Pressure Advance Calibration
This is a beginner's guide for calibrating the pressure advance. I'm gonna guide you step by step through the process and I'm gonna show you some tricks that will help you find more easily the right settings.
I suggest reading the complete guide before you start. Why...? There is a lot of information, the information is not always in order to keep the guide clear.
For you to complete this guide in success I assume that your 3D printer is already printing a good product and you want to fine tune the printer for a better printing result.
The next conditions should be considered before following the guide:
I suggest to use Simplify3D with this guide because I can’t promise that any other slicer would slice the object the right way that is needed for this guide. The following settings must be used during this guide, using any other values for this test would undermine the conclusion that follows out of the test.
Slicer Settings
Nozzle diameter: 0.40mm
Extrusion Multiplier: use your own value
Extrusion width: 0.48 mm
Primary Layer Height: 0.2mm
First Layer Height: 100%
Internal Fill Pattern: Rectilinear
Infill Percentage: 100%
Infill Extrusion Width: 100%
Outline Overlap: from 10% to 30% should be fine
First step:
I recommend you start with the PA Cube, it is a square cube by 20x20x20 what you can easily make bigger in Simplify3D with the setting ''Change Scaling''. You need to make the test cube 50x50x50 for this test.
In Simplify3D you need a zero top and bottom layer, you need 2 Outline/perimeter shells with zero infill and I suggest a printing height of 20mm. With Skirt/Brim you need an offset of zero and 10 brims for the first layer. You can still make some small adjustments for the first layer height and the brim is wide enough for this test to have absolutely no issues with warping. The beginning and the end of the retracting needs to be aligned to a single point, in Simplify3D this is called the start points. And Ooze Control Behavior needs no check mark. Now you can slice the test cube to a g-code and it's ready for printing. 
Second step:
Go to your DWC (duet web controler) and load the program. Wait till the printer start printing and make sure everything goes fine. You have enought time to watch the complete first layer to finish before you have to do the next step.
So now use the G-code console and type the following code:
M572 D0 S0.2
To make sure that the Pressure Advance is activated you can check the PA by typing the code M572 and you should get a replay stating the amount of pressure advance.
This will only work when you have a Bondtech Extruder mounted!
The next part is maybe confusing but you will get it threw the process, you gonna rise the Pressure Advance with 0.1 (so from S0.2, you take the next step to S0.3, then S0.4.... S0.5 and so forth). There is going to be a change in sound from the bondtech extruder, this sound is going to be an recognizable raw extruder sound and you would think there is something wrong. You stop rising the pressure advance when you recognize the sound and you can let the 3D printer finish it's print.
See video
Second video
We have now determined the maximum Pressure Advance value. And we can continue to step 3.
Step 3:
Load the PA Infill Test.3MF in Simplify3D.
Now change the following in Simplify3D. You need 1 top and 1 bottomlayer, you need 2 Outline/perimeter shells with 100% infill (reticular) and I suggest turning off the printing height of 20mm. With Skirt/Brim you need an offset off 1mm and 6 brims for the first layer.
Turn off the pressure advance with ''M572 D0 S0''. Then you can start the program you just sliced (PA infill test.3FM). Make sure the first layer is good, there is enough time for that. If the first layer is printed and there is a resume off the following layers you can turn on the PA with ‘’M572 D0 S0.2’’. Now you go back to the 3D object being printed and you look at the infill, with the wrong Pressure Advance the infill is going to look bad.
If pressure advance is to low?
The infill would be over extruding. The perimeters would be thin, but keep in mind that the nozzle pressure is too high and it needs time to stabilize
If pressure advance is too high?
The infill would be under extruding, the perimeters will be too thick but at the start of the print there could be a under extrusion because the filament is pulled back to much with the bad Pressure Advance value. 
Extra info: With a low- or high-Pressure Advance the nozzle pressure will recover if the Pressure Advance is not being enabled for a certain kind of period while printing. Think about the outside perimeter where you would go around the object without any interruption. In this situation the extrusion could be bad at the beginning but it would recover around halfway the perimeter. But this also depends on how far away you are with finding the right pressure advance.
So, from this point it’s for you to find the right Pressure Advance and if you manage to find the right value then you completed the first few steps.
The result should look likes this.
Step 4 (Final calibration):
With the last settings you used in Simplify3D for the PA infill test.3FM you can slice the next part.
PA Infill Test (Expert).3MF
Use the Pressure Advanced you got from step 3 and see the results. If it goes well then there is no need for adjustments of the Pressure Advance value. If you are not satisfied with the result you can try a different Pressure Advance value.
Step 5:
So, if everything is done correctly we have a the right Pressure Advance value what we can use for printing a product. For this test I suggest printing the PA Box.3MF.
After layer 8, (@printing height 1.5mm) the infill will be separated into 2 infills. From this point we have to keep looking at the part being printed and see how the gap infill goes with the Pressure Advance.
Extra Info: Because of the radius inside the box there are going to be a few weird gap infills. Let call these gap infills ‘’exotic gaps’', and with the right Pressure Advance value the printer would fill all these gaps without any problems.
After layer 20 (@Z height of 3.90mm) you can leave the part to finish printing. We have to wait till the print is finished and then we can continue the last process in step 5 were we start measuring the object.
