Update

Designed a 'shelf bumper' that clips on to the risers, no glue or screws required. This allows you to add a 1/4" by up to 1" board to the shelves to protect items from falling off.

I call these my 'because I can' shelves and you'll see why shortly. Covid-19, Earthquakes, Riots, <insert the chaos of 2020>, etc, etc. I think a lot of people found themselves less prepared this year than they either thought they were, or less prepared than they wanted to be. I'm most certainly among them. In an effort to be more prepared, I knew I needed more shelving for storage. My problem was I couldn't find any shelves optimized for the space that I had available. Rather than buy some shelves and have wasted space, I decided to build my own shelves. I went through a few designs and realized while they would do the job, it would be a bear to get them in to the storage room once built AND back out if/when we moved. So I decided they needed to be modular and easy to assemble and disassemble. These shelves are built entirely with PETG brackets (for strength and flexibility), 2x2's, plywood and screws.

There certainly were faster ways to add more shelves, as you can find them just about anywhere. I mentioned I wanted to make the best of the space I had though and that required a custom build.

Material: PETG because I felt PLA was a bit too brittle if the shelves were either shifted by someone or something (i.e. an earthquake).

Infill: 100% for maximum strength (who knows what I'm going to store on them?)

Wall layers:I played around with this one a bit. If you do like 6 or 7 wall layers there is no zig-zag infill on the arms of the bracket. In Cura I found this to be the quickest printing method at around 13 hours per bracket. I was set to do this and then had a change of heart. Inside each bracket is a small 'lip' meant to keep the bracket from just sliding down the riser, essentially fixing it in place atop the 2x2. This lip in essence must be able to hold the brunt of all the weight on the shelf (only the shelf it directly supports). I decided to back off my walls to 4, thus increasing the zig-zag infill in hops of strengthening this lip. At least in my mind it was less likely to shear off with various directions of welded plastic verses everything being stacked and parallel. This bumped the print time to 15.5 hours per bracket.

Supports: They are needed for the lip mentioned above, but they are minimal. Supports 'touching the build plate' will suffice.

Feet: There is a second stl file included which is essentially a 'foot', needed below the bottom shelf. It in essence mimics the support of the 2x2 riser bracing the inner lip AND it keeps the shelves directly off the ground. These were also printed at 100% infill.

Assembly: I chose to have the bracket's flattest side face down on all of the shelves. The main reason I went this route is because it didn't add any additional dimension to the shelve itself. You could invert this if you want more clearance at the bottom, but you will add roughly 1/2 inch to each shelf's depth. There are a lot of screws for assembly. I used eight #6 1-1/4 inch screws per bracket. They add up quick. I then attached plywood to the tops of the shelves using a brad nailer. If I did it again I would be careful not to attach nails directly near the brackets. I did have a couple of nails turn and blow through the PETG. It doesn't look like it caused any structural issues, but I did end up putting that shelf at the top just incase.

Final thoughts: Overall I think the shelves turned out great. They haven't been 'field tested' long to determine a maximum weight, but they feel sturdy enough and handling the brackets themselves before assembly has given me confidence. One night isn't much of a test, but I did leave roughly 120lbs on the first shelf overnight and it was fine. I will note that not all 2x2s are created equal. After designing and printing my first bracket according to standards I found the 2x2s I purchased (luckily only 2) at Lowes were 1/8 inch narrower than a standard 2x2 and they were unusable. In the end I purchased 2x2s from Home Depot. Most of them fit well, but some of them had to be cut down slightly using my tablesaw. Also, due to the variance in width, some of the risers are slightly looser than others which causes a little wobble, but I have no concern of the shelf falling over. Hopefully they prove themselves over time. At approximately 310 hours for the brackets themselves plus whatever it took for the feet, this wasn't a quick project. Assembly took plenty of time as well. This was certainly a 'because I could' project and I had fun seeing it all come together. Hopefully someone else finds them useful.