Ever had a print coming out with very visible seams or really unacceptable top surfaces, not to mention impossible to remove supports ???
If so than you probably used Bambu filament with the ID tag or tried to calibrate your custom filament with the Bambu tools…
Who do you trust more > The guy taking a quick look at your basket to charge you or the one who actually counts how many eggs you have in there ? 
The Bambu calibration is a visual one where the user has to know how to judge those 9 patches.
And even then the result can be far off.
Ok, you calibrated the flow ration and the k-factor using Studio but the results won’t impress.
If that’s the case than you are already a step ahead of the rest of users
For some reason many assume that what they get out of the machine can’t look and better…
To fix problems that should not be there they than use ironing to get a better top surface or just start changing the flow ration based on a nickel plated eye sight…
Thankfully there is old farts like me who still remember the old days where literally everything was manual labour …
What do you need?
A good pair of eyes or something like a magnifying glass to help them.
A printer and slicer…
Some callipers and knowing how to use them.
That’s it…
How ?
To have it easy set your flow ratio to 1.0 .
Print the test cube with no infill, not top layers and two walls.
Paint the seam onto a vertical wall, don’t use the corner.
Measure the thickness of the wall.
Assuming you used the 0.2mm standard profile it should be 0.42 for the outer wall and 0.45 for the inner wall.
Any result around the correct 0.87mm mark is acceptable.
Take a look at the seam…
Note whether it is too fat or incomplete looking.
Place this first cube on the left side of your upcoming cube collection
Let’s say your wall measured 0.92mm.
Is that bad? Most likely not as nothing restricted the walls.
But if you measured only 0.85mm at best your flow ratio might be too low.
Hence starting with a flow ration of 1…
We now do some math >
Set Flow ratio divided by the measured wall thickness, then multiplied with the combined set wall thickness.
1 divided by 0.92 = 1,08696 this multiplied by 0.87 gives us 0.94565 - our almost done flow ratio.
0.95 will do fine to continue…
We now established a flow ratio that is great for all prints that only use vertical, two line walls - useless LOL
So we print the cube again after sizing the height down to just 2mm.
Set a honeycomb infill of 15, 2 bottom layers and 5 top layers.
Should leave just enough for a bit on sparse infill…
When done check the top layer very closely…
Our newly established flow ratio was based on two walls with no restriction.
By all means there should be some gaps in your top infill now.
Meaning you have a nice and flat surface but gaps between those infill lines.
If you have too much than the next step is still the same, just instead of slightly increasing the flow ratio you decrease it.
Set this cube aside as well and add some notes for the flow ratio like for the first one.
Increase the flow ratio by, lets say, 0.03 to now 0.98.
Print another 2mm tall cube and compare the top layer to the previous one.
What you want to see is a flat surface with no gaps between the infill lines and no build up where they touch either.
Go up in the flow ratio to close the gap, go down to get rid of build up between the lines.
For translucent filaments it helps to use a black marker pen to paint of the infill lines at a 90 degree angle.
Should only take 3 to 5 cubes to get it right enough.
Ok, flow ratio sorted but how could we improve on the k-factor?
K-factor is what other slicers use as Pressure Advance, which is far better fitting as a name.
Studio offers the line version and the pattern version to calibrate.
For the first you look for the cleanest line, the one that has neither a bulge, nor a thin spot.
For the pattern you pick the corner that is cleanest looking.
The one that is sharp, gap free between the lines and flat on the inside and outside corner.
You might get different results from those tests, so pick the middle value if you do both and they differ.
Now do a test cube again, single wall, no infill, 5 to 10mm high is enough.
Pay attention to the “Seam Gap” in the quality settings !
The seam on the cube wall is what you shall observe now.
Seam gap, k-factor - you lost me…
If that’s what you are thinking right now then let me help you out…
Bambu uses the seam gap to ‘improve’ on the seam.
But many use only the look of the seam to judge the k-factor.
Problem with this approach is that while you get a near perfect seam you often get other problems in other areas where the k-factor plays a role.
You know… sharp corners or where the top infill goes over the walls, fine details…
So you judge the seam you just printed as a reference for the set default ‘Seam Gap’ value in the slicer.
We now move on to printing a complete cube - hurray, or so…
3 bottom layers, 5 top layers, 3 walls, pick your sparse infill and print as tall as you want but 10mm shall do…
This cube is now our reference for the k-factor.
How sharp are those corners, are those layer lines far more dominant on them?
Is the transition from top infill to wall quite rough or even like saw teeth?
Do you a build up in the last corner of the infill?
If all looks good and you are happy with the result then leave the k-factor alone, otherwise give it a slight increase or reduction to compare the results to - pile those cubes up behind the reference cube.
As for the seam (gap) …
A seam poking out of the wall is bad, a gap far worse as it will ruin your prints.
Right now the seam is probably rather visible or maybe show signs of under extrusion.
If the later is the case it means your k-factor is way too high.
All based on the default print profile that is…
If you increase the seam gap the seam gets ‘thinner’ decrease it if you notice a gap or thinning of the seam area.
Don’t be tempted to use the seam gap feature as a correction for a badly calibrated filament…
If you want to check how well it went you can print a cone that you almost flattened.
Use the variable layer height option to slice it with the default 0.2mm profile in 0.08 layers.
Works best if the X and Y dimensions are set to 200% and it results in many fine layers.
If seam gap and k-factor are way off you will get a nasty looking seam…
If it is good enough you will barely see the seam in this worst case example…