Housing and extra fire protection for the X5S

Every 3D-Printer is a fire hazard. Just like a flat iron or a soldering iron or a tealight.
But those are not running your multi-day-prints. And as I mentioned fireprevention only briefly in my upgrade list, it’s time to post some more details about what I did.

A quick search on hackaday.com lists not only some examples of fires ([1] / [2] / [3] / [4]), but also solution approaches ([5] / [6] / [7] / [8]). If you prefer to be exposed to a constant stream of moving pictures and sound: Thomas Sanladerer also made two videos (hardware and firmware) on the topic. And there are even categories in webshops exclusively for “A8 Fire Protection”.

My own experiences are limited to the burnt connector of my self-built heatbed-MOSFET module. The connector itself was an oversized european one, but apparently I overlooked some verdigris (copper rust) on the ends of the speaker cables I used to connect the HBP. The flame-retardant connector housing did it’s job to contain the damage – and after a few hours of printing the smell had me searching for it’s source.
The commercial MOSFET module had arrived in the meantime anyway, so I could exchange those. And renew the ferrules on the cables.

There is (of course) a smoke detector in the cellar, where my 3D-Printer resides. You can’t justify going without that – and (at least in Germany) it’s mandatory to have them in rented housing space anyway. A connected one would be better, but this one is standalone. An old extinguisher is also placed near the printer.

The Marlin features (MINTEMPs, MAXTEMPs, THERMAL_PROTECTIONs) are in place and working. And as Tom’s 3D already mentioned: They are also useful as early warning systems. Just recently I threw out a pair of Phoenix “FKC 2,5” connectors and replaced them with Wago 221s. Something around the FKCs (ferrule? cage clamp?) had degraded and the hotend couldn’t surpass 255 °C anymore. Now it works flawlessly again.
Mark Rehorst: Thanks for the hint, that it would be a shame to use the 221s in junction boxes only.

Should my OctoPi freeze during the job, another Marlin firmware feature will kick in – at least, if I sliced the object with my personal Cura settings: The inactivity shutdown will shut down the printer, if the ‘Pi stays silent for too long.

Start G-Code:

M85 S60 ; Inactivity shutdown: 60s

End G-Code:

M85 S0 ; Disable inactivity shutdown

There is also a relay board connected to the GPIOs. The OctoPrint-PSUControl plugin will shut down the X5S once temps fall below 50 °C and you leave it alone for half an hour. And you can use the OctoRemote App to directly switch power from you Smartphone.
Retrospectively: Automatically separating the printer from the mains provides the largest amount of peace of mind for me.
(Note that the mains plugs were not connected to anything, while I tested the naked board in that middle picture below.)

As you can see in one of the pictures above, I also purchased one of those throwable fire extinguisher balls. Should it get hot enough, it will (hopefully) release a cloud of fire fighting agents.

As we had renewed a ceiling last year there was gypsum board (plasterboard / drywall) left – so why not place some between the printer and the old kitchen cabinet, where the X5S found it’s place? It should be a lot more fire resistant, than the worktop.

At this opportunity I also mounted new feet with some leftover (Ikea Kallax) felt pads. The Prusa printers had some problems with vibrations showing on the printed objects (look here, here, and here), because the the stock (soft) rubber feet were not damping the critical frequency.

What I did was altering HyperCube (2020 Extrusion) Anti-Vibration Foot by superjamie to fit my pads:

extr = 20; // extrusion
thic = 1.6; // thickness of plate
targ = 25; // target height
ht = targ-thic;
diam = 39.5; // diameter of base plate hole

Afterwards the X5S had gotten a bit louder (again), so they seem to do their job.

As I already worked on my own gantry (look here and here), I wanted a bottom plate to carry the PSUs and the controller case, when I move the whole printer. So I also designed adaptors to hold another plate of gypsum board there. You can find it on YouMagine and Libre3D.

But work on the CoreXY gantry had to wait, as I was informed about another problem:
As I had cranked up print speed to the limit of the hot end, added linear rails and now also the hard feet, the whole machine could now be heard not one, but two storeys above!

At that time I was still using the red stock board with the Shenzhenshi Yongfukang (“Heroic”) HR4982MTE stepper drivers. After changing over to the SKR with TM2130s, noise wasn’t a problem anymore – but the housing I hacked together from leftover chipboard and metal brackets had more benefits, than sound damping.

As a few screws into the old cabinet didn’t matter, I fixed it to that as an attachment.

For the interior I scratched together whatever looked like it could absorb noise and glued or screwed it to walls and ceiling.

At first I had the filament just passing through a hole from my drybox. But at some point I wanted something to connect a reverse bowden tube to. (The carriage should pull at the spool, not the extruder.) So I made this flanged feed through adaptor. The counter part at the carriage is the “TITAN_ADAPTER2.stl” from CONNECTOR ADAPTER by ichibey, zip-tied to the drag chain.

The feed-through adaptor can be found here on YouMagine and here on Libre3D, but after I designed my own “Slim Anti-Tangle Dual Spool Holder” for IKEA 365+ 10.6l-containers (YouMagineLibre3D) I migrated to just using multiple longer tubes and directly changing them at the carriage. The hole in the side wall is now open and all reverse bowden tubes enter here simultaneously.

But there are also times, when the “proper” solution with drybox and filament guiding tubes gets in your way…
Very soon after installing the enclosure, I had to improvise a spool holder out of two spools (Yo Dawg!) and a broom stick. And then along came a 2.5 kg spool of PET and the stick was too thick. So I replaced that with a pipe. And finally I made some space-saving hooks to prop that pipe up in Tinkercad. (If anyone without an Autodesk-account wants that STL, just drop a comment here – but also tell me the key word for others to find that type of hook then…)

So my X5S now sits on top of a fireproof plasterboard, next to an extinguisher ball, but on the other hand I put more wood and (I guess combustible) foam around it. The tricks, that let me sleep well at night are still mostly done in firmware and via OctoPrint.
I have added overly complicated filament guides – mostly due to the moist air in the cellar.

But there is another, huge benefit from all the tinkering now: The machine now can print large ABS parts warp-free. 🙂
That’s done simply by wrapping a picnic blankets with an “insulating” (metallic) underside around the housing and putting two huge metal parts on top of it, so it stays in place. Heating up the 330×330 mm² HBP to 110 °C then gets the interior warm enough – even though there is a gap at the bottom. (Maybe the power supplies enjoy that gap, since the 24V one powering the build plate really gets to break sweat then…)
The Prusa guide on enclosures also suggests a “photo studio tent” would suffice, BTW.

After a bit of testing with PC-ABS and ASA, I also found a design flaw in my X-carriage – and a fix: The airflow cooling the hot end gets directed downwards. But a piece of cardboard can easily block it, so the layers stop delaminating mysteriously.

And BTW: The Petsfang is an absolutely great part cooler. But on the first layer it’s only 1 mm higher, than your build plate. And it melts under ABS conditions (HBP at 110 °C, hotend at 260 °C, no airflow through the fang). At least, if it’s printed in PETG. Guess my next carriage (I’ll change over to that BMG clone and a V6 with threaded heatsink on occasion) will move into the “High Clearance Fang” direction again.

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