Flow Ratio Calibration Cube 20x20x20

This is a simple calibration cube to help determine the correct flow ratio. It is an exactly 20mm cubed solid shape. Everything below is based on a Bambu Lab P1P with a 0.4mm nozzle, but I would assume you can scale up/down to 0.2mm/0.6mm nozzles. This has been done using the Bambu Lab Studio, which is a fork of the PrusaSlicer so hopefully it will work in there. 

To perform the calibration, you must have either a micrometre or callipers (digital are easier to use) that are accurate to 0.01mm. If you are serious about 3D printing and making strong, consistent and accurate prints then a pair of digital callipers are a worthwhile investment.

You are going to be printing the cube in "vase mode" with a single wall thickness of 0.45mm, so we are going to have to change some of the slicer settings. 

• Open the slicer, go to the Quality settings and make sure that the wall line widths are all set to 0.45mm (photo #2)
• In the Strength settings change the Wall loops to 1, Top  shell layers to 0 and Sparse infill density to 0  (photo #3)

Go ahead and print this out. You should end up with a 20mm square, open top box with thin sides (photo #1).

Now you need to measure the thickness of the 4 walls (photo #4) and average them out. Don't go too close to the corners as there might be bulging there and don't squeeze the callipers too tight as this will deform the plastic and give a false reading.

It's worth pointing out that unless your callipers have a valid calibration certificate, then they are probably not 100% accurate. If you are reading 0.44/0.46mm then your flow rate is about right and you might want to stop here.

We can now calculate our new flow ratio. To do this we need the current flow ratio, which you can find in the filament settings (photo #5) and the wall thickness that we measured previously

New Flow Ratio = (Expected Wall Thickness/Measure Wall Thickness) x Current Flow Ratio

For this example it would be (0.45/0.44) x 0.96 = 0.98

You would replace the current flow ratio in the filament settings with 0.98

Hopefully that will be all you need to do. You can reprint the cube if you like and check to see if the wall thickness has change to 0.45 (or close to). If you get a stupid flow ratio value, then maybe stop and take a look at what you did in case there is an error somewhere. The value should lie somewhere between 0.90 and 1.10 for most common materials. I've got some TPU that likes 0.90 and some PETG that likes 0.98 and nothing else outside those values.

Good luck and let me know how you get on!