Pressure Advance in FDM: Get Cleaner Corners Without Over-Tuning

Why do corners sometimes get messy?

In FDM printing, the extruder pushes filament through the nozzle. When the print head accelerates or slows down, its movement changes faster than the pressure in the molten filament can adjust. This can result in too much material at a corner, a small bulge, or uneven lines where the printing direction changes.

Pressure advance attempts to compensate for this delay by adjusting filament feed in relation to the print head’s speed. The feature goes by different names: Klipper uses *Pressure Advance*, while Marlin calls its equivalent *Linear Advance*. They address related problems, but their settings and calibration methods are not directly interchangeable. (klipper3d.org)

What the setting can—and cannot—do

Well-tuned compensation can reduce material buildup at corners and make lines more consistent when speed changes. However, it is not a universal fix for every uneven print. Incorrect flow, improper extruder calibration, fluctuating temperature, or mechanical play can cause similar symptoms.

So don’t start with Pressure Advance if the basic settings are still uncertain. Klipper’s documentation recommends setting the extruder’s rotation distance and the nozzle temperature before calibration. The value is also affected by the printer, extruder, nozzle, and filament—even different filament variants may need different values. (klipper3d.org)

A practical calibration sequence

1. Check the basics. Make sure the extruder feeds the correct amount of filament and that the temperature is suitable for the material. Also make sure the nozzle is clean and that the print does not show obvious under- or over-extrusion. 2. Choose the method that matches your firmware. Follow the instructions for your specific printer and firmware. Klipper has its own calibration guide; Marlin uses Linear Advance and a K value when the feature is enabled. (klipper3d.org) 3. Print the test with stable settings. Don’t change temperature, flow, and speed at the same time—it will be difficult to tell what improved or worsened the result. 4. Evaluate several corners and lines. Look for a setting where the corners are well-defined without the lines before or after them looking thin or interrupted. Follow the test instructions to convert that setting into a value. 5. Save the value in the right profile. Note the printer, nozzle, filament, and relevant print conditions. If you change material or alter the filament path, it may be worth testing again.

Test patterns and commands differ between firmware versions and machines. So don’t treat a value from another printer as the definitive answer. Klipper’s method uses a test print that lets you compare the effects of different settings, while Marlin’s documentation describes how to calibrate its K value. (klipper3d.org)

Signs that the value needs another look

• Corners still bulge: the compensation may be too low, but first check for over-extrusion and temperature issues.
• Lines become thin after corners or start unevenly: the value may be too high, or there may be another filament-feed problem.
• Results vary between spools: the material’s properties may affect which value works best.
• Calibration seems random: check that the test is printed at the same temperature and that the mechanics and extruder feed are stable.

Change only one thing at a time, and compare with a print without compensation if you’re unsure whether the feature is helping. The goal is not a particular high value or maximum speed, but cleaner transitions without new signs of under-extrusion.

Pressure Advance is a refinement, not a shortcut

The feature is most useful when the printer is already working reliably and the problem clearly occurs during acceleration and at corners. When set correctly, it can improve the appearance of corners, but it does not replace correct flow, temperature, or extruder calibration. Start with the instructions from the manufacturer or firmware project, run a controlled test print, and save the result with the filament profile.