Yes, 3D printers can go on fire.

I haven't loked at the source code, but could you use the proportional/integral/differential values from the PID control loop to determine if strange behaviour is happening? Negative P and D terms would indicate a failure. Alternatively the integral term alone may be enough, i.e. the temperature has been too low for too long.

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Antslake

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brnrd

I'm not saying that metal is not better. My point is that UL listed devices don't have to be in metal enclosures.

Perhaps my statement was too general, but when I wrote it I was thinking more along the lines of similar items, like power supplies, and 120v junction boxes. Obviously I am not an underwriter, but I did fire proof NYC hospitals for 11 years. We took them apart and put them back together again with the proper fire and smoke ratings. I do know a thing or two about making things safe in that department (when I apply it). All those devices you named are tested, and meet the requirements for their use, fire rating included. You obviously should not put a hair dryer under the sheets and fall asleep with it on. I also own a HVAC and plumbing business and deal with flame and fire all the time. Not just in the equipment but in the exhaust. It's just not a good idea to have a FET next to wood. I've seen to many go off like a mini rocket when they fail. Compile that with the garbage we get from China sometimes and it's a recipe for disaster. I had always had in the back of my mind worries about the wood frame. My plan was to upgrade it to metal. I am building a second i3 first, printed my own parts and looking for a metal frame, then I was going to upgrade this one.

So being that these things have gone up in flames for a few people, metal it is.

Personally I think all metal would be the best route even build a metal enclosure with high temp glass say from pellet stove around the printer you being the owner of an HVAC company this should be easy to fabricate and also I would include a thermal fuse on top of the print head assembly that's in series with a master relay coil you can get them in many electronics stores or on eBay many different temperature ratings. Here is a picture where a mounted mine looks like a resistor in photograph in front of the 2 x 4 box and in front of the adjustment nut and bolt a small device you see on the first two terminals of the top terminal strip

Edited 2 time(s). Last edit at 01/17/2014 08:35AM by cnc dick.

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tjb1
I'm pretty sure MINTEMP is just a thermistor initialization check and can not be used during printing because the printer would never start if this is within 5 degrees of extrusion temp. I think the feature you are thinking of is the min extrusion temp which just prevents extrusion and would not shut the printer off.

You are right and I realized it. I admit my mistakes - most of them anyways. I've edited my previous post so as to not provide false advice.

I really do think the firmware could probably be updated quite easily to have some "sanity checks" built into it such that if power is being applied (a dislodged thermistor would probably result in full current/power) then the temperature should be increasing or at least be within certain parameters. If it's not doing either then the firmware should go into a failsafe. That could all be handled by software changes and no hardware changes.

Thanks cnc dick.

As far as mmin_temp goes, would it be easy to change the code so that once operating temp is reach, min temp changes until print is done?

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umdpru

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tjb1
I'm pretty sure MINTEMP is just a thermistor initialization check and can not be used during printing because the printer would never start if this is within 5 degrees of extrusion temp. I think the feature you are thinking of is the min extrusion temp which just prevents extrusion and would not shut the printer off.

You are right and I realized it. I admit my mistakes - most of them anyways. I've edited my previous post so as to not provide false advice.

I really do think the firmware could probably be updated quite easily to have some "sanity checks" built into it such that if power is being applied (a dislodged thermistor would probably result in full current/power) then the temperature should be increasing or at least be within certain parameters. If it's not doing either then the firmware should go into a failsafe. That could all be handled by software changes and no hardware changes.

I agree, I had a thermistor fail at 310C and report temp swings of up to 130C and still kept running until I discovered it. I wish they would add a code like "If temp changes by X amount in Y time, kill printer".

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tjb1
I'm pretty sure MINTEMP is just a thermistor initialization check and can not be used during printing because the printer would never start if this is within 5 degrees of extrusion temp. I think the feature you are thinking of is the min extrusion temp which just prevents extrusion and would not shut the printer off.

I can't look at the code now but I'm pretty sure that the firmware would turn off power to the hot end if the reading goes below MINTEMP and above MAXTEMP at anytime. A disconnected thermistor would read as a very low temperature and a shorted thermistor would read a very high temperature. I think Marlin would require you to issue an M command or reset the controller when that happens.

Edited 1 time(s). Last edit at 01/17/2014 09:56AM by brnrd.

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brnrd

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tjb1
I'm pretty sure MINTEMP is just a thermistor initialization check and can not be used during printing because the printer would never start if this is within 5 degrees of extrusion temp. I think the feature you are thinking of is the min extrusion temp which just prevents extrusion and would not shut the printer off.

I can't look at the code now but I'm pretty sure that the firmware would turn off power to the hot end if the reading goes below MINTEMP and above MAXTEMP at anytime. A disconnected thermistor would read as a very low temperature and a shorted thermistor would read a very high temperature. I think Marlin would require you to issue an M command or reset the controller when that happens.

