Flow Rate Calibration confusing results

Bambu Lab X1 Series Bambu Lab X1C
1

Cube-Method

Yesterday I printed a hollow Cube.

All Line Widths were set to 0,40mm, 2 Wall Loops, no Top Shell Layer, 4 Bottom Layers, 0% infill.

Calibration-Box-1024
Calibration-Box-10241024×768 307 KB

Flow-Rate-Calibration-Quality-Settings
Flow-Rate-Calibration-Quality-Settings425×950 145 KB

Flow-Rate-Calibration-Strength-Settings
Flow-Rate-Calibration-Strength-Settings422×975 162 KB

Test-Cube
Test-Cube1020×791 122 KB

Then I measured the real Wall thickness of the 4 Side-Walls and calculated the Flow Rate like recommended here:

https://www.printables.com/de/model/81314-flow-calibration-cube

After this I multiplied the old with the new calculated flow multiplier.

I repeated this process until my walls had a thickness of exactly 0,8 mm.

My „Bambu PETG Basic@BBL X1C Copy“ Flow Ratio is now 1,07.

Today I ran the LIDAR-assisted Auto Calibration test at Bambu Studio.

Auto-Calibration-Test-1024
Auto-Calibration-Test-10241024×935 377 KB

After the Test the filament “Bambu PETG Basic Flow Rate Calibrated_A1” was created.

The flow ratio there is 0.97.

Then I printed another cube with this new Filament-Setting.

I previously deselected the “Automatic flow calibration using Micro Lidar”.

As I guessed, the outer Walls of the Cube does not fit anymore.

Wall-Thickness-1024
Wall-Thickness-10241024×768 219 KB

Then I printed another Cube of the same calibrated Material, but with the Checkbox “Automatic flow calibration using Micro Lidar” on.

RESULT:

Both Cubes have wall thicknesses around 0,74mm.

The automatically generated flow ratio of 0.97 does not seem to fit.

Can someone help me to think clearly about this?

L.G.

Frank

2

This is due to how Slic3r based Slicers including Bambu Studio and Orca Slicer assume the shape of the extruded lines, as well as compensate for the gap between the assumed shapes by overlapping the extrusion lines.

Without any feature such as the experimental “precise wall” functionality in Orca Slicer, two 0.4mm walls at 0.2mm layer height never equal 0.8mm but actually 0.757mm (according to Andrew Ellis) or 0.714mm (according to SoftFever), as lines are put next to each other with an overlap. Otherwise you’d have a gap in between the lines, due to the round edges of the line.

Andrew Ellis has a great explanation of this in his Tuning Guide:

And there’s a great explanation of the Precise Wall feature by SoftFever, as well:

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3

Hi, du hast Wandstärken von 0,4mm und eine Überlappung von 15% eingestellt. Das heißt, deine innere Wand überlappt zu 15% in die äußere Wand.
Ziehe 15% von der inneren Wandstärke von 0,4mm ab, macht 0,34mm. Zusammen mit der äußeren Wand kommst du also auch eine Gesamtstärke von 0,34mm + 0,4mm = 0,74mm.
Ist doch alles korrekt.

Gruß
Rene

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