Each segment is its own solid. A knob on the rear segment sits in a ring on the front one, with the air gap all round and 45Β° lips above and below, so it turns side to side but cannot lift or pull out. Every surface is vertical or at least 45Β°, and every body sits flat on the bed.
Links have fixed minimums on every design: a neck at least 3 mm wide (7 lines at 0.42 mm), a 2.6 mm socket wall, 0.9 mm lips, and a socket mouth at least 0.7 mm narrower than the knob.
Hinged wings and flippers use a horizontal hinge: two body knuckles with 45Β° cone pins hold the part's knuckle between them.
The accessory port is a blind hole with a 45Β° undercut. Add-ons print flat with a split peg pointing up; flip one over and push it in. The barb is wider than the mouth by the snap (0.3β0.5 mm, less on looser printers), clicks into the undercut and lets the add-on swivel. The fit gap is your printer's air gap.
The 3MF places the pet on your plate clear of keep-out zones and the prime tower, and switches brim and supports off for it. Pick your printer, filament and a 0.2 mm profile in the slicer, and print the first layer slowly.