Under- or over-extrusion are common problems in 3D printing where the printer extrudes either too little (under-extrusion) or too much filament (over-extrusion). These issues significantly affect print quality as they can lead to thin layers, gaps, poor layer bonding, or excess material. Below, I explain the causes and solutions for incorrect filament feeding and how to properly adjust the extrusion settings in the slicer software.

Causes of under- or over-extrusion

There are several reasons why the printer does not extrude the filament properly. The most common causes are:

1. Incorrectly set extruder step value (E-Steps)

The step value of the extruder (E-Steps) determines how much filament the extruder extrudes for a given movement. Incorrectly set E-Steps lead either to under-extrusion (less filament than needed) or over-extrusion (more filament than needed).

2. Clogged or damaged nozzle

A partially clogged or worn nozzle can impair extrusion because the filament cannot flow properly through the nozzle. This usually leads to under-extrusion.

3. Incorrect filament diameter

If the filament diameter set in the slicing software does not match the actual diameter of the filament used, incorrect extrusion occurs. This can cause both under- and over-extrusion.

4. Incorrect flow rate (Flow Rate)

The flow rate (also called Flow) in the slicer software determines how much filament the printer should extrude. If this setting is incorrect, it can cause over- or under-extrusion.

5. Missing or blocked filament feed

If the filament feed mechanism, including the drive wheels, is dirty or worn, the filament cannot be properly transported into the nozzle. This usually leads to under-extrusion.

6. Inappropriate print speed

If the print speed is too high, the extruder may not be able to feed enough filament to keep up with the movement of the print head, leading to under-extrusion.

Solutions to fix under- or over-extrusion

1. Calibrate E-Steps (extruder steps)

The calibration of the E-Steps is an important step to ensure that the extruder feeds the correct amount of filament. Incorrectly set E-Steps are a common cause of incorrect extrusion.

This is how you calibrate the E-Steps:

  1. Mark filament: Mark the filament 120 mm above the extruder when it has been fully inserted into the extruder.

  2. Extrude 100 mm: Now extrude exactly 100 mm of filament via the menu or slicing software.

  3. Measure length: Measure the distance of the mark from the extruder. If the mark is more than 20 mm away (e.g., 30 mm), less filament was extruded than required (under-extrusion). If less distance was reached (e.g., 10 mm), it is over-extrusion.

  4. Adjust E-Steps: Adjust the E-Steps accordingly by increasing or decreasing the current E-Steps in the firmware or via the menu. Use the following formula:

    New E-Steps = Current E-Steps * (100 mm / actual extruded length)

  5. Repeat test: Repeat the process until the mark after extruding 100 mm has moved exactly 100 mm.

2. Clean or replace nozzle

A clogged or damaged nozzle often leads to under-extrusion because the filament cannot flow properly.

Nozzle cleaning:

  • Cold Pull: Heat the nozzle to extrusion temperature and perform a Cold Pull (see previous sections). This removes residues and clogs.
  • Needle cleaning: Use a cleaning needle to remove clogged particles in the nozzle. This is especially useful for small nozzle diameters like 0.4 mm.
  • Replace nozzle: If the nozzle is heavily worn or clogged, it should be replaced.

3. Check filament diameter

Make sure the filament diameter in the slicing software matches the actual diameter of the filament used. Most filaments have a diameter of 1.75 mm, but manufacturing tolerances can cause deviations.

How to measure the filament diameter:

  • Use a caliper to measure the actual diameter of the filament at several points.
  • Enter the average value in the slicing software (e.g., 1.74 mm instead of 1.75 mm) to optimize extrusion.

4. Adjust flow rate (Flow Rate)

The flow rate in the slicing software controls how much filament is extruded for a given movement. If the default flow rate of 100 % causes incorrect extrusion, it can be adjusted.

Adjusting the flow rate:

  • Increase the flow rate if you notice under-extrusion (e.g., to 105-110 %).
  • Reduce the flow rate if over-extrusion occurs (e.g., to 95-98 %).

Make sure to make only minor adjustments to fine-tune the extrusion amount.

5. Check and clean the extruder

Dirty or worn drive gears in the extruder cannot grip the filament properly, leading to uneven filament feeding. This is a common cause of under-extrusion.

How to clean and check the extruder:

  • Open the extruder: Turn off the printer and open the extruder to access the drive gears.
  • Clean drive gears: Use a brush or compressed air to remove dust or filament residues that could block the filament.
  • Check drive gears: Make sure the drive gears are not worn out. If they have become smooth, they should be replaced.

6. Reduce print speed

Too high a print speed can overload the extruder, so it cannot feed enough filament to extrude the required amount.

Adjusting print speed:

  • Reduce the print speed in the slicing software. For PLA, the recommended print speed is about 50-60 mm/s. For materials like TPU or PETG, you should print slower, e.g., 20-40 mm/s.
  • Also reduce the travel speed to ensure the print head moves in a controlled manner and the filament is extruded evenly.

7. Adjust extruder temperature

An incorrect extruder temperature can cause the filament not to melt properly (too cold) or to flow too much (too hot). Both can cause under- or over-extrusion.

Optimize extruder temperature:

  • For PLA, you should use a temperature of 190-220°C.
  • For ABS, the optimal temperature is 230-250°C.
  • For PETG, the temperature should be between 220-250°C.

If you notice under-extrusion, slightly increase the temperature (e.g., by 5-10°C) to help the filament flow better. For over-extrusion, lower the temperature accordingly.

Conclusion

Under- or over-extrusion can be fixed by a combination of calibration and fine-tuning. The key steps include calibrating the E-steps, adjusting the flow rate, checking the filament diameter, as well as regular cleaning of the extruder and the nozzle. These measures help optimize filament feeding and ensure your Creality K1 Max delivers precise and consistent print results.