How to fix Underextrusion

In this article you will find how to proceed if you are experiencing underextrusion







Underextrusion is the most common printing issue in 3D printing.  It consists of a lack of extruded material in the printed part that will show as missing layers or spongy prints.


What is Underextrusion and why it happens

Underextrusion, as the name states, happens when the hotend extrudes less plastic than desired. This issue affects directly the quality of the printed part. Making it look rough, incomplete, and weaker than usual. There are many factors that can make this happen.

underextrusion-gifWe recommend using BCN3D filaments with our 3D printers. The default BCN3D Stratos profiles for BCN3D filaments are tailored by our Lab to deliver the best quality and reliability on your prints, so if you find underextrusion in one of our filaments, it's possible that the filament itself needs to be dried, or there's a problem in the hardware. 


There are many ways to fix this issue, as there are many causes, you should check all the options to locate the issue and fix it effectively.

How to fix it 

As this issue has many different causes, troubleshooting the issue can be complex. Here's a list of all the causes and ways you can fix this. If one point does not do the trick, go to the next one. 

1. BCN3D Stratos version

stratos interface

BCN3D Stratos is constantly updated with new profiles that work better, pay attention to the release of new versions of BCN3D Stratos, and make sure to keep it updated.

To know how to download and install Stratos, visit this article: BCN3D Stratos.


2. Firmware

A printer with an old firmware can have some bugs that may cause underextrusion. To upgrade the firmware of the printer, Check out this articles depending on your model:

How to update the firmware (BCN3D Sigma)

How to update the firmware (BCN3D Sigmax)

How to update the firmware (Epsilon Series / Sigma Series)


3. Material


To avoid Underextrusion, we recommend the default profiles for BCN3D Filaments in Stratos, those profiles are specially made to ensure a safe print, ensuring the best print quality. If you are experiencing underextrusion with our materials and using our default profiles, go to the next point.


If you are using custom profiles or filaments from a different brand, note that there are some factors that can also cause underextrusion, such as excessive printing speed, low printing temperatures, or a bad retraction configuration. Here are some tips you can use to prevent this from happening. 


Tip: If you use materials that are not from BCN3D, feel free to contact the manufacturer to get a printing profile for your filament, they know their filaments more than anyone else.


Printing Temperature: Normally if you find underextrusion, the first thing to look at is the printing temperature. Most 3D printing filaments show a range of temperatures in the same spool. To find the right temperature , you can print the following test and change the printing temperature until you find the one that has the best quality:

Temperature test object by cyberbsd

Start from the higher temperature and lower it in 5ºC steps while it's getting printed, write down what temperature goes best with that material. 


Printing Speed: If the printing speed is too high, you'll notice that the hotend is not able to extrude enough material on the printed part. Speeds of 50mm/s are generally good for ABS, PLA, and PET-G, while other filaments may require slower speeds. 


Retraction Settings: Retraction is a feature in which the filament is pushed out of the nozzle a bit to prevent oozing during a travel. If the number of retractions, retraction distance, or retraction speed is excessive, you might find gaps appearing on the walls of the print or experiencing hotend clogs. 


Note: For more information about how to use BCN3D Stratos, visit the next article: BCN3D Stratos Introduction


Sometimes,  underextrusion will appear even when printing two exact print jobs with the same materials and configurations. Take into account that underextrusion also depends on the filament and room humidity, room temperature, and manufacturing defects. 

To prevent other issues with our filaments, check the following tips and tricks articles for each material: 

Standard Technical Composites


4. Bowden tubes

bowdens Cropped

The bowden and the filament are in constant friction. Occasionally an excess of friction can stop the filament and could cause underextrusion. Check the bowden and if it is bent or has a bad shape, change it for a new one.


If this is the case, contact us or your reseller of choice to get a new bowden tube.

Get in contact with us

Find your local reseller


5. Bad cooling

cooler fan new Cropped

An excess of temperature in the printing head can cause a clog in the hotend, this will cause a gradual underextrusion along with the print until no filament is extruded. Check if the cooler fans are clean and use a vacuum cleaner or a brush to ensure that nothing is blocking the fan. To check if the fans work properly, follow the next articles:


How to check the operation of the cooler fan (BCN3D Sigma)

How to check the operation of the cooler fan (BCN3D SigmaX)

How to check the operation of the cooler fan (Epsilon Series)

How to check the operation of the cooler fan (Sigma Series)


Note: In some cases, room temperature can influence this, especially with PLA. Check that the room temperature is not over 25ºC and there's correct airflow in the room. 


6. Hotend

BCN3D_Epsilon_3D_Printer_hotend_06X-jpg Cropped

A constant underextrusion throughout the piece shows that the issue can be located in the hotend, specifically if you use different materials in the same hotend. If you are using multiple material types, the hotends can clog over time; you should always clean the hotend with nylon every time you change material types.


Check these articles about how to clean the hotends:

How to clean the hotend (BCN3D Sigma)

How to clean the hotend (BCN3D Sigmax)

How to clean the hotend (Epsilon Series)

How to clean the hotend (Sigma Series)

How to unclog a hotend


If the problem persists, probably the hotend is damaged or clogged severely, try to swap the hotends and print, if the problem moves, you will need to unclog the hotend or swap it out for a new one. The following articles have information about it:

How to change the hotend (BCN3D Sigma)

How to change the hotend (BCN3D Sigmax)

How to change the hotend (Epsilon Series)

How to change the hotend (Sigma Series)


Usually, if the hotend is burnt or damaged, the extruder board has a problem, go to the next section to find more information about this.

Warning! Hardened steel hotends shouldn't be used for non-abrasive materials like PLA, ABS, PET-G, TPU, etc. For non-abrasive, plain materials, it's best to use brass-tipped hotends. 


7. Extruder Board

eboard Cropped

This component controls the hotend temperature and the fans function. If the extruder board doesn't work properly, it can lead to random underextrusion and overheating issues during the print job.


To check that the problem is here, you can swap the extruder boards, if the problem moves to the other printing head, you will need to swap out the extruder board in question for a new one.


For more information about how to swap and change the extruder boards, see the next articles:

How to change the extruder board (BCN3D Sigma)

How to change the extruder board (BCN3D Sigmax)

How to change the extruder board (Epsilon Series)

How to change the extruder board (Sigma Series)


8. Extruder motor

check extruder Cropped (1)

If the extruder motor can't push the filament correctly, the result will be underextrusion. Sometimes this is accompanied by a repetitive clicking noise.


To fix or change the extruder motor, check the next guides:

How to disassemble and check the extruder motor (BCN3D Sigma)

How to disassemble and check the extruder motor (BCN3D SigmaX)

How to check the operation of the Bondtech extruders (Epsilon Series)

How to check the operation of the Bondtech extruders (Sigma Series)


If the problem continues, swap the extruder drivers and check if the problem moves from side. These articles will help you with this:

How to change the extruder driver (BCN3D Sigma)

How to change the extruder driver (BCN3D Sigmax)

How to change the extruder driver (Epsilon Series)

How to change the extruder driver (Sigma Series)



If you still experience underextrusion issues, get in contact with our support team by filling this form.

Forum community 

The repair didn’t go as planned? Check out our forum community for troubleshooting help.


It's important to keep your printer in good shape to make the most out of it. In this chart, you can find a list of the extruder maintenance procedures and how frequently these should be done. 

Maintenance Plan (BCN3D Sigma)

Maintenance Plan (BCN3D Sigmax)

Maintenance Plan (Epsilon Series)

Maintenance Plan (Sigma Series)


bcn3d-recycle  Take your e-waste to a certified recycler. Check how we do it in BCN3D.



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