygroscopic than high-quality ones and are more difficult to dry properly.
How To Fix
There is little to do if stringing happens due to the material’s poor quality. The only way to fix this is by investing in high-quality materials.
Buying high-quality filament is crucial, especially if you’re a beginner. Otherwise, you may find 3D printing extremely challenging.
3. Filament Type
Regardless of the filament quality, some materials are more prone to stringing than others.
For instance, PLA, ABS, and PETG are all notorious for stringing. Yet, PETG is the hardest to work when compared to both PLA and ABS.
How To Fix
Staying away from oozy filaments can be a solution, but perhaps not the best one.
A better idea is to learn the printing parameters each material requires and make sure the printer is set correctly each time before hitting the start button.
While general guidelines exist for each material, you should read your specific product’s label. As explained, the actual formulas of each material may slightly vary from one brand to another, which means that parameters may vary, too.
You should also make sure to store the filament as instructed by the manufacturer.
4. Incorrect Retraction Settings
Enabling retraction is one of the most common pieces of advice you’ll get when asking how to solve stringing issues.
That’s because this setting moves the heat zone higher up from the tip of the nozzle. Hence, the material is less likely to ooze during non-extrusion movements.
How To Fix
If stringing mostly happens during non-extrusion movements, enabling retraction might fix the issue.
Retraction settings tend to vary from material to material and brand to brand.
For PLA, for instance, the optimal retraction settings that work for most brands are:
- Retraction distance: 2mm
- Retraction speed: 40mm/sec
- Retraction minimum travel distance: 0.6mm
However, you may have to alter these parameters for certain PLA brands. The same is true for other materials, such as ABS and PETG.
5. Excessive Nozzle Temperature
Once you’ve figured out retraction settings, the next most common culprit for stringing is the nozzle temperature.
The reason behind it is pretty simple – the higher the temperature, the more fluid the material will become. Any type of plastic filament becomes stringy if heated way above its melting point.
How To Fix
Like retraction issues, stringing due to excessive nozzle temperature is easy to fix.
To find the extrusion sweet spot, set the temperature at the highest limit recommended by the manufacturer and decrease by 5°C at a time until oozing stops.
If you’ve reached the lower limit and stringing is still an issue, you may have to fix other parameters or change filament quality.
6. Incorrect Feeding Rate
Another factor that can lead to stringing is an incorrect feeding rate – oozing can happen due to over- and under-extrusion alike.
In case of over-extrusion, the excess filament forms oozing blobs and leads to a distorted geometry of the print. Excess material may also ooze from the nozzle during idle movements, further contributing to the stringing process.
Under-extrusion is responsible for gaps between layers, but the printer still feeds the filament continuously. Hence, the gaps transform into hairy strings.
How To Fix
Setting an optimal feed rate for the type of filament you’re printing can solve the problem.
The optimal feed rate can also be determined by the type of machine you have. For instance, a feed rate of 40 to 50mm/s is ideal for detailed printing with an Ender 3.
For the same printer (V2 or Pro models), a feed rate between 70 and 80mm/s is ideal for prototyping and rougher prints.
7. Low Print Speed
The print speed is another factor affecting 3D printer stringing.
Oozing generally happens during idle, non-extrusion movements and is correlated to a lack of retraction or improper nozzle temperature.
If the arm moves too slowly, the filament can leak and lead to stringing. The problem is more common for certain filament types, such as PETG.
How To Fix
Adjust the travel speed to at least 150mm/s and up to 200mm/s, depending on the printer and material you work with.
Adjusting the Z hop could also help fix the issue.
8. Nozzle Problems
A dirty nozzle, one that is too large for the job, or a defective nozzle could also lead to stringing.
How To Fix
As a rule of thumb, you should clean the nozzle after each print. Use a brass brush or an alcohol wipe to remove excess material from the tip.
Ender 3 printers (as well as other printer brands) come with a cleaning needle that you can use to dislodge and remove larger clogs.
For most material, a 0.4mm nozzle works just fine, but you may want to switch to a smaller diameter if the filament is particularly oozy.
Also keep in mind that nozzles wear out and must be replaced in time. Check the nozzle tip and if it’s dull, it is time to invest in a new nozzle.
3D Print Filaments That Are Prone To Stringing
As mentioned, some filaments are more prone to stringing than others. Among the most common choices, ABS, PETG, and PLA are the most challenging to work with.
ABS is a very sturdy and flexible filament known for its increased lifespan and higher melting point. The material can benefit from over-extrusion, and stringing mostly happens due to too fast cooling or incorrect retraction.
For the best results, you should set the nozzle temperature to 230°C and set a retraction distance of 5mm at a rate of 45mm/s. Also, heat the bed to 110°C if you’re using an Ender 3 and enhance adhesion, especially on PEI surfaces.
PETG is one of the most difficult materials. It is highly hygroscopic and can absorb moisture from air in minutes. Hence, it can easily become wet after thorough drying.
The material also oozes easily. Thus, you should set a faster travel distance for the idle movements and consider using a printer enclosure to minimize air exposure.
A retraction distance of 6mm is also recommended for Ender 3 users.
Similar to PETG, PLA tends to absorb moisture from air quickly. Printing in an enclosure is recommended for this material, too.
Retraction settings on your Ender 3 should start at 5 mm distance. Increase or decrease by 1 mm until all stringing is gone.
To avoid PLA stringing, you should also set the retraction speed to 50mm/s.
Stringing is a common problem regardless of the 3D printer or filament type you’re using. Yet, Ender 3 users and those printing with PLA, ABS, or PETG are more likely to run into this issue.
Setting the right parameter – especially the right retraction speed and distance – can help solve the issue. You should also avoid printing with wet filament. Moreover, remember to keep the nozzle clean.