How can I fabricate a custom one-off plastic part?

Question

Here's some background: I just moved into a house and am in the process of fixing up the bathroom. I want to keep the two florescent lights that frame the medicine cabinet but the plastic covers are probably 30 years old and one is cracking.

Question: Does anyone know of a place where I can send the one good light have a set of covers fabricated out of new plastic?

The lights look almost identical to this:

Answer 1

That piece looks to just be a single curve (bent in a single axis), so it's possible to do yourself, but it's not necessarily the easiest thing to do, and you can get some optical distortion depending on how evenly you flex it.

If I were to do it, I'd do the following:

1. Trace the inside contour onto a piece of wood.
2. Make multiple wood pieces, slightly under size, one for each 6" or so of the length.
3. Attach them all with some sort of stringer, or just mount down to a piece of plywood.
4. Stretch a piece of thin metal (look for aluminum flashing at the hardware store) over the plug.
5. Make sure the existing piece fits on the plug well, if not, adjust.
6. Secure the aluminum flashing. (I recommend contact cement or other adhesive so you don't leave dimples from nails or screws)
7. Get a piece of plastic the length you need, and maybe a tad wider than you think you need.
8. Get a few strips of wood the length needed, and some clamps.
9. Place one side of the plastic against the plug, and clamp in place (use the wooden strip, so you're not clamping against the plastic).
10. Using a heat gun, evenly heat the plastic at the curve, and slowly apply pressure on the unclamped side.
11. Once you get it bent, clamp the other side and let cool.

If you have a more complex shape, you can try to find someone who has a vaccuum table (or make your own), or find someone with a large enough autoclave.

And one other thing to note -- flourescent lights give off more UV than incandescent bulbs, so most shrouds for them are UV blocking.

Answer 2

In the UK there services popping up that offer profesional 3D printing

For example

3D Print UK

They offer help designing product and i think the max sizes are something like 2.5metres by 1metre.

They charge £2 per square cm of material used.

In order for it to diffuse light like you require you will need quite a thin print out (cheaper so that's good) but it is more brittle. You might find some locally by you that can offer similar services. These printing services are popping up all over the place.

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i.materialise.com US <- They can print in translucent resin, silver, gold, titanium and a bunch of other crazy materials!

I am not sure about design help but it seems they accept a variety of deign files.

Try and ask a traditional glass blower to do that for a few bux!

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And completely unrelated but since I am talking about it, 3D food printers! Yumm!

Answer 3

It is often the kind of thing that is hardly ever worth making, unless you have the equipment and the skills. As others have said, you will often spend more on the part than on new fixtures, especially if you add in your time to find it or make it.

Having said that, I'll also say that I've often made parts to replace a variety of things from plastic, from the handle on a well used kitchen pot to rebuilding the wheels and axel of a hand cart. It CAN be an interesting and fun problem to solve.

For your problem, I'd not be looking for a 3-d printer as others have suggested, but for a translucent thermo-plastic, that with some carefully applied heat and a form of the proper shape can be deformed into the shape you desire. See if you can find a piece of sheet plastic, then build a form. It won't be trivial to do, as it will be easy to apply too much heat, or too little. Perhaps an infra-red bulb or two will give you nicely distributed heat.

Answer 4

I think all of the comments are pretty spot on - unless a friend of yours has a large 3D printer, getting a single part made is going to be very expensive. Producing the part is actually not the expensive part, but building the molds used to produce the part can be VERY expensive. So expensive that often times a company might only have a single mold of any given part.

If you are really set on keeping the fixtures I think your best bet would be to try and find a similar fixture on eBay or at a used goods store and seeing if the covers would fit. Maybe find one a bit larger and trim to size.