We’ve said it before and we’ll say it again: water always finds a way in. That’s particularly problematic for things like wire splices in damp environments, something that no amount of electrical tape is going to help. Heat shrink tubing might be your friend here, but for an electrically isolated and mechanically supported repair, you may want to give over-molding with a hot glue gun a try.
The inspiration for [Print Practical]’s foray into over-molding came from a video that’s making the rounds showing a commercially available tool for protecting spliced wires in the automotive repair trade. It consists of a machined aluminum mold that the spliced wires fit into and a more-or-less stock hot glue gun, which fills the mold with melted plastic. [Print Practical] thought it just might be possible to 3D print custom molds at home and do it himself.
His first attempt didn’t go so well. As it turns out, hot glue likes to stick to things — who knew? — including the PETG mold he designed. Trying to pry apart the mold after injection was a chore, and even once he got inside it was clear the glue much preferred to stay in the mold. Round two went much better — same wire, same mold, but now with a thin layer of vegetable oil to act as a release agent. That worked like a charm, with the over-mold standing up to a saltwater bath with no signs of leaking. [Print Practical] also repaired an iPhone cable that has seen better days, providing much-needed mechanical support for a badly frayed section.
This looks like a fantastic idea to file away for the future, and one that’s worth experimenting with. Other filament types might make a mold better able to stand up to the hot glue, and materials other than the ethylene-vinyl acetate copolymer found in most hot glue sticks might be explored. TPU over-molds, anyone? Or perhaps you can use a printer as an injector rather than the glue gun.
Why don’t you just 3d print mold to make the mold and cast silicone in it? that way you’ll never have to worry about hotglue sticking to it, since it does not stick to silicone…
Greasing it up for 1 wire is probably easier.
Or just 3D print a mold, fill it with hot glue and leave it that way?
Print out another mold for the next cable.
That was my immediate thought. The mold is cheap to begin with, so leaving it in place won’t break the bank. And it could probably be cheaper still – if you don’t have to try to peel it off, you can make it thinner.
I’ve sealed wire joints by applying hot-melt glue, then applying dual-wall heat-shrink tubing. The inner wall is essentially hot-melt glue anyway, and when you shrink it with enough heat the hot-melt that you applied directly to the wire melts as well. You end up with a strong bond and a really good seal. Of course, that only works if you don’t have connectors to big to slip the sleeving over.
Speaking of heat-shrink, I often stretch it if I need to get it past a connector. I cut the heat-shrink to length, then shove one end over the tip of a long-nose pliers and pull the handles apart. I repeat that at the other end and then slide it over the connector. It’s surprising how much that stuff will stretch before it breaks. You need to work fairly fast though, or it will shrink again before you get it past the connector.
Ooor 3d-print the mold, fill it with hot glue, use isopropyl alcohol to release the glue from the mold
Or use the (annoyingly expensive) soluble-support filament.
Or make the mold with break-off lines, for destructive removal. For one-off jobs it’s good enough. Works also for silicone castings; a hybrid rigid-rubbery part can be done by integrating the moulds as thin layered structures; print, cast into, peel after curing.
Or just freeform the overmold, using a small torch and smeared-on hot glue flame-melted straight on the stick; that’s excellent for improvisations and field repairs. Flame-etching the substrate before applying the glue will also help with bonding.
He measures no conductivity between one end of an INSULATED wire and the saline solution, and from this concludes that the overmolding is waterproof? That’s a head scratcher.
That was the first wire, the second wire was bare
I did this quite a few times with just aluminium foil to create a mold around the wire which is then filled with hot glue. Works ok. Looks ugly. Improves wire shielding by 1u%.
Its funny how these cables by Fruit-company always have broken insulation and worn out black connectors. My better halfs cables look exactly the same. My own cheap ass USB-C cables look perfectly fine after several years of usage.
Yup…
I found a few deals here and there for passive thunderbolt 3 cables and they have been going great for 3 years now.
They may only be 3 foot long, but they are basically the only way I have found to get a cable with ‘all of the wires’ inside it to support all of the goofy combinations of usb-c and displayport alt mode, etc, to work with all my devices and docks.
…I should have bought a dozen more when they were $9/ea.
