3D Printing replacement for Bakelite

[WaveyDipole]

For some time I have had a small variac that appears to work, but the Bakelite housing for the connectors is smashed. It held well enough together for a test, but is definitely unsafe to use in its current state. I de-soldered the connectors and removed what was left of the housing. The lid is a makeshift replacement which probably needs replacing as well.

Now that I am finally retired, and since I now have a 3D printer (Creality CR-X), I would like to make a replacement housing. It obviously needs to be robust enough and also handle having connectors with mains AC voltage running through them attached.

I have so far only had some experience with PLA which I have plenty of, but I already noticed that it can shrink a bit and warp with heat and UV exposure. My printer does not have an enclosure so I believe it can only handle PLA and PETG, despite having options for ABS in the menu? Are any of those materials actually suitable for the job, or will I be better off buying a ready-made ABS case?

[Radio Wrangler]

Make one in PLA, build a polished surface on it with paint, apply mould release agent and make a silicone mould from it. Cast a good hard epoxy resin in the mould. Don't worry about getting it out of the mould, you can just tear the mould off.

THere are firms will do this for you, if you pay. Look for prototyping services.

David

[jamesperrett]

Originally Posted by WaveyDipole

My printer does not have an enclosure so I believe it can only handle PLA and PETG, despite having options for ABS in the menu?

Are you sure that it won't handle ABS? My son has successfully done some ABS printing with his basic Creality Ender 3 printer.

[G6Tanuki]

My big worry with this sort of thing is whether the material used will have the necessary insulation characteristics to be safe with mains voltages, and will it be self-extinguishing to the requirements of the likes of Underwriter's Laboratories, ASTA, TuV etc.

[WaveyDipole]

Originally Posted by Radio Wrangler

Make one in PLA, build a polished surface on it with paint, apply mould release agent and make a silicone mould from it. Cast a good hard epoxy resin in the mould. Don't worry about getting it out of the mould, you can just tear the mould off.

Interesting idea. A resin case will almost certainly be more sturdy.

Originally Posted by Radio Wrangler

There are firms will do this for you, if you pay. Look for prototyping services.

David

Funnily enough, just read that in a magazine advert as well, but was not able to get hold of the magazine. I see quite a few entries in Google for "prototyping services". Will have to look at what's on offer and the cost etc.

Originally Posted by jamesperrett

Are you sure that it won't handle ABS? My son has successfully done some ABS printing with his basic Creality Ender 3 printer.

No, I am not sure, but that is interesting to hear. The Ender 3 is an open frame printer, but I have read that ABS requires an enclosure to maintain temperature of the material. Mine has had upgraded tubes added so it might well be possible to print with ABS. I just haven't tried it yet. I have held back because it doesn't have an enclosure.

Originally Posted by G6Tanuki

My big worry with this sort of thing is whether the material used will have the necessary insulation characteristics to be safe with mains voltages, and will it be self-extinguishing to the requirements of the likes of Underwriter's Laboratories, ASTA, TuV etc.

That was my main concern, but then you can't always be sure about that these days, even with items that you buy, although generally if you buy something from a high street shop or reputable supplier, then it ought to be appropriately tested and rated. With 3D printing materials, you also have the problem of rigidity and mechanical strength. PLA is quite soft and pliable yet the layered nature of 3D printing can make it come apart quite easily. I haven't tried PETG or PLA yet so can't comment on those, but I have doubts that PLA would be suitable. Even with ABS, injection moulding at a factory is going to produce different results to 3D printing, even if the end product looks very similar. So yes, its a bit of an uncertainty. Its one thing 3D printing knobs, cogs and dial parts, but another when something needs to hold conductors at mains voltages. Its one of the reasons I asked.

PS, this is kind of weird, but I have been typing about 3D printing filaments and now my Alexa is showing me adverts for PLA filaments? How does it know?

[Sean Williams]

PLA is Hygroscopic (Absorbs Moisture)

So, as an insulator it isnt fantastic.

PETG is better in that respect, though a little more fussy to print with, but it is stronger, and does not absorb moisture - I use it for many things, including antenna parts.

[The Philpott]

Forum user 'Ti Pwun' may know more about this subject.

Dave