Stringing, also known as oozing or “hairy” prints, is the result of filament oozing from a nozzle and forming small strings on the 3D printed part. This happens when the extruder moves from one point to another.
In 3D printing, this is one of the common issues that occurs and the reasons that contribute to Stringing could be many.
Stringing & Oozing can be fixed by adjusting the retraction settings or decreasing the nozzle/hotend temperature so that filament being too liquid reduces. It is said that the retraction length of 3 mm and retraction speed of 50mm/s are good in order to reduce stringing.
This stringing / oozing problem significantly reduces the quality of 3D prints and it needs to be fixed to boost the quality.
In this blog, we will learn more about stringing, why it happens and how to fix it.
What Causes Stringing / Oozing in 3D Prints?
While printing some 3D objects, the nozzle will move through some open spaces before reaching the next printing point.
So while moving through open space the nozzle oozes out some melted filament in the form of strings or hairs. These strings will get formed between 2 points of the object and appear like threads.
This is problematic and needs to be addressed. The first step in fixing this is to identify the causes
Below are some of the major causes for Stringing / oozing:
- Retraction settings are not used at all
- Incorrect Retraction speed
- Nozzle Temperature is too high
- Printing with filament that is moisturous
- Printing with jammed / clogged nozzle without proper cleaning
Till now, we have identified the causes of stringing and now we will go through the solutions and ways to fix stringing & oozing in 3D printing.
We hope that you will be able to fix stringing once you go through the below solutions.
How To Fix Stringing & Oozing in 3D Prints?
Wondering how to fix stringing in 3D printing? Well! there are many solutions available similar to the causes that cause it.
Many times, Stringing can be easily fixed with simple settings such as nozzle temperature, extruder speed, empty distance.etc. Stringing can’t be fixed in one attempt, many trial and errors are needed with many settings to fix it.
The methods listed below are some of the simple techniques that are easy to implement without the need of any external tools:
1. Print with Right Nozzle Temperature
Most 3D users have noticed the increase of Stringing / Oozing whenever the Nozzle temperature is very high. When you notice such a high Nozzle Temperature, immediately reduce it and check for the results
When the nozzle temperature is reduced, the filament liquidity reduces and this inturn reduces the extrusion of excess material thereby reducing the Stringing & Oozing chances.
Those filaments that need high nozzle printing temperature are more prone to stringing. This is due to the fact that high temperature affects the viscosity of the filament.
Having said this, PLA demands less printing temperature, but that doesn’t mean that stringing or oozing won’t occur with PLA.
Follow below step by step procedures and see if it reduces the stringing or oozing
- Start reducing the temperature one step at a time and simultaneously check for any improvements.
- Follow the temperature settings given on the filament box and set the printing temperature within the recommended range for a particular filament type.
- Use filaments like PLA as they melt at lower temperatures.
- Reduce the extrusion speed when you reduce the nozzle temperature. This is because the filament will liquify at a slower rate at low temperature.
- Make some test prints of small objects to find out the right printing temperature. This is because the printing temperatures will vary for different filaments.
- Many 3D users set the temperature 10°C hotter than the recommended range during the first layer for good adhesion. After the first layer the temperature is reduced to the recommended range.
2. Increase the Retraction Settings Values
3D printers contain a pullback gear mechanism within the extruder which is called retraction. Refer to the above video for details. Activate / modify the retraction values in a way that pulls back the semi-solid filament and reduces the pressure on liquid filament without getting extruded.
Most of the time, adjusting the retraction settings alone will fix the stringing problem. When retraction settings are increased automatically the pressure on the liquid flament reduces so that the filament will not leak out while the extruder is moving in an open space.
- Retraction settings will be enabled by default in all 3D printers. But if you face stringing or oozing, then you need to check them.
- Ensure that the retraction settings are always in active state to pull back the filament everytime when the nozzle is passing over an open space.
- The best retraction speed to start with is 50 mm/s and vary in 5-10mm/s until stringing stops. Also, keep the retraction distance at 3mm and do the 1mm variations until the good results.
- You can also make use of the Combing Mode feature which makes the extruder to travel only in already printed pathways rather than an open space.
In order to set the right retraction settings, print his Retraction test on Thingiverse which is created by deltapenguin. This is a great object to print and tune-up your retraction settings to the correct values.
The retraction values are not universal, it varies for different users and materials. If one user sees a great result with retraction speed of 70mm/s and 7mm retraction distance, while other users may not see the same.
3. Print Speed Adjustment
The print speed is another factor that can significantly increase or decrease stringing especially while printing at lower temperatures.
Speed reduction is important while printing at lower temperatures. This is because the filament melting time increases and takes time to get extruded. So if the print speed is not reduced then it causes the under extrusion as the filament is less runny.
On the other hand, if you print at high speed and high temperature, the effect of Stringing or Oozing is bound to occur in your 3D prints.
- Be mindful to reduce the print speed at lower temperatures. This eliminates the filament leaking and stringing.
- A good printing speed can range between 40-60 mm/s
- Travel speed of 150-200 mm/s can be good.
- With different materials having their own melting time periods, you should test them by printing at lower speed first.
- Ensure to set the correct printing speed not too low or too high, because both of them can cause problems.
4. Keep Your Filament Moisture Free
In the 3D printing world, everyone is aware of the bad effects of filament moisture. When filament is exposed to open air, it absorbs the environmental moisture and this moisture turns into bubbles while printing at high temperatures.
These bubbles will get bursted and this bursting pushes the filament out of the nozzle causing Stringing and Oozing.
Sometimes, the filament moisture can also turn to steam and gets mixed with melted plastic material thereby onsetting the stringing problems.
Filaments such as Nylon and HIPS are worse when they are wet.
- Always store your filaments in an airtight container with desiccant packs that can keep the filament aloof from outside air and stop the moisture hitt.
- Prefer less moisture absorption materials like PLA, ABS rather than printing with Nylon.
- Dry the filament in a filament dryer for a good duration before printing. You can also use an oven but be careful while setting the temperature. Prefer low temperatures while drying with the oven.
5. Clean the Printing Nozzle
In 3D printing it is very common that filament residues will keep accumulating inside the nozzle as you print.
The residue will increase especially when you switch from high temperature filament printing to low temperature material like PLA, ABS.etc
For successful 3D printing results, always keep your nozzle blockage free. This significantly reduces the effect of stringing and oozing too.
- Clean the nozzle and remove all residues and dirt from it before printing.
- Use a metal wire brush to clean the nozzle.
- Clean the nozzle everytime immediately after a print. Blockages easily come out when they are in liquid state.
- Prefer cleaning the nozzle with Acetone when printing for a long time.
- Always clean the nozzle when you switch from one filament to another filament material.
All the above tips or methods should eradicate the stringing or oozing problem in your 3D printing.
These methods can be easy to implement or you may need to add some trial and testing to them. In any case they will help you to produce quality print results.
Experienced Project Engineer with a demonstrated history of working in the field of Product Design & Development industry in Mechanical Engineering. Skilled in 3D Printing and Re engineering Technologies with CATIA V5 , Materials Science, Finite Element Analysis (FEA), Mimics, ANSYS Workbench and Casting Simulation software. Strong engineering professional with a Master’s Degree focused in Industrial Metallurgy from PSG College of Technology, Coimbatore.