Summary

Simple 3D printed hangers for suspending 15mm rod beneath wire shelving.

Instructions

After looking all over Thingiverse for something already created for wire shelving suspension, I was dismayed how many ridiculously over-engineered devices had been contrived for such a simple problem. My PowerSpec 3DX sits on the third shelf of an 18"Dx48"Wx76"H 5-shelf wire shelving unit with wheels. It was obvious the wire shelves would easily allow a hanger device to be suspended below the printer to store a large number of filament reels. The volume available also lends itself to building an enclosed box that I can "ovenize" to keep the filament dry... that is a future project, so stay tuned!
I have learned that cheap and effective solutions often involve good MacGuyver skills and a trip to the local dollar store -- Dollar Tree had just what I was looking for! I needed a sturdy rod to hang a row of filament reels on, and while yes, I could look into storage solutions at Home Depot or Lowes - closet rods, curtain rods, dowels, threaded rod, etc... I knew those would cost much more. PVC would be cheap, but too large in diameter for my specialty reels and rather flimsy. I suppose if you had a lot of spare pipe-hanging strap you could make it work, but...
My journey to Dollar Tree yielded a $1 Swiffer-clone with a slender metal handle about 3ft long and I would find, 15mm diameter. A quick re-acquaintance with SketchUp and some quick measurements I gathered - 3.8mm shelving wire, 15mm shaft, reel diameter around 8" for large reels, I came up with this creation. I carefully considered the layer-splitting delamination potential when choosing how to orient this to the print bed. Be sure to print so the hook is laying on its side - you don't want Z-axis laminated layers supporting a load.
I used MakerWare to place 4 copies on the bed then created an X3G file on an SD card for printing. Render settings were 2 shells, 50% infill, 0.1mm layer height, 230C extruder + 110C heated bed, ABS filament. Extrude speed 90mm/s, travel 150mm/s. The layer height makes for slow printing but the detail is great and less likely to delaminate.
After a 13-hour build, I was very pleased with the results. The rod hole was designed to 15.1mm and needed some filing and sanding to smooth it and slightly enlarge it. You might want to enlarge to 15.2 or larger to minimize the need to sand it, but I preferred the very tight fit so the rod won't come loose in use. The hook end did not need trimming to fit.
I found the cheap 15mm rod would hold about 8kg over an 18" span without sagging excessively. While it would work out to 36" there was more than an inch of deflection. For the full length, I'd recommend a total of 3 hangers. I built 2 sets using 2 handle rods and 4 hangers. I have room to expand another 18" by printing another couple of hangers. I put ABS reels on one rod and PLA on another. Also, the specialty small reel of FilaFlex which really constrains the rod size to about 15mm. Looks like a great solution with the inch-wide hanger being much stronger than the 15mm rod.

Filament Reel Hangers for 15mm Rod