What is Linear Advance in 3D Printing: Explanation and Use Cases

In 3D printing, linear advance is a technique that adjusts the extrusion flow based on the print head's speed to keep the filament pressure steady. It helps prevent issues like blobs or gaps by predicting and compensating for delays in filament flow during acceleration and deceleration.

How It Works

Imagine pushing toothpaste out of a tube while moving your hand faster or slower. If you suddenly speed up, the toothpaste might not come out evenly right away because of pressure inside the tube. Similarly, in 3D printing, when the print head speeds up or slows down, the filament inside the nozzle takes a moment to catch up or slow down, causing uneven extrusion.

Linear advance works by predicting these changes in speed and adjusting the extrusion amount ahead of time. It increases extrusion slightly before speeding up and reduces it before slowing down, keeping the pressure inside the nozzle steady. This results in smoother lines and better print quality without blobs or gaps.

Example

This example shows a simple simulation of linear advance calculation in Python. It calculates the adjusted extrusion amount based on current speed and a linear advance factor.

python

def linear_advance(extrusion_length, speed, k_factor):
    """Calculate adjusted extrusion length using linear advance."""
    adjusted_extrusion = extrusion_length + k_factor * speed
    return adjusted_extrusion

# Example values
extrusion_length = 5.0  # mm
speed = 50.0            # mm/s
k_factor = 0.02         # linear advance factor

adjusted = linear_advance(extrusion_length, speed, k_factor)
print(f"Adjusted extrusion length: {adjusted:.2f} mm")

Output

Adjusted extrusion length: 6.00 mm

When to Use

Use linear advance when you notice print quality issues caused by inconsistent extrusion during speed changes, such as blobs at corners or gaps in lines. It is especially helpful for printing detailed parts with many speed changes or sharp corners.

Many modern 3D printers and firmware support linear advance settings. Calibrating the k_factor for your specific printer and filament can greatly improve surface finish and dimensional accuracy.

Key Points

• Linear advance controls filament pressure by adjusting extrusion based on speed.
• It prevents common print defects like blobs and gaps during acceleration or deceleration.
• Requires calibration of a factor (k-factor) specific to your printer and filament.
• Improves print quality, especially on detailed or fast prints.

Key Takeaways

Linear advance adjusts extrusion to keep filament pressure steady during speed changes.

It helps eliminate blobs and gaps caused by delayed filament flow.

Calibration of the linear advance factor is essential for best results.

Use it for prints with many speed changes or sharp corners to improve quality.