Those are not checked during printing though, I did not receive an error until I tried to restart the print and it went through the checks again.

Antslate,

I found a metal I3 frame at ultimaker

[ultimachine.com]

I would not rely on software for safety. It's too easy for a bug or power glitch to hang up the CPU. The more complicated that the control algorithm becomes, the more likely it is to have a bug. The CPU could easily hang with the heaters on.

In that case, a hardware circuit is the only way to ensure safety, but even there hardware failsafes need to be tested.

---

What is Open Source?
What is Open Source Hardware?
Open Source in a nutshell: the Four Freedoms
CC BY-NC is not an Open Source license

I agree. I just purchased some 240C thermal fuses from amazon. I'm going to install them somewhere near my hotend. I'd still like to see the software failsafes incorporated.

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umdpru
I agree. I just purchased some 240C thermal fuses from amazon. I'm going to install them somewhere near my hotend. I'd still like to see the software failsafes incorporated.

Looking at the 240C fuses on Digikey, it says the 240C is only rated to hold at 200C with max spikes of 240C which would be of little use with the all metal hotends and new materials. The datasheet mentions one peaking at 280C but still would like 325-350.

I agree the best bet for fire safety is a thermal fuse, and to keep away from flammable materials and gases, as well as anything that burns at the temp of the thermal fuse.

Edited 1 time(s). Last edit at 01/17/2014 01:14PM by jamesdanielv.

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tjb1

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umdpru
I agree. I just purchased some 240C thermal fuses from amazon. I'm going to install them somewhere near my hotend. I'd still like to see the software failsafes incorporated.

Looking at the 240C fuses on Digikey, it says the 240C is only rated to hold at 200C with max spikes of 240C which would be of little use with the all metal hotends and new materials. The datasheet mentions one peaking at 280C but still would like 325-350.

I realize that's not an ideal condition. I'm not printing with new materials yet and so don't need to go to real high temperatures yet. For me, the solution is to put a thermal fuse directly on the heater block. I plan on installing mine on the cartridge heater wiring about half-way up the PEEK insulator on my J-Head. I'm going to use a thermocouple enabled temperature measuring device I have to measure different points along the height of the PEEK insulator to determine where it's best installed. If the hotend goes into runaway, it's going to ***hopefully*** trip the thermal fuse before stuff goes cablooey. It's definitely going to be an experiment. I'll follow up on my experiements in a separate thread.

Edited 2 time(s). Last edit at 01/17/2014 01:35PM by umdpru.

I can not find a thermal fuse that cuts off above 280C, the 240C one is only rated to operate at 200C. Operating it above 200C for extended time damages it.

I do not see thermal fuses being useful at all for hotend use unless you already determined you do not want to exceed 200-240C(if you can find the one rated to sustain 240C).

The largest one I can find is rated to sustain 230C and it triggers at 280C, I can only find it on alibaba/aliexpress. Part number is DF280S.

Edited 1 time(s). Last edit at 01/17/2014 01:36PM by tjb1.

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tjb1
I can not find a thermal fuse that cuts off above 280C, the 240C one is only rated to operate at 200C. Operating it above 200C for extended time damages it.

I do not see thermal fuses being useful at all for hotend use unless you already determined you do not want to exceed 200-240C(if you can find the one rated to sustain 240C).

If your hot end gets hot enough to start trouble then the surrounding components will also get hotter than their normal temperature ranges. The surrounding component temperatures are likely to be a LOT less hot than the hot end itself which is what I am counting on.

For instance, PEEK has a glass transition temperature of 143 C, so you could choose an appropriate thermal fuse and mount it in close contact with a PEEK insulator on a J-Head, for instance, and use the PEEK as the "trip wire" so to say for a run away heater. Your machine will suffer damage, even so, however, it's FAR less likely to cause c a t a s t r o p h i c damage or burn your house down, in my opinion.

Edited 3 time(s). Last edit at 01/17/2014 01:44PM by umdpru.

When I had my near miss and the thermistor pulled out during a print, the temperature obviously dropped below the set point putting full power on the hotend. It got hot enough to melt the peek bit of my jhead and it caused the ball of melted plastic going round with with the head to thermally decompose. There were no flames but clouds of black acrid smoke which filled the living room. Flames would have been next. The dislodged thermistor was tangled up in the ball of molten spaghetti so it did not read as a very low temperature as suggested. Other comments:-

HEATER_0_MINTEMP 5 is on line 100 in my version of Marlin. This is for disabling the heater if the thermistor wiring goes open circuit. i.e. max resistance.

HEATER_O_MAXTEMP 245 is on line 108. This switches the heater off if it fails to control properly and goes overtemp. It is not for thermistor failure. It also stays off until there is a reset. I had problems with this until I tuned the PID settings.

