How To Fix Under Extrusion
When working with 3D printers, one of the most frustrating issues that can appear is under extrusion. This problem occurs when the printer is not pushing enough filament through the nozzle, leading to gaps in prints, weak layers, or missing details. For hobbyists, students, and professionals who rely on reliable printing quality, knowing how to fix under extrusion is essential. It can have multiple causes, from incorrect slicer settings to clogged nozzles, and learning how to diagnose and solve it will improve both the quality and efficiency of every print. Instead of letting failed projects slow you down, exploring the practical steps and methods to solve under extrusion will help ensure strong, smooth, and consistent 3D prints.
What is Under Extrusion?
Under extrusion happens when your printer fails to supply enough melted filament to match the required output defined in the slicer. This results in gaps between layers, uneven surfaces, weak adhesion, or even complete breaks in prints. Recognizing it early is important because prolonged printing with under extrusion can waste time and materials while producing unusable objects.
Common Signs of Under Extrusion
- Visible gaps between printed lines or layers.
- Thin walls that should be thicker according to the design.
- Prints that are weak or easily breakable.
- Clicking or grinding noises from the extruder motor.
- Incomplete infill patterns.
Main Causes of Under Extrusion
Understanding the main causes will make fixing under extrusion much easier. The issue can stem from mechanical, software, or material-related problems. By testing each potential factor, you can pinpoint the root cause and apply the right fix.
1. Filament Issues
Sometimes the filament itself is the reason for under extrusion. Filament that is too brittle, swollen, tangled, or wet can create inconsistent feeding. Moisture in particular causes bubbling inside the nozzle, restricting flow and reducing extrusion.
2. Nozzle Clogs
Partial blockages in the nozzle can prevent smooth extrusion. Dust, burnt filament, or poor-quality materials can leave residue inside, leading to inconsistent output. Even minor debris can disrupt the flow and cause under extrusion.
3. Incorrect Slicer Settings
If your slicer is misconfigured, it may demand too little material or use the wrong extrusion multiplier. Incorrect layer height, flow rate, or line width settings can all result in prints that appear under extruded.
4. Extruder Tension Problems
The extruder gear needs the right pressure to grip the filament and push it smoothly into the hot end. If the tension is too loose, the gear will slip. If it is too tight, it can grind into the filament and damage it.
5. Temperature Settings
Filament requires specific temperature ranges to melt properly. Printing at too low a temperature means the plastic will not flow freely, resulting in insufficient extrusion. On the other hand, overheating can cause degradation and clogs.
6. Bowden Tube or PTFE Issues
A damaged or poorly seated Bowden tube can cause resistance in filament movement. Cracks, wear, or misalignment will make extrusion inconsistent and contribute to under extrusion.
How to Fix Under Extrusion
Now that the possible causes are clear, the next step is applying practical solutions. Each fix depends on identifying what is wrong with your printer, filament, or settings. Here are the most effective ways to fix under extrusion and restore smooth printing.
Check and Replace Filament
Start by examining your filament spool. If it looks tangled, brittle, or moist, replace it with fresh filament. Always store spools in dry containers to avoid moisture absorption. High-quality filament is less likely to cause extrusion problems, so consider testing with a reliable brand.
Clean or Replace the Nozzle
A clogged nozzle is one of the most common culprits. To clean it, try heating the nozzle and using a cleaning filament or a cold-pull method. For stubborn clogs, you may need to fully remove the nozzle and clean it with a fine needle. If the nozzle is too worn, replacing it is often the easiest fix.
Adjust Slicer Settings
Check your extrusion multiplier, line width, and flow rate in the slicer software. Increasing the flow rate slightly can often solve under extrusion if the printer is mechanically fine. Also, ensure the layer height is not too high compared to the nozzle diameter, as this can demand more filament than the nozzle can supply.
Set Proper Extruder Tension
Open your extruder assembly and inspect the gear tension. If it is too loose, tighten the adjustment screw slightly until the gear grips the filament securely. Be cautious not to overtighten, as this may grind or deform the filament surface.
Calibrate the Extruder Steps (E-Steps)
Calibrating the extruder steps ensures the motor pushes the correct length of filament. Use a simple test by marking a filament length, commanding the printer to extrude, and measuring how much actually feeds through. Adjust the E-steps in firmware if necessary to achieve accurate extrusion.
Check Printing Temperature
Verify that you are using the recommended temperature for your filament. For example, PLA usually prints between 190°C and 220°C, while ABS needs higher ranges around 230°C to 250°C. If under extrusion persists, increase the temperature slightly to improve filament flow.
Inspect the Bowden Tube
Look for cracks, wear, or loose fittings in your Bowden tube or PTFE liner. Replace any damaged parts and make sure the tube is firmly seated inside the extruder and hot end. This will reduce resistance and allow filament to move more smoothly.
Preventing Future Under Extrusion
Fixing the issue once is helpful, but prevention will save you time and frustration in the long run. By following good practices and regular maintenance, you can minimize the risk of under extrusion.
Best Practices for Prevention
- Always use high-quality, dry filament.
- Store spools in airtight containers with desiccant.
- Regularly clean the nozzle and extruder gear.
- Calibrate extrusion steps periodically.
- Check slicer settings for each filament type.
- Inspect mechanical parts like the Bowden tube and gears frequently.
Under extrusion is one of the most common and frustrating 3D printing problems, but it is also one of the most solvable. By learning how to fix under extrusion, you can improve print quality, reduce wasted materials, and enjoy smoother printing experiences. Whether the issue comes from clogged nozzles, faulty filament, or incorrect slicer settings, the solutions are usually straightforward once you know what to look for. Maintaining your printer, calibrating settings, and keeping your filament in top condition will help you avoid under extrusion and achieve consistent, reliable prints every time.