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Here is the context
I've got an old car for which I have a small plastic piece who is broken. As it's an old car and a very specific piece, I can't find it anymore. So I was thinking about 3D printing it.

My problem is this piece is on the carburetor, so close to the engine. This means, it can heat a lot, close to 90-100 °C.

My question
Do the pieces created with the common 3D printing techniques melt at 100 °C? If yes, what kind of other 3D printing technique can I use?

Here is the piece I want to recreate (sorry for the bad quality), the scale is in cm. The piece

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    $\begingroup$ That depends on the used material for the print. You might be more interested in the glass temperature though, these range from 50 to 160 °C from PLA to PEKK, note that the higher glass temperature plastics are hard to print on home 3D printers (requires bed and enclosure heating over 150 °C). $\endgroup$ – 0scar Dec 13 '19 at 12:42
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The number you're looking for is the glass transition temperature (the lowest temperature at which the material can flow or warp), not the melting point. This depends on what material you're using; approximate temperatures for common printable materials are:

  • PLA: 60˚C
  • PETG, high-temperature PLA: 95 ˚C
  • ABS: 105˚C
  • Nylon: typically 70˚C or above ("Nylon" is a large family of similar polymers)
  • Polycarbonate: 145˚C

Any plastic under your hood is probably either nylon (for its durability, impact resistance, and chemical resistance) or ABS (for its strength and heat resistance). These are both difficult materials to print: ABS emits toxic fumes while printing, and tends to warp if you're not using a heated enclosure, while nylon readily absorbs water from the air, causing the filament to bubble as it's printed. Further, many printers can't handle the high temperatures needed to work with these materials.

If you're going to print this yourself, I recommend using PETG and inspecting the part after a few days of use to see if it's warping. PETG is reasonably easy to print and comes close to your target heat resistance.

If you're going to get someone else to print it, I recommend using ABS. It's probably what the original part was made of, and anyone willing to print ABS for you will have the heated enclosure and ventilation system to deal with printing it.

I'd avoid polycarbonate unless you know the original part was made of it. Although PC is strong and heat resistant, it's also somewhat brittle and vulnerable to scratching.

High-temperature PLA is also brittle, and requires a heat-treating step that will change the dimensions of the part. It will likely take several tries to get something that comes out the right size, and even then, you risk having the part break when your car hits a bump.

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  • $\begingroup$ Thanks, it's exectly what I was looking for. The original part is brittle (that's why it's broken), so it was maybe made of polycarbonate. Is it hard to print? Otherwise I'll do it in PETG. It's the cooling water who is close to 100 °C, so it should be less for the part $\endgroup$ – Phantom Dec 14 '19 at 16:30
  • $\begingroup$ PC is very hard to print with and very abrasive. $\endgroup$ – Trish Dec 14 '19 at 18:25
  • $\begingroup$ @Phantom, polycarbonate requires high temperatures to print, beyond the capabilities of most consumer-level printers. $\endgroup$ – Mark Dec 14 '19 at 21:10
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Depending on the exact mechanical load and material used to print, you might get away with 100 °C.

Next to the melting temperature required to print the material (which will always be substantially higher than the maximum useable temperature!), you probably also want to have a look at the glass temperature of your specific material. Around that temperature your material becomes soft (rubber like) and can deform permanently when cooling down again. Chances exist that under a considerable mechanical load, the part will deform at even lower temperatures.

Maybe it would help to post a picture or describe the exact component you're trying to replicate. It might help in finding an alternative solution. (E.g. carving out of say PEEK to say anything.)

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I only use an ingeo 850 or 870 PLA that have different melting temp and more resistant the normal PLA. It's a lot easier to print with a normal desktop consumer printer then ABS or NYLON Doesn't have the same characteristics as a nylon filament but it can be used inside a car, I have used to print some parts for my car.

https://www.natureworksllc.com/~/media/Files/NatureWorks/Technical-Documents/Technical-Data-Sheets/TechnicalDataSheet_3D870_monofilament_pdf.pdf?la=en

(sorry but it's in spanish but a termal test)

Another option is to make a mold with the 3d printer and use a high temp resin

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You might want to check out printing with nylon. It's not typical of most 3D printers but you could always have it printed with a printing service, since it's a one off part. They can withstand a good amount of heat.

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  • $\begingroup$ Do you have the melting point of nylon? It might be an idea to edit and add that bit of info... $\endgroup$ – Greenonline Dec 13 '19 at 15:28
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Have the part commercially printed in metal.

I haven't used a commercial 3D print service so I can't recommend one, but I know there are many out there and the prices are reasonable. For example, I found that if their terms of service did not prohibit weapons, I could have had Shapeways print magazines for my FX air rifle in gold plated, hand polished stainless steel for less than FX charges for one machined out of aluminum.

So, print the part yourself in whatever material you have available to ensure that it fits and operates correctly. Then upload the file to a company that can print it in metal.

A possible DIY alternative, depending on the shape and size of the part, would be lost PLA casting. Hobbyists usually do this with aluminum.

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Nylon is probably your best bet. It is resistant to some chemicals as well. Figure on printing it around 250C.

It might do the job.

https://www.matterhackers.com/3d-printer-filament-compare

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  • $\begingroup$ What does the link add to the answer? $\endgroup$ – 0scar Dec 13 '19 at 23:57
  • $\begingroup$ It might be a link to a useful contrast of various 3d printer filaments. $\endgroup$ – EvilTeach Dec 14 '19 at 0:04
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    $\begingroup$ Please introduce the link if it is relevant for the question. As it is now it is just a loose link. $\endgroup$ – 0scar Dec 14 '19 at 9:06
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I would take a different approach. I would use brass or copper, machine it on a lathe to get the two diameters (you need to start with a thick piece so you are left with reasonable wall thicknesses), or, alternatively, use spin-forming to enlarge it to the diameter needed (works with copper, and you can use normal thin-walled pipe because you are only re-forming it, not cutting anything away), drill a hole in the side, thread it, and use a die to create a thread on the insertion pipe. then I'd screw it it, and finally solder it into place with a high-strength (lead-free) solder. The threading helps reduce stress on the solder joint; I can imagine it would crack a straight solder-only join without much usage at all. That right-angle joint of small diameter is going to be the weak point. It is the most likely place to have it snap, or start delaminating. That part was probably injection-molded as a single piece, reducing the effects of stress and eliminating any consideration of delaminating.

Note also that some of these parts have been computer-designed to precise dimensions, and a slight change in the ID of the side-pipe, or even its OD, might make a drastic change in its behavior.

If your only tool is a hammer, all your problems look like nails.

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