Orca Slicer pressure advance calibration

Pressure advance tunes how your printer handles the pressure that builds up in the nozzle, so corners come out crisp instead of bulged. When the nozzle slows for a corner, molten plastic keeps pushing from the pressure already in the melt, which over-extrudes the corner and leaves a blob. Pressure advance eases the pressure off just before the slowdown and adds it back on the way out, so the line stays even. Orca Slicer has a built-in test that finds the right value, and you save it to the filament.

What pressure advance does

Pressure advance controls extrusion pressure as speed changes, which mostly shows up at corners and at the start and end of a line. Set too low, and corners bulge and lines start with a blob. Set too high, and corners come out thin with gaps and the line ends early. The right value keeps the extruded line the same width all the way through a speed change, which is what gives sharp, clean corners at speed. It is called pressure advance on Klipper, linear advance on Marlin, and it is the same idea on both.

Before you start

A few things make the test reliable. Calibrate flow rate first, since the wrong flow amount muddies the result. Dry the filament, because moisture creates erratic extrusion that looks like a pressure problem and gives a random best value. Calibrate per filament, as PLA and PETG melt differently and need different values.

Firmware matters too. On Marlin, linear advance has to be enabled in the firmware first, and not every printer ships with it on, so if every test corner looks identical it is usually switched off. On a Bambu Lab machine, do not select the Flow calibration option during the test. When the test dialog opens it asks whether your printer is a direct drive extruder or a Bowden setup, because Bowden tubes need much higher values, so pick the one you have. Printing the test faster, around 100 mm/s or more, makes the difference between values easier to see.

Line method

The line method prints a set of lines, each at a different pressure advance value, and you pick the cleanest one. It is quick and easy to read.

1. Open the Calibration menu, choose Pressure Advance, and select the line method.
2. Choose direct drive or Bowden, then slice and print.
3. Look along each line. The best value is the line whose width stays even from end to end, with no bulge where it starts and a clean cutoff where it ends.
4. Enter that value as the pressure advance in the filament settings and save it.

Pattern method

The pattern method is adapted from Andrew Ellis’ generator and prints a pattern of cornered lines, which makes corner quality easy to judge. It is fast, but it leans on a good first layer, since the pattern is printed low.

1. In the Calibration menu, choose Pressure Advance, then the pattern method, and pick direct drive or Bowden.
2. Slice and print. The pattern uses your default and first-layer line widths and your first-layer and outer-wall speeds, so keep those sensible.
3. Examine the corners across the pattern and find the block with the sharpest corners and the fewest gaps, bulges or divots.
4. Save that value to the filament.

Tower method

The tower method prints a single tower whose pressure advance rises as it gets taller. It takes longer, but it does not depend on first-layer quality, which makes it a good choice when your first layer is not dialled in.

1. In the Calibration menu, choose Pressure Advance, then PA Tower, and pick direct drive or Bowden.
2. Slice and print the tower.
3. Look down the corners and mark the height where they come out cleanest, with no bulging.
4. Turn that height into a value with the formula: start value plus step times the height. With a start of 0 and a step of 0.002, a best height of 8 mm gives 0 plus 0.002 times 8, which is 0.016.
5. Enter that value in the filament settings and save it. The step is usually about 0.002 per millimetre for direct drive and higher for Bowden.

Adaptive pressure advance

For high-speed printers, Orca Slicer also offers adaptive pressure advance. Instead of one fixed value, it applies different pressure advance for different speeds and flow rates, which holds corner quality across the wide speed range a fast printer actually uses. It takes more setup than a single value, so it is worth it mainly once you are printing quickly and a single value no longer keeps every corner clean.

Saving and typical values

Pressure advance is saved to the material profile, so each filament keeps its own value. As a rough guide, Klipper direct-drive machines often land around 0.04 to 0.06, Marlin direct drive around 0.04, and Bowden setups much higher. Treat these as starting expectations, not targets, because the test result for your exact printer and filament is what counts. Recalibrate when you change filament type or switch between a direct drive and a Bowden setup. Marlin’s linear advance is less refined than Klipper’s pressure advance, so the gains are usually smaller on Marlin machines. After tuning, calibrating your seam and walls builds on the cleaner corners this gives you.

Frequently asked questions

What does pressure advance do in Orca Slicer?

It compensates for the pressure that builds up in the nozzle when the print speed changes, which is what causes bulged corners and blobby line starts. With it tuned, extrusion stays even through corners, so they come out sharp. Orca Slicer’s test finds the value and you save it to the filament.

Which pressure advance method should I use?

Use the line or pattern method for a quick result when your first layer is good, since they are fast to print and read. Use the tower method when your first layer is not reliable, because it judges corners up the height of a tower instead. On a fast printer, adaptive pressure advance holds quality better across speeds.

Why do all my pressure advance corners look the same?

On Marlin, that usually means linear advance is not enabled in the firmware, so the value has no effect. Check that it is switched on before trusting the test. Wet filament can also flatten the differences, so dry the spool first and run the test again.

What is a good pressure advance value?

It depends on your extruder. Klipper direct-drive machines are often near 0.04 to 0.06, Marlin direct drive near 0.04, and Bowden setups a good deal higher. These are only starting expectations. The value the test gives for your own printer and filament is the one to use.

Do I need to calibrate pressure advance for every filament?

Yes, ideally. Pressure advance is saved per filament, and different materials melt and flow differently, so a value that is perfect for PLA can leave PETG with bulged corners. Calibrate each filament type you print with for the cleanest results.