I am not a cheerleader for apple but in my limited use of their stuff, their cables hold up well. I have lots of old hp and dell cubes that I have had to cut bad pieces out of near the connector. I think any cable that you use every day that gets tugged on and flexed is not going to last forever. My current Dell cable, the black over molding on the connector fell off so the whole thing now glows bright blue and not just the “ring” and it looks like the clear plastic is starting to give. I need to find the black pieces and next time I pop a tube of superglue use a drop to hold that mess together as well as whatever else I have cued up for gluing.
It’s the very thin cables on ipods and iphones that tend to have trouble. Very much like the picture, they bend too much near the end and wear out. You have to treat them much more gently than other cables, if you want them to reach a good lifetime. They’d probably be fine if they were wrapped in something a bit stiffer/stronger for a few inches near the end.
It’s funny how people say this, as I’ve found the opposite. I’ve never had an Apple-made cable fail. I’ve had a few cheap knockoffs fail, and lots of cheap USB-mini/micro cables fail, but almost always it’s the poor quality connectors or how the cable is molded into the connector.
I’ve had one Apple MacBook power cable fail… that was lent to a colleague and within 2 months wore through… very odd, as that’s what happened to her previous one…
I’ve never had a USB-C cable fail, but I’ve got a few that only work one way round… different issue…
In conclusion, I suspect 90% of the issue isn’t the cable, but the person. Some people are kind on cables, some aren’t.
Well you are only comparing the cheap crap to the cost a few kidneys per cable ‘premium’ Apple ones there… So its not a shocker when you paid a few squid that they are all crummy and fail quickly, if you manage to actually buy good quality for the other cables they just last into the forever or one really stupid brain failure moment that nothing survives in my experience (at least before USB-C*). Though actually knowing what you are going to get as its not what the cable looks like in the picture, and the price isn’t always representative of the actually quality.
But still Apple has always insisted their cables are worth IMO something more like 3x what they are by the quality, at least in comparison to the genuinely good similar capability cables.
* as that spec is a mess of epic proportions anyway, so odds are great that the cable isn’t actually going to do what you need if you actually need more than USB2. And when you do need all the bells and whistles that is lots of conductors required, thus making for a much stiffer cable or a much much more delicate cable as the conductors must get thinner and thinner.
I have found Apple USB cable are indeed that bad. The strain relief tends to crumble away if flexed more than a few times.
The cheapest of cheap cables manage to outlast Apple cables. Now if only it was possible to reliably buy cheaper cables that are wired correctly.
Isn’t there something here about Apple not using PVC cable jackets for environmental reasons? Might be other factors too, but I seem to remember that PVC jackets are the most durable, but also the most environmentally damaging…
You’re right! All the Fruit connectors have cracked over the years. It’s that shiny slick hard white plastic, it does not stand the test of time.
I have shrink wrap on most of them, but that only works for a while, because it’s shiny slick plastic…
It could be that your fruity cables actually follow the USB guidance that the cables be the weak point so as not to damage the much harder to fix jack on the actual device.
The cheap ass cables are probably stronger than they should be so they can sell it as a “feature” to those who don’t know any better.
I use Sugru for this sort of thing. Quick, easy and works a treat.
Me too. I used Sugru to fix a Thuderbolt Display’s cable. It’s especially important because the cable on these displays is single-ended. If it fails, that’s it short of tearing open the display and replacing the cable.
I wish I’d thought of printing some sort of shape to overlay. While functional the strain-relief I molded onto the cable is asymmetrical and has my fingerprints in it :)
“Heat shrink tubing might be your friend here”
Especially the sort with glue inside.
Exactly. I see no need to reinvent wheel.
Definitely, and if you don’t have it, simply spread a light amount of hot glue THEN apply the heatshrink tubing over it
Or just don’t buy garbage apple cables :)
I have a pair of cheap wired headphones that sounds very nice (to me) but I got tired of replacing the cable or the 3.5 mm connector from time to time so I removed all the soft rubber of the original connector and after soldering everything I coated it with a mix of superglue and baby powder until I got a decent size for easy grabbing and pulling, so the thing is working fine since 2018. The down side is that people who see your DIY connectors are like: aw, this poor guy has no money to buy nice gadgets, I will give you one for free , gggrrr! So anyway I’m big fan of using DB9 connectors for everything :)
It always surprises me how we got used to think using small connectors is fine, tiny usb connectors, tiny sd card slots, tiny screens, tiny keyboard and so while usually the approach in industry is to use robust connectors and big buttons ready for rough environments. I remember when I was working on oil rigs in the middle of the Gulf of Mejico we used to install big water/explosion-proof panels for gas monitoring, they where sealed boxes with a big crystal in the front and the screen just behind it, all the ‘buttons’ where magnetic so we must to carry a tool hanging on our necks, it was a pencil with a magnet on it. People used to joke that boxes and the pencils would be the only remaining in case of a blowout. Damn I want to go to the beach now!
