Flow Rate

About this Calibration

Flow Rate Calibration measures the ratio of expected to actual extrusion volumes. This ratio is normally stable and the default setting works well in Bambu Lab printers and official filaments as they were pre-calibrated and fine-tuned. For a regular filament, you usually won’t need to perform a Flow Rate Calibration. 

Flow Rate Calibration is an advanced process, to be attempted only by those who fully understand its purpose and implications. Incorrect usage can lead to sub-par prints or printer damage. Please make sure to carefully read and understand the process before doing it.

When you need Flow Rate Calibration

Perfecting your prints involves several calibration steps that need to be correctly implemented before considering Flow Calibration. Not all defects in 3D printed objects are the result of inaccurate flow rates. In fact, when using high-quality printers like Bambulab and official Bambu filaments, mechanical tolerances are minimal and the filament standard is extremely high. Therefore, any defects noticed in your prints may result from other calibration aspects that need addressing.

If you notice the following signs in your 3D prints and have already performed other calibrations, such as Flow Dynamics Calibration, but issues persist, then it might be time to consider a Flow Rate Calibration:

1. Over-Extrusion: If you see excess material on your printed object, forming blobs or zits, or the layers seem too thick, it could be a sign of over-extrusion.

2. Under-Extrusion: This is the opposite of over-extrusion. Signs include missing layers, weak infill, or gaps in the print. This could mean that your printer isn’t extruding enough filament.

3. Poor Surface Quality: If the surface of your prints seems rough or uneven, this could be a result of an incorrect flow rate.

4. Weak Structural Integrity: If your prints break easily or don’t seem as sturdy as they should be, this might be due to under-extrusion or poor layer adhesion, which can be improved by flow rate calibration.

Beyond fixing the noted printing defects, Flow Rate Calibration is crucial for foaming materials like LW-PLA used in RC planes(you can refer to Instructions for printing aircraft model with foaming PLA (PLA Aero) | Bambu Lab Wiki). These materials expand greatly when heated, and calibration provides a useful reference flow rate to achieve good printing results with these special filaments.

Is the calibration reliable?

Auto Flow Rate Calibration utilizes Bambu Lab’s Micro-Lidar technology(refer to Automatic Flow Calibration with Bambu Lab Micro Lidar | Bambu Lab Wiki), directly measuring the calibration patterns. However, please be advised that the efficacy and accuracy of this method may be compromised with specific types of materials. Particularly, filaments that are transparent or semi-transparent, sparkling-particles, or have a high-reflective finish may not be suitable for this calibration and can produce less-than-desirable results.

The calibration results may vary between each calibration or filament. We are still improving the accuracy and compatibility of this calibration through firmware updates over time.

Manual calibration criteria can obtain a relatively accurate result, but you need to know the correct calibration method.

Two modes of calibration

Flow Rate calibration has two modes: manual and automatic.

Automatic mode: the user only needs to start the calibration, and the printer will return the calibration results after the printing is finished.

Manual mode: the user needs to judge which parameter to use by observing the quality of the calibration block on the print plate.

Two types of Manual Calibration

The manual mode includes two types: Coarse Calibration and Fine Calibration.

Coarse Calibration is based on the flow ratio value of the filament preset and prints the calibration blocks which the flow values in the range of 80% to 120% based on that value. The step size of coarse calibration is 5%. When you are not sure about the flow ratio of the filament, you can first use coarse calibration to get a better range and then use fine calibration to get a more accurate value.

Fine Calibration is based on a custom flow ratio value and prints the calibration blocks which flow in the range of 91% to 100% based on that value. The step size of fine calibration is 1%. If you already know a reasonable range, and the margin of error is within 10%, you can directly use fine adjustment to get the more accurate value.

How to start a calibration?

Automatic mode

(1) How to start

The printer must be connected before calibration.

(2) Select the material to be calibrated

Select the nozzle diameter of your printer 

(Note: calibration on different nozzle sizes needs support from the printer firmware. For OTA version 01.06.00.00, only 0.4mm nozzle is supported)

Select the plate type of your printer

Synchronize filament list information from ams

Select the filament you want to calibrate, and you can select the filament preset for printing through the filament radio box.

When you have set the required information, you can start the calibration by pressing the “calibration” button.

(3) Calibration printing in progress.

After the printing is finished, you can click the next button to go to the next step.

(4) Save calibration results

After the printing is finished, a flow ratio value that the machine thinks is optimal will be returned. You can save this flow value to a new filament preset. If you modify the name to the same as the original filament preset name used for calibration, you can also overwrite the original filament preset.

Manual mode

(1) How to start

(2) Select the material to be calibrated

Select the calibration type

Complete Calibration: It will first perform a coarse calibration, and then you can perform a fine calibration based on the results of the coarse calibration.

Fine Calibration based on flow ratio: It will directly perform a fine calibration based on the flow ratio you set.

Other steps are the same as the automatic mode.

When you have set the required information, you can start the calibration by pressing the “calibration” button.

(3) Coarse Calibration printing in progress.

After the coarse calibration is finished, you can click the next button to go to the next step.

(4) Save calibration result after Coarse Calibration

By observing the calibration block, select the number corresponding to the calibration block with the smoothest top surface. After selecting, the corresponding flow ratio value will be displayed below. You can continue Fine Calibration based on the currently selected flow ratio value for the next step, or you can skip the next step and save the value to preset directly.

(5) Fine Calibration printing in progress.

(6) Save calibration result after Fine Calibration

By observing the calibration block, select the number corresponding to the calibration block with the smoothest top surface. After selecting, the corresponding flow ratio value will be displayed below. You can save the value to preset.

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