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I know that for printing some materials like the carbon-fiber filled PLA it's recommenced to use a steel nozzle since it'll wear-out a standard brass nozzle quickly. Is there any reason to prefer using a brass nozzle for 'simple' plastic-only filaments instead of just printing everything with steel?

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Thermal conductivity of brass is approximately twice as better than steel (not stainless). Given that the size of nozzle is relatively small, it should be able to transfer enough heat for a medium-speed prints at least. I have printed PLA and ABS using "steel" nozzle (brand of steel unknown) at the speed around 80 mm/s without any visible differences compared to brass.

However, an ideal nozzle (I see) is made of tempered bronze with polished inner channels. Bronze is known to have better friction coefficient and tempered one should be enough to resist carbon-type filaments more efficiently.

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    $\begingroup$ One caveat about brass nozzles, is that most have some small percentage of lead in them. IFF you're printing something that i meant for food, water, gardening etc, there could be some transfer to the printed part. $\endgroup$
    – Diesel
    Apr 13, 2017 at 23:30
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    $\begingroup$ Keyword is "small" here. Typical lead presence in brass alloys is not more than 3%. Let's say nozzle looses 1% of its weight per 1kg of plastic (very pessimistic view on brass). Nozzle weight is about 2.5g. This results in transfer of 0.0025 * 0.01 * 0.03 = 0.00000075 kg of lead per 1kg of plastic. $\endgroup$
    – Mikhail Z
    Apr 14, 2017 at 7:19
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    $\begingroup$ Agreed, miniscule percentages. But for making food grade products some people still want to know that there is a non-zero transfer..even if you're almost better off measuring number if atoms transfered. $\endgroup$
    – Diesel
    Apr 14, 2017 at 13:51
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    $\begingroup$ @MikhailZ, according to cdc.gov/nceh/lead/tips/water.htm, Lead concentrations in drinking water should be below the EPA action level of 15 parts per billion. That puts your (very extreme) estimates at 50x concentration of "safe" drinking water. Now, you also need to get the lead back OUT of the print into the food, and similar figures would apply - i doubt you would lose (and comsume!) 1/50th of the print per time that you consume from a print that weighs the same as the food being served! $\endgroup$
    – AndrewP
    Apr 19, 2017 at 5:10

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