This simplest calibration model allows you to calibrate the filament purge in the range of 0-200mm 3 and 0-400 mm 3, I made it after the release of the bambu studio 1.9.0 Public Beta update, as they added the functionality of a long retraction before changing the filament.

1. Create new project in Bambu-Studio
2. Add retract before filament change (like here: https://github.com/bambulab/BambuStudio/releases/tag/v01.09.00.60)
3. Load this calibration model 
4. Set flushing volumes to 10 (on screen from 1 to 4, from 2 to 1…)
   
5. Select model colors, outer model is “from” color, inner is “to” color. And don't forget to change the order of printing the colors of the first layer (by clicking on the gear near buildplate in bambu studio), outer color must be printed first.
   
6. Slice model, then print.
7. Every mark means +20mm3 to flush volume, choose better result, in my case it is around 50mm3, add 10mm3 from step 4, and set this value (60mm3) in bambu slicer flush volume.
   
8. If 200mm3 is not enough for u, use 400mm3 model.

Thanks!