What Is Pressure Advance / Linear Advance and How Do You Tune It?

Bulging corners during fast prints, small gaps at the start of straight lines, and material build-up during sudden direction changes are familiar problems for most users. The common solution to these issues is usually a setting called pressure advance. In Klipper firmware it goes by this name, while on the Marlin side it is known as Linear Advance; both solve the same physical problem.

Where Does the Problem Come From?

As the extruder pushes material, molten plastic builds up pressure inside the nozzle. When the printer stops, this pressure does not disappear immediately — the nozzle continues to ooze material for a moment. When accelerating, the pressure takes time to build up. As a result:

• Excess material accumulates at corners, causing bulging
• A gap remains at the start of a straight line because extrusion is delayed
• Fine threads (oozing) appear at the ends of lines

What Does Pressure Advance Do?

This feature adjusts how much material the extruder pushes based on the print head’s current speed. In other words, the printer reduces flow before decelerating and increases it before accelerating. This way, the pressure inside the nozzle adapts more closely to the head’s speed, and corner bulging as well as start-of-line gaps are noticeably reduced. One important point: this setting actually corrects flow dynamics rather than hiding poor calibration.

Tuning with the Test Tower

The most practical method is to use the test pattern provided by the firmware. In Klipper, you use the TUNING_TOWER command to print a tower that incrementally changes the pressure advance value during the print. On the Marlin side, a similar Linear Advance test pattern is available. Once the tower is complete, you identify the height where the corners look cleanest and bulging is minimal, then save the corresponding value to your firmware.

Typical Values and Warnings

In Bowden setups the value tends to be higher due to the tube length; in direct drive setups it is generally much lower. Keep in mind that every spool — and even every material — can behave slightly differently. Also, pressure advance is not a magic fix; switching to this setting without first completing flow and temperature calibration will give incorrect results. Build the foundation first, then move on to this fine-tuning.

Fine calibrations like these take time and experience. If you would prefer to have your parts produced on properly calibrated machines, you can check our production pricing and leave your project with us — we’ll handle the technical details.