Is PS_ON controlled by a thermal error?
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Notice that part of the quote from e3d where aluminum blocks begin to lose integrity above 350C and the sock cannot be used above 300C? So maybe your suggestions for people should be if you do not own a copper alloy heat block from e3d then you should not be using a 40W heater for safety reasons.
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With that note, by upgrading my system to duetwifi and macro capability I am able to hot swap hotends from single extruder to dual extruder etc… for myself there is no reason i cannot print a another carriage that has a 30W heater so it is only powered by 40w when printing above 330C... now thats a good safety feature... lets brainstorm some more good ideas like the origional posters idea and this one.
I am sure there is more that can be done
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don't mean to be a butthead but… I don't want the machine limited by safety! if i can get parts that will work above 300C, i should be able to get safety at that level. Too many new filaments coming out and i can easily see the need to exceed 30 watts just for the high tech filaments that are in my future... These 2 items should be addressed separately. Safety is always a concern but the machine has to function 1st. just my 2 cents... IE polycarbonite and even some carbon fiber stuff are prime examples.
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A couple more that benefit from 40w and copper block
Carbon fiber Ultem (PEI) Extruder Temp: 330 - 350°C (all-metal extruder)
Ultem 9085 (PEI) Extruder Temp: 330 - 350°C (all-metal extruder)
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Your replies do not say hay I dont disagree with that feature….
What? I said that I'm sure this request will get implemented, suggested implementing it (said "what about implement it anyway") and also pointed out how it could be done. I also never disagreed with implementing it, but if it helps:
I don't disagree with implementing this feature.
I have said it multiple times, and I'll say it again: My suggestion of 30w heaters is for the 99% of people that don't print over 330C. Quite simply, if you don't print over 330C, a 30w heater is the safest thing you can do because it covers every controller failure mode there is, including multiple FET failures (which the PS_ON feature would not protect against).
For the other 1%, those people that do print over 330C, I am certain that DC42 will implement the requested changes, he has already said as much. But in the meantime, I offered some suggestions as temporary workarounds. (Adding a FET, implementing a temporary firmware change).
Maybe instead of finding reasons for why people shouldnt use powerful machines, we brainstorm some ideas to create failsafes in the event that something does go wrong.
Agreed. But those failsafes take time to implement (so it is worth discussing interim measures) and no failsafe is perfect (so if you don't need 40w heaters, don't use them).
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agreed, steady as she goes… safely is a huge concern with my printer. current job estimates 60+ hours so no way to baby sit it that long. Fingers crossed LOL
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Agreed. But those failsafes take time to implement (so it is worth discussing interim measures) and no failsafe is perfect (so if you don't need 40w heaters, don't use them).
Agreed
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The safest method would be swapping the 40w for the 30W when you dont need the extra power, but we definitely need some safety baked in when we do. Molex quick fittings for the heater cartridge should make it so it is not such a pain.
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Heaters are $7, less in bulk. To get to $500, that'd be ~80 hotends worth of printers. Are you genuinely talking about 40-80 printers? If so, that large of a bulk order would likely move the firmware feature request up in the queue.
It's also not 100% failsafe like you suggest. Internal shorting of heater coils (happened once to me on a common silicone bed heater) can produce higher temperatures than intended. It also existed for some time before I realized it, giving an opportunity for a mosfet to latch closed. It's also not at all practicable in my application (my goals are engineering around some bed mass vs losses near the edges, which require a particular watts per square inch, and are at odds with the goal of designing for a maximum attainable temp. I have a custom made bed that would need to be changed, as well as my goals for that bed.
If I must do a firmware modification myself, I will. Luckily I have the skills to do this. Many people don't.
My suggestion is to add a common and easy to fast track the additional layer of security for if all the others fail.
A second fet requires a board modification that many users are not confident doing. I'd really much rather not make modifications to a perfectly working brand new board. It's an easy modification, just need to tap into the Gate signal, but still, I don't see this as a replacement for my suggestion. Infact, I may end up doing both, thermal fuses for this application are tricky to do well.
