Extruder Tension: What it is and How to Calibrate it Properly

Extruder tension is an often overlooked and underestimated issue in 3D printing, yet it has a significant impact on print quality. If your printer's extruder is at the wrong tightness, it can potentially damage your printer. This article provides a simple guide on what extruder tension is, how it works, and most importantly, how to achieve the best tightness for the extruder.

What is Extruding Tension?

3D Printer Extruder
(Anycubic Kobra 2 dual metal gears in the direct extruder)

An extruder is a basic component of a 3D printer, responsible for gripping the filament and pushing it into the hotend, where the material is melted and extruded from a nozzle to form a 3D printed object. Extruder tension is a force applied to the filament by the extruder gear. The wrong extruding tension will cause filament grinding, over-extrusion and under-extrusion issues.

Some older and inexpensive printers have an extruder with a single gear combined with an idler gear. Currently, many 3D printers like Anycubic Kobra 2 feature dual metal gears in the extruder, enabling faster filament feeding into the hotend. This small difference can accelerate nozzle extrusion, thus enhancing printing speed.

How Does Extruder Tension Work?

3D Printer Extruder Type
(Left: Bowden extruder; Right: direct extruder; Image source: Daniel Ahlers)

Adjusting the extruding force is about tuning the tightness of the internal spring of the extruder. In general, you can fine-tune the screw or knob on the extruder. But the adjustment varies slightly depending on the type of extrusion system. For instance, a Bowden drive extruder is usually on one side of the Z-axis metal frame, while a direct extruder is integrated into the print head.

Proper extruder tension is essential for successful printing. The higher the tension, the tighter the extruder gears grip the filament. However, excessive tension can cause filament deformation or grinding. Conversely, insufficient tension may result in the gears slipping, lacking the force to grip the filament effectively, and thus making the filament not come out from the hotend.

When Should I Adjust Extrusion Tension?

3D Printer is Extruding
(The filament flows smoothly when the extrusion power is appropriate.)

As the printing time increases, the extruder screws may also become loose. When loading filament and feeding the hotend, you might need to adjust extrusion tension in the following situations.

When the tension is too high:

  • The extruder is making clicking noise.
  • Filament grinding issue happens.
  • The filament breaks.
  • The material gets entangled in the extruder.

When the tension is not enough:

  • The filament is not coming out.
  • The extruded plastic is too thin or uneven.

How to Properly Calibrate Extruder Spring Tension

Each printer may be slightly different in extruder tension calibration, but basically the same. You can simply loosen or tighten the screws on the extruder for adjustment. If you find the following instructions do not work, it is recommended to check the machine user manual or seek assistance from the manufacturer's support.

Bowden Extruder

3D Printer Bowden Extruder

Step 1: Heat your printer.

Step 2: Once the machine has reached the target temperature, load the material. Push the filament into the extruder. If your printer has a filament runout sensor, make sure the filament passes through it first and then enters the extruder.

Step 3: Ensure that the filament is properly going right into the Bowden tube. Keep pushing the material until the nozzle extrudes it.

Step 4: Keep feeding the printer with filament. And then loosen the adjustment screw of the extruder. Gradually tighten it to increase extruding power, and at the same time observe the status of the extruded filament. The extruding force is optimal when the filament flow becomes stable and appropriate.

Direct Extruder

3D Printer Bowden Extruder

The method is similar to that of a Bowden extruder. The slight difference is that, when loading the filament, you directly feed the extruder within the print head. Also, make sure the filament is getting into the tube during calibrating.