This is my mini Ballista, everything printed in place.
Fires the arrow without problem through the room and further!
I used four layers of cotton sewing thread as bowstring.
Easiest loading method is with help of the arrow as seen in the video.
Tested with PETG and PLA both with 90% infill and layer height of 0,2mm.
Printtime with this settings is about 2 hours.
Print and test video: https://youtu.be/olYlUPdZJGM
Have fun!