How do I calibrate a new filament in OrcaSlicer or Bambu Studio?

The order, and why it matters

Each test builds on the ones before it, so run them in this order for every new filament (OrcaSlicer's own guide gives the same order):

1. Temperature: the hottest and coolest the filament prints well at.
2. Max volumetric speed: how much plastic per second your hotend can melt for this filament.
3. Pressure advance (Bambu Studio calls it Flow Dynamics): how the extruder makes up for pressure in the nozzle when speeding up and slowing down, for sharp corners.
4. Flow ratio (Flow Rate in Bambu Studio): how much plastic comes out compared with what the slicer asks for.
5. Retraction: how far the filament is pulled back on travel moves, against stringing.

Pressure advance and flow ratio affect each other a little. If the flow ratio changed a lot, run a quick pressure advance test again. The tests also assume the extruder itself is calibrated in the printer's firmware (e-steps or rotation distance).

Where the tests are

• OrcaSlicer: the Calibration menu. Each test opens as a new project with the test model; when you're done, start a new project to leave calibration mode.
• Bambu Studio: the Calibration tab, with Flow Dynamics, Flow Rate, Max Volumetric Speed, Temperature and Retraction.

Pick the printer, nozzle and the filament profile you're calibrating before starting: the tests start from that profile's values. After each test, put the result into the filament profile and save it, so the next test uses it.

Do Bambu Lab printers need it?

Often not. Bambu Studio says flow dynamics calibration is usually unnecessary: the printers calibrate it themselves (results are saved on the printer), and Bambu's own filaments come pre-tuned. It suggests calibrating again when you switch to a new brand or type of filament, the filament is damp, the nozzle is worn or replaced, or you've changed the max volumetric speed or print temperature. Flow rate calibration is mainly for filaments that still show problems after that, and for foaming filaments like LW-PLA.

Printing OrcaSlicer's flow ratio or pressure advance tests on a Bambu printer? OrcaSlicer's guide says to switch off the printer's own Flow calibration option when you send the print, or it overrides what you're testing.

The tests, one by one

1. Temperature tower

Blocks printed at different temperatures, each labelled. Look for the block with the least stringing, good layer bonding, clean overhangs and bridges. If several look good, take the middle of the range, or the upper end if you print fast.

2. Max volumetric speed

A print that asks for more and more plastic per second as it goes up, until the hotend can't keep up and the walls fail. Use a value 10–20% below the result. Don't trust the number on the spool: some makers overstate it.

3. Pressure advance (Flow Dynamics)

OrcaSlicer offers three ways, each for direct-drive and Bowden extruders:

• Line: lines printed with rising values; pick the most even line. Quick, but it depends on a perfect first layer, so turn on bed levelling.
• Pattern: corner patterns; pick the sharpest corners. Several tests fit on one plate.
• Tower: the value rises with height, one step per millimetre. Measure the height of the best corner and work it out: start + step × height (for example 0 + 0.002 × 8 = 0.016). It doesn't depend on the first layer.

On Marlin printers, Linear Advance must be enabled in the firmware (the M900 command) for this to do anything; not all printers have it on.

4. Flow ratio (Flow Rate)

A set of blocks, each with a slightly different flow, printed with a smooth top surface. Pick the block with the smoothest top: no gaps between lines (too little) and no ridges or rough patches (too much). In OrcaSlicer, the recommended YOLO test adds the block's number to your current ratio, for example 0.98 + 0.01 = 0.99. The older two-pass test multiplies instead: ratio × (100 + number) ÷ 100.

5. Retraction

A tower with retraction length rising with height (OrcaSlicer: 0 to 2 mm for direct drive, 1 to 6 mm for Bowden). The best length is the shortest one with a clean tower. The defaults usually work: for PLA and ABS on a direct drive printer, 0.2 to 0.4 mm is often enough.

Before and after

• Dry the filament first if it's been out for a while: damp filament strings and pops whatever the settings.
• Check the sliced test in the G-code viewer before printing: the right printer, the expected time and filament, and a first layer where you expect it.
• Once a filament is tuned, the print cost calculator turns its price per spool into the cost of each print.