Fuse Questions about Duet WiFi and Printer Fire Safety

  • Do I need to add 5A and 15A fuses to the hotend wiring and heat bed wiring respectively or is something like that already built into the Duet with mini fuses? Also can I use fast blow or does it matter?

    I currently have a thermal fuse under my Onyx heat bed and was considering adding a thermal fuse to the E3D headsink perhaps and the 15A and 5A fuses for extra safety measures. Opinions welcome on what other builders think of this. The Onyx heat bed comes in at 12A, so 15A should work and I believe the E3D heater cartridge is 3.3A so a 5A fuse (or perhaps a 4A?). Is the fuse formula 110% or something of the calculated amp usage?

    If anyone has or has not chosen to do fuses, let me know the reasoning behind it. I'm not sure if this would be overdoing it or adding extra safety precautions.

    Also, this might be a dumb question - but are there any 3D printer models that utilize two thermistors side by side to provide an extra variable to compare heat temps to for extra safety precautions? I was thinking this might be a neat feature and it could even monitor an extra temp (like outside and inside of the printer bed). I know currently the thermistors breaking causes a shutdown usually - but an extra thermistor would provide a fallback to continuing during long prints and a failure.

    On my paracord cable sleeving, I ended up buying Kevlar paracord and I resleeved my cables. I was holding a lighter to the Kevlar paracord and it takes much longer to even char and it does not seem to catch fire (for at least several seconds in open flame). You can only fit 2-4 wires inside the Kevlar sleeving, but it could potentially be a good material to sleeve everything in.

  • administrators

    The 12V or 24V power supplies used in 3D printers have output short circuit protection, so there is no real need for fuses on the output. If you are worried about hot end heater shorts then you could add a 5A fuse as you suggest, but I've never heard of anyone burning out a hot end heater circuit on a Duet.

    A bed thermal fuse is worth having if the bed can reach dangerously high temperatures if left on at full power. The same applies to the hot end heater, although it's harder to find thermal fuses with a appropriate temperature rating.

  • It seems the HE280 SeeMeCNC hot end uses a 98C thermal fuse in the heat sink area (it has a fin missing where the thermal fuse fits in between two fins). I might see if I can grind away part of a spare E3D heat sink and fit a thermal fuse near the top of the heat sink.

    I think you could also "cheat" and raise the max temp of a thermal fuse by wrapping it in silicone tape. Maybe on a future printer build I'll buy some spare fuses to see what temps I can break them at. I did kill one during this printer build by soldering too close to the actual fuse part.

    The photo is in Step 17 of the online guide for those curious: https://seemecnc.dozuki.com/Guide/HE280+Assembly/45

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