PSA: START HERE! Calibration made SIMPLE & please SHARE User Tips!

I am a new Bambu 3D printer here

Agree that this doesn’t seem logic.
Just used the calculation examples for each step
During testing the numbers and affect appear to be logic.

I noticed that you dont have the retraction calibration in your version of orca slicer?


I would like to ask some specific questions about the calibration test “Flow Rate” in Orca Slicer.

I understand the idea behind the Pass 1 test. Each tile is printed with a different value for the flow ratio. After this test, you pick the tile, that looks and feels the best and insert the number into the equation. Then, you save this value to the material flow ratio. Lets say this new value is 1,29.

Here comes the confusing part for me:
In Pass 2, you start from 0 = flow ratio of 1 and go downwards to -9 = flow ratio of XYZ.

What about the newly saved flow ration of 1,29? Shouldnt this be the 0 value? 0 = 1,29 and from there on go downwards? Is this newly saved flow ration ignored in Pass 2? I dont get it…

Can someone enlighten me please, where my mistake is? Thanks!

I think this is where you are going astray. The “Zero” sample in both passes uses the value currently saved in the filament preset. So say you changed the original value of 1 to 1.029, and then saved it. The second pass will print the “Zero” sample using 1.029.

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Hello, thanks for your reply!

Do I have a wrong understand of these values here?

Shouldnt Pass 1 and tile 0 be my material flow ratio value of 0.98?
And from there on go upwards and downwards?

In Pass 2, shouldnt tile 0 be my newly saved material flow ratio of XYZ and from there go downwards?

I dont know, if I over complicate this test by thinking too much…

It’s early here, I have not had my coffee yet, and I can’t find the explanation of how the test works that led to my current understanding, but it obviously does work because the samples all print differently…

This is how I think it works. (Somebody correct me if I’m wrong!)

The saved filament preset determines the default flow ratio for the print overall.

The flow ratio settings in “Walls and Surfaces” then modify the default flow ratio for specific parts of the print. The default is multiplied by the number entered here. You can set a different flow ratio on the walls than the top or the bottom, by entering a number bigger or smaller than 1. In Per Object mode you can also modify the default fault ratio for only one out of several items,

Slice the Pass 2 calibration test again, and look at the Per Object flow ratios for each sample:

So with a filament preset of 0.98, the sample marked -5 would have a flow ratio of 0.98 * 0.95 = 0.931

I think.

Time for :coffee:

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Hello Ikraus,

thanks for your reply. In the meantime, I was able to figure it out on my own.

The error was in my way of mixing up absolute numbers with percentage numbers.

On the Github Flow Rate Calibration page, I saw a GIF-video and there, the object related flow rate was in %. In my OrcaSlicer version, I dont have the %-unit in the object related flow rate field. This led me to think, that it is an absolute number and that this value is the “driver” for the test.

Now I know, that the filament flow rate value is the “driver” for this test and the object related flow rate values are the percentages, that refer to the filament flow rate value.

Well, …add one coffee for me too, please :smiley:

Can we start a shared spreadsheet of filament types and shrinkage factors?

This doesn’t seem feasable unless anyone using it sets their room to a standard temperature, like a 20°C guideline, because plastic shrinks alot in relation to temperature as well as other factors. The reliable way is to print the sample yourself to test your machine in your specific environnement.

It’s going to be tied to temperature difference, so room temp give or take a few degrees won’t have any significant impact on the result.

I must seem to be missing something here. The calibration tests in the Orca do not let you change layer height. For example: The max volumetric speed test when using .8mm tip is .64 and if you try to change it it will just mess up the output code. Obviously these tests are custom gcode to be able to print a part with different flow rates at different layers.
A layer height of .64 with .8tip will obviously produce a much higher value that say .24 layer height with same tip. What am i missing?

The test is a measure of how much volume can be melted and extruded in a period of time. Whatever the layer height, the test keeps increasing the print speed until you see signs of underextrusion. A thicker layer would just fail at a slower speed than a thin one, the maximum flow rate will be the same.

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Sorry, but I think you are incorrect. If you test a .8mm tip for tpu it default sets layer height at .64 which will flow to about 35mm cubed/s. If you run the same tip at a .24mm height you are choking the flow to the same effect as a smaller orifice.
The test needs to be able to run the tip at the layer height you are actually going to print at.
If you try to override the settings it messes up the output of the custom Gcode.
If I am completely wrong and someone sets me straight I will happily admit and learn and move on. But this seems pretty straight forward and exactly what all my testing has proven.
My ears are open. Thanks

With a nozzle diameter and layer height, how are you getting a flow rate of 35³/s without a speed? That’s all the max volumetric speed is doing is determining a max print speed based on how much melted plastic the printer can supply.

How is the smaller layer height choking the flow and acting like a smaller nozzle size? The smaller height should allow a max speed of around 2.5x of the taller layer max, but basically equal volumetric speed. And assuming there isn’t another print speed setting preventing it.

I’m also not sure what you’re looking at in the G code but the line width and height shouldn’t matter that it’s different than what you print at since it’s finding the max volumetric rate. The height and width are basically making a rectangle (mm²) that combined with the speed (mm/s) give a volumetric rate (mm³/s). If you change the rectangle, height and width, it will change the max speed.

The volumetric flow rate depends on the material, temperature, the power that can be supplied to the hot end, the nozzle size it’s squeezing thru and probably a handful of others before it gets out the nozzle, that control how much melted plastic can be supplied per second before it can’t keep up. But the height and width shouldn’t effect much as it’s just the shape the plastic ends up in and once it gets thru the nozzle the resistance drops off and shouldn’t effect the flow except maybe at very small layer heights.