Thank you for this writeup, this is great and exactly what I was looking for. Helping a friend automate the door on his coop.
I have a question on some of the parts you used. You didn't list the stepper motor you used but I could see 17HS8401 written on it so I'm assuming it's a Nema17 17HS8401? Do you have the exact one you used? I'd love to make sure the mounting points match up.
Also I'm unclear on the rod you mention, you said 13cm diameter 8 steel rod in the readme, but I see a threaded rod in there. Do you have any more info on what you used?