Flow Rate vs Flow Dynamics in Bambu Studio: How to Calibrate

Bambu printers do a good job out of the box, but if you're seeing blobs, gaps or rough walls, two calibrations make a big difference: flow dynamics and flow rate. Here's what each does and how to run them manually in Bambu Studio.

What they do

Think of the nozzle as the opening of a toothpaste tube.

• Flow dynamics (the K factor) handles the timing. There's a delay when you start squeezing and when you stop. Calibrating teaches the printer when to "pre-squeeze" and ease off, so you don't get blobs, gaps or weird corners.
• Flow rate handles the amount. Too hard and you get a glob, too soft and barely anything comes out. Calibrating gives you accurate walls, solid layers and a clean finish.

In Bambu Studio, the K factor lives in the Device tab and the flow ratio in the filament profile. Yes, it's annoying they aren't together.

Before you start: custom filament profiles

Using a built-in profile? Skip this. If you've made your own, create a custom filament so the calibration can see it: Create new → choose vendor and type → Copy current filament preset → select your printers → Create.

A1 and X1 printers also offer automatic calibration, but it can be inaccurate, so I recommend doing it manually.

Flow dynamics calibration

1. Go to the Calibration tab → Flow Dynamics → Manual calibration.
2. Select your nozzle size, plate type and filament.
3. Choose the line method and set the value step to 0.001 for the most precise result.
4. Print, then pick the line that's most consistent, with no over- or under-extrusion. Mine came out at K = 0.033.

5. In the Device tab, click the filament, choose your material and select the new profile. You can edit or delete results later under Manage result.

Flow rate calibration

1. Choose Flow Rate → Complete calibration, with the same nozzle, plate and filament.
2. The printer prints a set of numbered rectangles.

3. Pick the one with the smoothest top surface (I find looking works better than feeling) and select its number.
4. Save it to a new filament profile, or note the number and add it to your existing preset. An extra fine-tuning pass is optional; I find the first is good enough.

Tips

• If your printers have identical hardware, calibrate once per filament on one machine. The results carried over to all of mine.
• Different colours from the same brand usually share settings, but test it, since it depends on the brand's consistency.
• Re-calibrate when you try a new brand, when surface finish really matters, after hardware changes, or when you notice print issues.
• Calibrating wet filament gives misleading results, so dry it first.

What I use

• PCBWay: professionally printed parts with no calibration needed ($5 credit with this link)

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More guides

Scrubbler Nozzle Wiper for Bambu Lab P1S: Install Guide and Fix Bambu Lab Prints Not Sticking? How to Fix Bed Adhesion How to Tell If Filament Is Wet, and the Best Ways to Dry It

Common questions

What is the difference between flow rate and flow dynamics?

Flow dynamics (the K factor) controls the timing of extrusion, so you don't get blobs, gaps or bad corners. Flow rate controls the amount of filament, for accurate walls, solid layers and a clean finish.

How do I calibrate flow dynamics in Bambu Studio?

Go to Calibration > Flow Dynamics > Manual calibration, choose the line method with a 0.001 step, print, and pick the most consistent line. Then assign the new K value to the filament in the Device tab.

How do I calibrate flow rate in Bambu Studio?

Choose Flow Rate > Complete calibration with the same nozzle, plate and filament, then pick the numbered rectangle with the smoothest top surface and save it to your filament profile.

Do I need to calibrate every colour of filament?

Different colours from the same brand usually share settings, but test it. Re-calibrate for a new brand, after hardware changes, or when you notice print issues.

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