Under-extrusion is a common issue in 3D printing, where the printer fails to extrude enough filament during a print. This leads to gaps, weak layers, and poor print quality. If not addressed, under-extrusion can ruin a print and waste materials, time, and effort. Fortunately, understanding the underlying causes of under-extrusion and how to fix them can help you get back to smooth, reliable printing.
In this article, we’ll explore the possible causes of under-extrusion, offer troubleshooting tips, and guide you through the necessary steps to resolve this issue and improve your 3D printing experience.
What is Under-Extrusion in 3D Printing?
Under-extrusion occurs when the 3D printer fails to extrude the right amount of filament, leading to insufficient material being deposited onto the print bed. This can result in thin or missing layers, gaps in the print, or poor adhesion between layers. In extreme cases, under-extrusion can cause complete print failures.
Common Causes of Under-Extrusion
1. Clogged or Partially Blocked Nozzle
One of the most common causes of under-extrusion is a clogged or partially blocked nozzle. As filament passes through the nozzle, debris, dust, or filament residue can accumulate and restrict the flow of material. Even a slight clog can lead to inconsistent extrusion.
- How to fix:
- Cold Pull: Heat the nozzle to the printing temperature, then lower the temperature and manually pull the filament out. This can help clear small blockages.
- Nozzle Cleaning: If the clog persists, remove the nozzle and use a needle or nozzle cleaning tool to remove any blockage. You can also use a cleaning filament or soak the nozzle in acetone (for ABS) or isopropyl alcohol (for PLA) to dissolve any buildup.
- Replace the Nozzle: If cleaning doesn’t resolve the issue, it may be time to replace the nozzle, especially if it has been worn out by abrasive filaments.
2. Incorrect Extruder Tension
The extruder is responsible for pushing filament into the hotend, and if the extruder tension is too loose or too tight, it can cause under-extrusion. If the drive gear isn’t properly gripping the filament, it won’t feed correctly, leading to gaps in the print.
- How to fix:
- Adjust Extruder Tension: Check the extruder tension and adjust it to ensure the drive gear has a firm grip on the filament. Be careful not to overtighten, as this can cause filament deformation.
- Inspect the Drive Gear: Make sure the extruder gear is clean and free from filament buildup. If it’s dirty, clean it with a brush or compressed air.
3. Filament Issues
Inconsistent or low-quality filament can cause under-extrusion, especially if it is brittle, tangled, or incorrectly sized. Moisture absorption by filament can also cause extrusion problems, leading to inconsistent flow and poor print quality.
- How to fix:
- Check for Tangling: Ensure that the filament spool is free from tangles and is properly mounted on the spool holder. A tangled spool can cause uneven feeding, which leads to under-extrusion.
- Dry the Filament: Filament like PLA, ABS, and nylon can absorb moisture from the air, which results in bubbles or inconsistencies during extrusion. If you suspect moisture, dry the filament in an oven or filament dryer before use.
- Check the Diameter: Measure the filament diameter using calipers to ensure it’s consistent. A filament that is too thick or thin can cause under-extrusion as the printer cannot compensate for size variations.
4. Incorrect Temperature Settings
If the extruder temperature is too low, the filament may not melt properly, leading to under-extrusion. Filament types have specific temperature ranges, and printing outside of these ranges can cause inconsistent flow.
- How to fix:
- Increase Extruder Temperature: Check the recommended temperature range for the filament you are using and adjust the extruder temperature accordingly. For example, PLA typically prints well at around 190°C to 220°C, while ABS requires temperatures between 230°C to 250°C.
- Check the Heated Bed: Make sure the heated bed is at the correct temperature, especially for materials like ABS, which need higher bed temperatures to prevent warping and improve adhesion.
5. Inconsistent or Low Flow Rate
The flow rate setting controls how much filament is extruded during the print. If the flow rate is set too low, it can lead to under-extrusion, even if everything else is working correctly.
- How to fix:
- Adjust the Flow Rate: Use your slicing software to adjust the flow rate setting. This is usually set to 100% by default, but you can slightly increase the flow rate by 5-10% if you’re experiencing under-extrusion.
- Check Slicer Settings: Ensure that your slicer software is correctly calibrated and that the extrusion multiplier (flow multiplier) is set appropriately for the filament you are using.
6. Blocked or Damaged Bowden Tube (For Bowden Printers)
If your 3D printer uses a Bowden tube to guide filament from the extruder to the hotend, a blocked or damaged tube can cause resistance, leading to under-extrusion. The tube may become kinked, bent, or clogged over time, restricting the flow of filament.
- How to fix:
- Inspect the Bowden Tube: Check the Bowden tube for any bends, blockages, or damage. If it’s obstructed, carefully remove the filament, inspect the tube, and clear any debris or blockages.
- Replace the Bowden Tube: If the tube is damaged or worn out, replace it with a new one. Make sure the tube is cut to the proper length and fits securely in the extruder and hotend.
7. Wrong Print Speed or Layer Height Settings
If your printer is moving too fast or the layer height is set too high, the extruder may struggle to keep up with the demand for filament, leading to under-extrusion.
- How to fix:
- Reduce Print Speed: Slower print speeds can allow the extruder to keep up with the material flow and ensure better adhesion between layers. Start by reducing the print speed by 10-20% and monitor the results.
- Adjust Layer Height: If the layer height is too large for the nozzle size, the extruder may not be able to keep up with the flow rate. Try reducing the layer height to match the nozzle size (e.g., using a 0.2 mm layer height with a 0.4 mm nozzle).
8. Electrical or Mechanical Issues
Occasionally, under-extrusion can result from a mechanical failure, such as a stepper motor issue or a problem with the extruder gear. Electrical issues can also prevent the extruder from operating at full capacity.
- How to fix:
- Check the Stepper Motor: Inspect the extruder stepper motor for any signs of malfunction or wear. Ensure that the motor is properly connected and functioning. If the motor is overheating or malfunctioning, it may need to be replaced.
- Examine the Drive Gear: Look for any issues with the extruder drive gear. If it’s worn out or slipping, replace it with a new one.
Final Thoughts
Under-extrusion is a frustrating but solvable issue in 3D printing. By systematically troubleshooting common causes, such as clogged nozzles, incorrect temperature settings, or filament issues, you can resolve under-extrusion and improve the quality of your prints.
Start by checking your filament, nozzle, and extruder settings, and proceed through the other potential issues outlined above. Once you’ve found and addressed the cause, your prints will improve significantly, resulting in better quality, stronger prints, and fewer wasted materials.