Repairs You Can Print: Better Cable Splicing With 3D Printed Parts

A while back, [Marius] was faced with a problem. A friend of his lives in the middle of a rainforest, and a microphone was attacked by a dirty, greasy rat. The cable was gnawed in half, and with it went a vital means of communication with the outside world. The usual way of fixing a five- or six-conductor cable is with heat shrink, lineman’s splices, insulating tape, and luck. [Marius] needed something better than that, so he turned to his 3D printer and crafted his own wire splice enclosure.

The microphone in question is a fancy Jenal jobbie with a half-dozen or so conductors in the cable. A junction box was the obvious solution to this problem, and a few prototypes, ranging from rectangular to fancy oval boxes embossed with a logo were spat out on a 3D printer. These junction boxes have holes on either end, and when the cable ends are threaded through these holes, the wires can be spliced, soldered, and insulated from each other.

This microphone had to hold up to the rigors of the rainforest and rats, so [Marius] had to include some provisions for waterproofing. This came in the form of a hot glue gun; just fill the junction box with melted hot glue, pop the cover on, and just wait for it to cool. Like all good repairs, it works, and by the time this repair finally gives out, something else in the microphone is sure to go bad.

It’s a great repair, and an excellent example of how a 3D printer can make repairs easy, simple, cheap, and almost as good as the stock part. You can check out a few videos of the repair below.

20 thoughts on “Repairs You Can Print: Better Cable Splicing With 3D Printed Parts

  1. Graet fix, if that is what must be done. Otherwise for these coiled types, a new one has no bobble in the middle to catch on things. It it was encased in a foot of 1″ pvc pipe, it would retract into the pipe, protected when at rest, but not annoy much in use. I can see a hot glue gun and mini-printer in the forest are a new must. ;>) Just hot glue would have done the job in a pinch, w solder and an iron or heated nail. We ARE roughing it, are we not??? But still, a sano appearance. Good job. Maybe a male-female plug ‘n socket connector?

  2. He could’ve used any sort of open ended plastic cylinder and filled it with hot glue just as easily. Same result and probably less complicated than attempting to run a 3d printer in a forest….. “smh”…

    1. This isn’t necessarily true. A properly dialed in printer with correct slicer settings will yield a watertight print. I made a replacement laundry detergent holding tray for my washer because the design of the original was terrible. It was printed in white pla three years ago on an old printrbot and its still holding up fine. After a wash cycle completes some water usually is trapped in the tray and after a few days it should have all leaked out but the exterior of the tray is always bone dry. While I think this wire splice repair was excessive, I believe it has proven that a printer can certainly be useful even when more economical options exist. I mean, if you have the tools why not use them?

  3. I see a common thread in most of these articles – iterations of prints.
    Forgive my lack of 3D printing experience, but doesn’t that drive up the time (CAD and printing) and cost of filament considerably?

    Generally when fixing things without 3D printing, I don’t take several attempts to do it, I just do it.

    1. Filament is generally cheap, and time is a trade off; if you need the part yesterday, you don’t have time to iterate, but if you have other things to work on you can be productive while a few versions print. Sometimes you iterate in order to test the limits of your printer, other times I’ve just been lazy and didn’t want to ‘measure twice, cut once’. And sometimes holding the part informs you of how else you could have designed it, which you could argue is a skill you should get better at over time, but everyone starts somewhere.

      And sometimes I’ve made a good part but afterwards I see how I could have improved it. Since my time required to tweak the CAD and hit Print is very minimal, I might as well pop out an iteration and use it.

    1. Wrap the splice in copper foil tape, spray the part with conductive paint, use conductive filament.

      Or do nothing. Really, 99% of the projects here don’t take EMI into account, some of which are much worse offenders than a little exposed audio wiring.

  4. Since PLA is made from biodegradable materials like corn starch or cane sugar, doesn’t this risk inviting the rats back for another round of “wreck the cable”? Would wrapping the joint in steel wool before stuffing it in the blob provide a deterrent layer?

    1. Corn is first processed into starch, and then hydrolysis of the starch (acid or enzymatic) yields glucose, just like ordinary glucose “corn syrup” production. Sugar cane or other similar feedstocks may also be used, with sucrose first hydrolyzed into glucose and fructose depending on what’s optimal for the particular bacterial strain used.

      Glucose is metabolized by appropriate bacteria in a bioreactor under the right conditions, yielding L-lactic acid. Lactic acid can be synthesized from acetaldehyde, but biological synthesis is easier and is becoming widespread.

      L-lactic acid is purified and heated, driving off the water to form an oligomer with ~10 units. This can then be “cracked” in the presence of a tin catalyst to yield L,L-lactide which is removed by distillation and purified. L,L-lactide is then polymerized with a tin catalyst to high molecular weight poly(L-lactic acid).

      PLA is commonly made from corn, yes, but it’s not like making a cake. It’s still an insoluble high-molecular-weight organic polymer, not particularly tasty.

  5. Roughing it with the best boots or shoes, it is still good to have Shoe Goo or something like it. This stuff sticks a lot better than melted soft plastic and you don’t have to plug it in. Thick enough to not run off, build it up smooth it with a wet finger. Plus you can fix a hole in the tent or tarps water can etc.

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