Injection Mold Machines

[bostonman]

Long story short, recently I acquired old C64 joysticks and discovered an intermittent connection at the strain relief next to the base of one joystick.

Obviously the strain relief needs to be cut so I can remove the damaged section and resolder the wires.

The ideas I've had are basically ones already listed online (use heat shrink, etc...) but I also have a roll of TPE 3D filament.

Ideas I had was to 3D print some sort of strain relief and slide it over the wire. Another idea was to 3D print a mold and pour some two-part epoxy, however, doubt I can get it watery enough to flow throughout.

Most injection mold machines are at least $300 and I don't see myself needing this often enough to spend the money, so I was curious if anyone has better ideas.

[jpanhalt]

Michael Drela (aeronautical engineer and noted model sailplane designer) recommended MGS epoxies.  They begin as water thin and can be thickened with fumed silica to any desired viscosity.  I use them then when I need something really thin.  West Systems is good, but is more viscous to begin with.

[thm_w]

I can't tell from the photos online but the C64 controller appears to already have a strain relief on the cable, and probably has an enlarged cutout on the case.
That would mean printing a TPU piece and having it sandwich in the case should be possible. Can glue the cable to the TPU if you need to or just ziptie inside.

[DenzilPenberthy]

You could try this mouldable rubber. There's a picture here under 'How to Mould Precise Rubber Parts' and a short article describing someone re-making a moulded strain releif using a 3D printed mould.  Annoyingly though, no pictures in the article.

https://sugru.com/projects-inspiration/tech-gadget

If you're not fussed about it looking original, you can just mould the rubber by hand to make a strain relief over the cable.

[bostonman]

I can't tell from the photos online but the C64 controller appears to already have a strain relief on the cable, and probably has an enlarged cutout on the case.

Mentioning the C64 joystick (TAC-2) was just for conversation as my question was more about ideas for injection molding.

Using TPE seems like a good solution. A few weeks ago a roll arrived that I ordered, and, for fun, I printed a gasket I downloaded from Thinigverse. The gasket is not only flexible, but very strong.

At some point I'll spend time tinkering with creating a 3D model of a strain relief.

[Kean]

Most injection mold machines are at least $300 and I don't see myself needing this often enough to spend the money, so I was curious if anyone has better ideas.

Maybe you need to clarify what you mean by an injection mold machine.

A traditional injection molding machine is certainly more than $300... by many factors.  Even a just machined mold will typically set you back 10x to 100x that.  I was sad to have to have some of my molds scrapped after production considering what they cost, but I also couldn't justify another production run or having them sitting idle on a shelf in the factory any longer.

There is low pressure molding systems, typically used for overmolding of cables or handles.  I think this must be what you are referring to, but I don't think I've ever seen one of those offered for such a low price either.  They do not use the term "injection molding" to make it clear they are for low pressure overmolding.

[bostonman]

One was purchased at an old job for about $600 and was very small. I don't remember much about it, but it was a tiny business (maybe out of the owner's home) and didn't come with any molds.

Recent searches showed a few that were in the mid $300 range, but, as you pointed out, these aren't the large industrial ones.

The one at my old job was basically a bench top press where pellets were poured on top, melted in the tray, and, once liquified, you'd pull the handle. It would then force the liquid into the mold using the pressure.

It was a very simple unit, but clogged easy.

[kosine]

I used to have a Travin benchtop moulder many years ago. They sometimes come up cheap on ebay. Not hugely controllable, but it worked.

You also need a rigid CNC machine to make aluminium moulds, not one of those cheap plotter type devices. (Though you might get away with it if you go really slowly.) A modest hobby milling machine can be had for a few hundred, and they're not too hard to retrofit for CNC.

Takes a while to learn the ropes, but you can do injection moulding in a shed if you really want to. Only suitable for very small components, though. If you want anything larger you're going to need a proper moulding machine which start at a few thousand even secondhand. They mostly need 3-phase also, so not really practical for home use.

Another approach is to find a small local mould shop and get to know them. The greybeards are usually thrilled that someone is interested in the topic! If you could sort a hobby CNC out and make small moulds, they might be willing to run them in one of their machines. Just need a bolster mould you can bolt them to. I've run home made aluminium moulds not much bigger than a matchbox this way on proper industrial machines. (You have to manually extract the parts after each cycle (20-30 seconds or so), so you need to factor that into the design. Ejection systems are a lot more complicated and not worth the effort for short-run parts. You can do overmoulding this way too.)