I did this design upon a request. It is a remix of Tiger Ace’s, from his German heavy AA package.
I took the basic model 18/36 Flak Gun.
After resizing the model, I reinforced for the barrel, gun shield, and deployed base. I filled the open spaces within the model, as these do not translate well in a print.
I separated the barrel and the gun mount.
I separated the four pads on the bottom of the gun base, so it prints flat to the build plate, and the pads fit in small recesses at the end of the four trail arms.
I also separated the small half moon shaped trunnion that is under the gun breech. It is attached, post print, in a small recess on the underside of the barrel.
Please note that printing any field gun is quite different from printing an AFV. There are a lot of gaps and angles and the like, so PLEASE be very careful removing the support material (and please no NOT try to print without supports!). Look at the .stl on your CAD program to see what should be there, and remove what shouldn’t. It seems obvious, but it is difficult, post print, to be sure what is to be cut off and what is to stay.
When you are ready to assemble, ensure all the support material is off. the barrel is a very tight fit, enters from the rear of the shield, and the protrusion in the gun mount fits a recess on the bottom of the barrel. the filament will flex to allow this fit.