I'm still requesting that if there's a compromise we can come to that can result in this being implemented for everyone across the board faster, we should do it.
What do you all think about an Mcode that allows you to request the reason for a power-off event if you weren't connected to the machine to observe the gcode window?
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It's also not 100% failsafe like you suggest. Internal shorting of heater coils (happened once to me on a common silicone bed heater) can produce higher temperatures than intended. It also existed for some time before I realized it, giving an opportunity for a mosfet to latch closed.
On initial heatup, Duet boards provide a warning if the heater seems to be overpowered (temperature rising too quickly). So for your scenario to occur, a FET would have to fail during the same print as a cartridge heater failure. In 5 years of 3D printing I've never experienced or heard of a cartridge heater failure like you describe, and I've heard of maybe 1 or 2 FETs getting stuck on. The odds of both occurring during the same print… you're more likely to be hit be lightning, honestly.
It's also not at all practicable in my application (my goals are engineering around some bed mass vs losses near the edges, which require a particular watts per square inch, and are at odds with the goal of designing for a maximum attainable temp. I have a custom made bed that would need to be changed, as well as my goals for that bed.
A bed should never be capable of reaching autoignition temperatures. If you're after a super powerful bed in order to overcome thermal mass and keep reasonable heat up times, I would counter that the proper engineering solution is not bed thermal mass, it is to use a heater that has a higher power density near the edges like E3D's Varipower bed or Prusa's MK42 bed.
A second fet requires a board modification that many users are not confident doing. I'd really much rather not make modifications to a perfectly working brand new board. It's an easy modification, just need to tap into the Gate signal,
The number of people that can't solder but are printing PPS/PEEK/PEI has got to be like, 1 or 2. I'll solder in a second FET free of charge for anyone in the world that sends me their board because they're printing those materials but can't do the soldering themselves. Or if you didn't want to solder at all, just set the firmware to use one of the heater pins on the expansion connector, and use it to control two FETs in series.
but still, I don't see this as a replacement for my suggestion.
That's good, because it wasn't intended to be a replacement for your suggestion - it is an interim measure until your suggestion can be implemented.
What do you all think about an Mcode that allows you to request the reason for a power-off event if you weren't connected to the machine to observe the gcode window?
And where would that power off code reason be saved in the meantime? That's where it gets a little more complicated and gets into the logging David talked about. Sure it is possible to hack something in temporarily, in fact that is what I suggested myself much earlier in the thread! But one of the things RRF excels at is avoiding the sort of "temporary" hacks that Marlin does that end up becoming poorly implemented permanent features. So it is better to do it right the first time, even if takes a little longer.
I feel like I'm losing my sanity discussing this. So I'll leave it at what I've said above, hopefully my suggestions are of use to someone.
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I'm also wanting to help protect people that buy cheap printers that have too powerful heaters and don't know better than to solve that. There are use cases for this feature than just the people printing high temp stuff.
2 fets in series doesn't solve it either actually. You won't have any indication that the first has failed and latched into the on position, and will keep on using your backup. The second can then do the same maybe years later. A good safety valve needs to 1) work, and 2) let you know that it worked.
Cartridge heaters are not the only heaters in use on printers. The bed won't reach autoignition temperatures for the filament, but it can cause other effects like breakdown of insulation and release of adhesives which can then grow into a bigger problem, with the heater not heatsinking into a big plate. Bed mass is a necessary function of the flatness and rigidity that I'm going for over about 2 square feet. I can share my CAD simulations if you like but justifying my choice in heater wasn't really the point of this thread. Stopgaps aren't either. Again, you're suggesting I do a bunch of machine rework on an already excellently performing machine as a stopgap measure.
The more obvious stop gap measure is to go back to a board that has this feature that I already have in stock, but I actually like the duet and I'm hoping we can help more people than just me!
A nice bonus would be to pause the host, turn off the stepper drivers, and turn off the remaining heaters too.
You need to supply 5v power to make best use of an atx supply anyway, how else will you turn PS_ON on? It can just stay in memory till retrieved. That's a far lower technical hurdle for people already using atx power supplies.
