3D Printing Garden Cage Hinges

By Michael Gebis, Tue 13 October 2020, in category 3dprinting

My girlfriend's COVID-19 hobby is gardening--broccoli, greens, carrots, radishes, you name it. The only problem has been the rascally neighborhood squirrels and raccoons, who insist on digging in the raised garden beds, ruining her crops. A few weeks ago, with a friend's help, we built PVC cages as protection. PVC construction is probably worth its own blog post someday, but this blog post is about 3d printing.

The remaining problem is that while the cage needs to keep most mammals out, it still needs to let my girlfriend in. As an experiment, we "hinged" one of the cages using metal strap.


However, every time we tilt the cage, there's a TON of stress on the metal straps--one of these days something will break. If the straps break, that's an easy replacement, but I'd rather not have to try to field repair the PVC cage.

So I decided to 3d print some hinges. Back as a freshman in college, I did get some AutoCad experience, but it's been a while. This time, I decided to use OpenSCAD to create the hinge--it has a programmatic interface that meshes better with the way I think than an interactive modeller.

In any case, here's what my "zeroth" attempt looked like--really, this was just an attempt to test my 3d printing pipeline:


The workflow isn't overly complicated, but it's still worth documenting:

The first print showed two issues--the hinge is way, way too tight on the PVC, and the legs were a little too long and weak. So on to the next test print:



Still some issues--the central screw hole is too shallow to hide the screw head. And I still needed to cut the part into two pieces.


Getting better--I changed to using two screw holes, and once they were moved off to the sides, they were deep enough to completely engulf the screw head. As I iterated on my OpenSCAD design, I kept coming up with new terminology. In the code, I started calling the two pieces the "shell" and the "cradle". The remaining problem was that the cradle tabs didn't want to completely fit inside the shell notch. One more iteration, this time chamfering the tabs:


This print was very successful--the parts snapped together like magic, and I'm hoping they will work. But to quote Mike Tyson "Everyone has a plan till they get punched in the mouth." I'll have a chance to try installing these on the weekend.