While DB connectors are great, what about GX aviation connectors ?
Imagine an Android or iPhone with a DB15 or 12 pin GX-25
And don’t forget the rugged case! damn that would be rad! more like a cyberpunk thing, but we all already live in a cyberpunk world so it can be done. :)
Ask any roofer, water is very thin.
You should buy yours in a more reputable bar
LOL!
Contrary to the statement in the first paragraph of the article, hot glue has a significantly greater water vapor permeability (roughly five times worse) than vinyl of decent quality, assuming the same thickness.
Molded hot glue probably makes a better looking covering, and maybe a stiffer sleeve, but it isn’t necessarily better protection from water.
And woe upon thee if that hot snot gets splashed with IPA.
We use scotchcast poured into a greased mould for splicing cables that connect the instruments that go on ROVs. These can go down to hundreds of meters. The wires are stripped, soldered and two layers of heatshrink applied – one over each solder joint and one over the assembly. Lightly sand the outer jackets of each cable that goes into the mould. Then we put the joint into the greased mould and pour in scotchcast which is a two part epoxy. The moulds are supplied with the scotchcast. Trim the ends off the mould to fit the cables. Takes a good few hours for the scotchcast to set. I can’t comment on the insulation and waterproofing properties of scotchcast vs hot melt glue. Hot melt glue has the advantages of setting quickly and being cheap and available.
A nice professional solution. For DIY I wonder how JB Weld 2part or even their putty stick would work for this.
So sorry that the only lubricant you had on hand was vegetable oil…
Would take a bit more work to print and make a negative mold first, and it would be more fragile/possibly a one use, but got glue doesn’t stick all that well to plaster of Paris if I remember correctly
Good hack for already constructed wire assemblies, for individual wires consider adhesive coated shrink tubing. Been using that for decades to waterproof connections.
I’ve also injected hot glue into 9 pin D housings in use cases where stain relief has proven less than stellar.
Check out Robin Renzetti’s technique for this
https://youtu.be/JU2jsbGNcZE
Uses a variant of “Shoe Goo” urethane and toluene
Do something similar with putting unmelted hot glue into a mold that’s wrapped in heat shrink tubing and heat with hot air gun, shrinking the tubing forcing the melted hot glue out the ends (trim it later).
From what I can tell totally waterproof.
While this looks nice, and heat shrink is better, a proper waterproof splice technique using stretched scotchfil covered by scotch 88 tape would have vastly superior waterproofing (I’ve opened pump splices that had been submerged 40 years in a well that were pristine). They only take a minute to do with no tools and offer nice strain relief, BUT I will say they are bulkier and aren’t pretty like this. :-)
Sugru or Liquid Tape have been around for a while now
Melted plastic may stick to things but that doesn’t make it a proper glue-adhesive. Without any strain it seems to come off all on it’s own after a few years.
Most glues will make a better seal if waterproof. If same plastic could be fused to the insulation’s plastic that would win.
I’d used hot glue for 30 years to make strain reliefs for cables, but lately when my company needed to prevent cable head breakage, our ME designed shell mold for all of our cable heads that we print in PLA. The molds get a light coating of mold release and the halves are screwed together and typically last 10 or more uses. We fill the molds with two part urethane that makes the strain relief a little flexible, waterproof and bonds to the connector to prevent broken wires from cable movements or vibration. We use a small amount of plumber’s putty anywhere where we don’t want the urethane to penetrate into the rear of the connector where the wires are soldered.
We have saved tens of thousands in tooling costs and cable molding fees by using this method.
This seems like a lot of work for something that won’t hold up as well as adhesive heatshrink. It’s not really worth the effort unless you use something better than hot glue.
Polycapralactone. Melt in hot water and workable like clay.
Marine heat shrink tubing is just the thing for this. Relatively cheap. Has adhesive sealant inside. Takes a couple minutes to do. I know from experience when you have a 3d printer everything can look like it needs a printed solution. But in this case it’s not the best method.