Belt Tension and Linear Advance: Two Quick Print Fixes

Wavy walls and rounded corners often come from two causes: belts and extrusion pressure. Here is how to check both.

Belt tension

Loose belts cause ghosting, wavy edges, layer shifts and dimension errors. Belts should be taut, but not tight like a guitar string. A light pluck should give a clear, low note. Also check that the pulley screws are tight, then tighten the belt gently and test again.

What linear advance does

When the printer speeds up or slows down, pressure in the nozzle lags behind. Linear advance (called pressure advance in Klipper) compensates for this, which gives sharper corners and more even lines.

How to tune it

Print a linear advance calibration pattern, find the line where corners are sharpest without gaps, and set that K value in your firmware (Marlin uses the M900 command). Save the setting. The best value depends on your extruder, hot end and material, so tune it again when you change filament type.

This is general guidance. Always follow your printer manufacturer's instructions.

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