The making of NO DOG

Warning to you geocachers out there. This post contains major SPOILERS for a geocache in North Olmsted, Ohio. If you don't want to ruin the surprise, go and find NO DOG first. It's okay, we'll wait.

For those of you who don't know what geocaching is, it's a treasure hunting game using GPS devices. If you live anywhere near a medium-sized or larger town, there are probably a few geocaches nearby. One person hides a geocache and publishes the GPS coordinates on the web. Then other geocachers use those coordinates to find the cache. The cache contains a log book and possibly inexpensive trinkets to trade. The folks in the geocaching community work very hard to be sure that geocaching is a safe, non-destructive, family-friendly way to get outdoors and have fun. To learn more about this sport, go to Geocaching.com, the largest geocaching website and read all about it.

Anyway, I just recently placed a cache that I'm rather proud of. The idea was to create a geocache that was completely visible, yet blends into the environment so well that most people would not pay any attention to it at all. So I decided to create a valve cover. Originally, I was thinking of something like this, maybe embedded into a sidewalk:



I played with the idea of casting the cover out of metal, but I don't have any of the equipment to do that, plus making the mold for something like that would be a long process, and then I'd have to find someone pouring a sidewalk who was willing to let me include it in their pour. So in the end, I decided to go with a cover more like the kind used for sprinkler systems. That being plastic, I could 3-D print it. My cover needed to connect to some sort of box, so I chose the DURA Model 60 6-inch round valve box.

 

 I wanted to go with something official-sounding on the cover. Official-sounding and yet clearly not a real government organization, so I went with "North Olmsted Department of Geocaching", partly because it shortens nicely to NO DOG, which makes a great cache name. I started by designing the cover using Trimble Sketchup. Sketchup allows you to build a model of a 3D solid quickly, and best of all, there's a free version! Sketchup also allows for extensions, including one that will output an STL file, which is the standard format for 3D printing. My cover looked like this in Sketchup:

Next, I needed to turn the STL file into instructions specific to the 3D printer I was going to use to make my part. I knew that the printer I was going to use was a MakerBot Replicator 2 (more on that in a moment), so I used MakerWare to slice the geometry into the thin layers that the printer lays down. I had originally planned on making a complete replacement for the cover that came with the box. But as I worked on it, I began to realize that the 3D printer would not be happy with all the overhanging surfaces, so eventually I hit upon the idea of a new top surface glued onto the existing cover. Shown here is the toolpath of my cover at layer 66, about three-quarters of the way through the print. Note how the program fills in the interior of the part with a honeycomb pattern to reduce the amount of plastic used.

Unfortunately, I don't have a 3D printer. But I live in the greater Cleveland area, and the Cleveland Public Library has a makerspace called "Tech Central".  I have to give a big shout-out to these folks, because not only do they give the public access to 3D printers, a laser cutter, video equipment, computers and so and more for the cost of a library card (i.e. free), but the Tech Central folks are very helpful for people getting started.  This is one example of how libraries can stay relevant in the digital age.  I submitted my print job by e-mail and a few days later I got a reply that my part was printed.  They charge the cost of the plastic, which was a few bucks for a 6" disk.

Once I had the cache outer container, I needed a place to put it.  I asked the administrative board at North Olmsted United Methodist Church and they not only agreed, but pointed out a natural hole in their front lawn where a tree had been.

Note: I'm going to add a picture of the finished product, in place, just as soon as I take one.