Main heart printed with 20% infill, all other parts printed with 100%
I used PLA for this, but I will be making another one in transparent red PETG so that the whole heart will light up.
Superglue the bevel gears together in the orientation you want. I have included a cut-away file so you easily see how I assembled it. I bonded the 2 bone sections to the heart, then painted everything, before I glued all the gears/window to the heart. I gave it a light coating of white Krylon fusion paint as a primer, and acrylic brushed on the color.
I added solid copper wire (scrap house wiring), brass screws, knurled nuts (home depot) and some leather to give it some more realism. You will need to figure out where you want the wires to go and drill your own holes. The barbed wire section is just copper wire with a couple loops to look like barbs, and then I tightly wrapped another piece of wire around it.
I also used a piece of clear plastic (piece of old welding mask shield) bonded to the back of the window frame before I glued the whole window section to the heart. Make sure the inside of the lense is clean before you permanently glue it on.
Semi after the fact, I decided to add an LED tea light to the heart so there is light behind the gear section. This isn't included in the files, since most LED lights/switches will be different. I simply removed most of the tea light casing, and took a hole saw to the back flat section of the heart. I had to pry out some of the infill to make room for the tea light. I then made a cover which screws to the flat section of the heart, and holds the battery in tight. I bonded nuts flush to the flat surface with superglue. The notch in the cover is to access the on/off switch. I have included this cover, but it may not work with your LED light.
LED Tea Light effect. (Sound effects added post production)