Shenzhen Alu Rapid Prototype Precision Co., Ltd.

Pressure Advance (sometimes called Linear Advance in Marlin firmware) is a feature in modern 3D printer firmwares (Klipper, Marlin, Klipper-based systems like Fluidd/Mainsail, PrusaSlicer with Prusa firmware, etc.) that dramatically improves cornering and retraction performance, especially with bowden-extruder printers, but it also helps direct-drive setups.

The Problem It Solves

In a normal extruder, when the printer suddenly changes speed (e.g., at sharp corners, start/stop of perimeters, or when retracting), there is a slight delay between:

a.The extruder motor commanding filament in/out and

b.The actual molten plastic exiting the nozzle.

This delay happens because the filament is compressible and there is pressure built up inside the melt zone of the hotend.

Result without correction:

a.Oozing/Strings at corners

b.Blobbing/Bulging at the start of a new line

c.Over-extrusion right after a retraction

d.Under-extrusion right before a retraction

e.Poor sharp corner quality (rounded or with “ears”)

How Pressure Advance Works

Pressure Advance predicts these pressure changes and temporarily adjusts the extruder speed in advance of acceleration/deceleration events.

a.When the print head accelerates (e.g., leaving a corner), the firmware pushes a tiny bit of extra filament ahead of time to build pressure quickly.

b.When the print head decelerates (e.g., approaching a corner), the firmware pauses or even slightly reverses the extruder early to relieve pressure before the move actually slows down.

The net effect is that the actual flow of plastic out of the nozzle stays perfectly in sync with the actual XY motion, even during rapid speed changes.