Low Cost Cable Management Arms - Multiple Configurations

The Problem

I am building an updated print garden loosely based on an enclosed server rack design, complete with printers on drawers, draw through air, and cable management.  To keep things tidy, I wanted to use similar style server cable management arms on the back of the printer drawers, but holy cow are they expensive... with prices starting at $100 USD for even the amazon knockoffs (in simplest terms, it's a hinge on a stick!), and I still would not be able to use them in the orientation I wanted... So, off to the yellow pad CAD I went, eventually settling on a design I was happy with.  Vertically oriented folding arms, with a channel for cables to be secured, and hinges designed for mounting to 2020 or 3030 hardware using minimal hardware.

So... we have the following for design constraints:

• Lowest cost possible by minimizing hardware needed to what is on hand (10mm rods, m3x14 bolts, T-Nuts for each of the extrusion types, and m3nS nuts).

• Printable with no supports

• Rigid in all axes except one

• Smallest footprint possible when folded, but able to reach at least 60cm when drawer fully opened

• Cable arm to install vertically, rather than horizontally

Dumpster Diving

Now on a mission to see just how inexpensive I could make one of these, I started the thrift store / garage sale / scratch-and-dent aisle hunt for some simple hardware... rods or flats would work well for structure to bridge the gap between the 3D printed parts.  I laned on some 10mm hollow steel rods courtesy of an old clothes drying rack.  I cut them in half and wound up with rods of about 300mm (12") in length as the base for the arms.  I also had a bunch of m3x14mm fasteners and m3nS (square) nuts laying around from some other projects... so I would be designing to use up what supply I had left.

Iterative Design

Starting with my simple sketches, off to Shapr3D I went to model up a basic 3D printed scissor-style hinge as Design Iteration 1, including a clamping mechanism for 2 of the 10mm rods for each of the straight lengths of the arm.  This included a 2 part pivot, and a 2 part mechanism on each end.  This turned out fine, and worked well enough, but had the downside of potentially pinching either the cable, or a finger.  This also had the possibility of hyper-extending the joint and causing the whole thing to crash or break.  So, back to the drawing board.  I have included this model as it may be useful for other builders.  It includes several different pivot styles allowing for the use of square nuts, hex nuts, or just straight threading into the plastic.  Honestly, this would be good for something like a microphone, light or camera arm pivot.

Design Iteration 2 flattened the model and added a 'lock' of sorts, to prevent the hinge from hyper-extending.  I placed the lockout in a way to allow up to 165 degrees of 'open' on the arm, so that it would never lock up, or hyper extend.  The orientation of the arm pieces also changed.  This was to allow a full length drawer to be used and for the cable management arm to be completely folded when in stowed mode.  At this point, I also worked up the ends of the arm to allow for mounting on either 2020 or 3030 aluminum extrusion.  The end joints are design to be assembled in place, and I have included a version that uses a 2 part pivot as well as one that uses a single part pivot threading directly into the pivot on the other side.

Design Iteration 3 focused on improving the 'elbow' joint a bit.  Mainly, I wanted a smooth surface with no lumps, bumps or moving bits to potentially cause a pinch in any cables I were to run along the joint.  This resulted in a concealed version of the hyper-extension lock.  I also cleaned up the profiles where the ends connect to the aluminum extrusion to fit more snugly.  Finally I reached a point where I was happy enough with the design to call it 'done'.  Final dimensions are 32mm x 45mm x Whatever length rods you use.

Print Settings

Print the STLs as shown.  They are already in the optimal orientation and should not require supports, at all.  I printed the main hinge bodies in PLA, and the pivot in PETG, but any material would be fine.  .2 layer, 3 perimeter, cubic infill, and Hilbert curve top and bottom.

Materials

• PLA or PETG

• Some repurposed 10mm tubes/rods, cut to desired length.  I used rods I cut down from an old drying rack like this one.  This is WAAAY less expensive than buying rods or tubes on their own.

• m3x14 socket head bolts

• m3nS Square Nuts

• 3030 T-Nuts

• 2020 T-Nuts

Assembly

Assembly is pretty straight forward. Each end of a joint is a mirror of it's other half.  Depending on your printer's tolerances, you may need to chase the holes with a drill bit to clean them up.  But I have included chamfers along all sides to compensate to elephant footing, and the like, so you should be good.

On each end piece, insert an m3nS into the corresponding slot Add the clamp top, and tighten down the clamp using an m3x14 hex head bolt.  Assemble by flipping one over the other and then connecting the two pivot pieces.

For the ends of the arm, start by attaching the end to the extrusion using an m5 or m6 t-nut.  Next attach the end of the arm using either 1 or 2 part pivot.  

To attach to the extrusion use standard T-Nuts sized for each.  An alternative is to print some T-Nuts and use inserted captive nuts (like these: 

Conclusion

Overall I am happy with everything about this little design effort.  One area I will likely revisit will be how this attaches to the frame and the drawer slide.  I was really trying to minimize overall footprint, but that just added complexity to the installation process. So, putting an ear on the one side so that the attach point is not concealed seemed a good upgrade so, I have included a set of those, as well.

For the offset anchors, I have also included a set to allow you to compensate for the step between 2020 and 3030 when installing along the same centerline.    

And vua-la.  A very cost effective means of cable management within an enclosure.

Enjoy!