EXTRUDE_MINTEMP 180 is on line 209. This stops the extruder motor unless the temp is above the setting. I have mine set for ABS.

What we want is something else. I don't know enough about the programming language the Arduino uses but I can make a suggestion.

IF the heater is on and IF the hotend temperature drops more than a certain rate over a certain period of time , then it disables the heater.

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dave3d
When I had my near miss and the thermistor pulled out during a print, the temperature obviously dropped below the set point putting full power on the hotend. It got hot enough to melt the peek bit of my jhead and it caused the ball of melted plastic going round with with the head to thermally decompose. There were no flames but clouds of black acrid smoke which filled the living room. Flames would have been next. The dislodged thermistor was tangled up in the ball of molten spaghetti so it did not read as a very low temperature as suggested. Other comments:-

HEATER_0_MINTEMP 5 is on line 100 in my version of Marlin. This is for disabling the heater if the thermistor wiring goes open circuit. i.e. max resistance.

HEATER_O_MAXTEMP 245 is on line 108. This switches the heater off if it fails to control properly and goes overtemp. It is not for thermistor failure. It also stays off until there is a reset. I had problems with this until I tuned the PID settings.

EXTRUDE_MINTEMP 180 is on line 209. This stops the extruder motor unless the temp is above the setting. I have mine set for ABS.

What we want is something else. I don't know enough about the programming language the Arduino uses but I can make a suggestion.

IF the heater is on and IF the hotend temperature drops more than a certain rate over a certain period of time , then it disables the heater.

I've posted a request for something like that in the Repetier section here.

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umdpru

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tjb1
I can not find a thermal fuse that cuts off above 280C, the 240C one is only rated to operate at 200C. Operating it above 200C for extended time damages it.

I do not see thermal fuses being useful at all for hotend use unless you already determined you do not want to exceed 200-240C(if you can find the one rated to sustain 240C).

If your hot end gets hot enough to start trouble then the surrounding components will also get hotter than their normal temperature ranges. The surrounding component temperatures are likely to be a LOT less hot than the hot end itself which is what I am counting on.

For instance, PEEK has a glass transition temperature of 143 C, so you could choose an appropriate thermal fuse and mount it in close contact with a PEEK insulator on a J-Head, for instance, and use the PEEK as the "trip wire" so to say for a run away heater. Your machine will suffer damage, even so, however, it's FAR less likely to cause c a t a s t r o p h i c damage or burn your house down, in my opinion.

But this is of no use to anyone running an all-metal hotend unless they plan on just using PLA. I extrude ABS at temps higher than any thermal fuse can take and even when my thermistor failed on the E3D, the fan shroud (PLA) which is 3mm from the heatblock did not melt or show any deformation but the Kapton on the heatblock turned black and crispy so the thermal fuse would be useless unless it was mounted directly in the heatblock in my case.

What we need has been stated a few times, a firmware watch for temperature swings. I have posted in Repetier to try to get it added to that firmware.

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umdpru

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tjb1
I can not find a thermal fuse that cuts off above 280C, the 240C one is only rated to operate at 200C. Operating it above 200C for extended time damages it.

I do not see thermal fuses being useful at all for hotend use unless you already determined you do not want to exceed 200-240C(if you can find the one rated to sustain 240C).

If your hot end gets hot enough to start trouble then the surrounding components will also get hotter than their normal temperature ranges. The surrounding component temperatures are likely to be a LOT less hot than the hot end itself which is what I am counting on.

For instance, PEEK has a glass transition temperature of 143 C, so you could choose an appropriate thermal fuse and mount it in close contact with a PEEK insulator on a J-Head, for instance, and use the PEEK as the "trip wire" so to say for a run away heater. Your machine will suffer damage, even so, however, it's FAR less likely to cause c a t a s t r o p h i c damage or burn your house down, in my opinion.

I agree with that get it on something that's close to the hot end using infrared thermometer check for the temperature and buy the right fuse . If you have a metal enclosure around the whole printer soon as the fuse trips all power will be cutoff the worst thing that could happen fire would burn itself out inside metal enclosure

Edited 1 time(s). Last edit at 01/17/2014 01:58PM by cnc dick.

We need both actually. A few extra lines of code in the firmware sure, but also a hardware safety device to shutdown the printer in the event of a fire.

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dave3d
We need both actually. A few extra lines of code in the firmware sure, but also a hardware safety device to shutdown the printer in the event of a fire.

I agree we need both and I'm glad people are starting to think about safety

Antslate and I come from the radio control world where we've dealt with safety and fires related to lithium polymer battery charging. Speaking for myself, fire is ALWAYS on my mind. I have a hardwired smoke detector right above my bench where I charge and where my printer now lives. That detector has already caught one small fire nearly immediately and I would recommend to everyone to get one. They are cheap insurance but not a guarantee. They are tool to be used correctly. For instance, they won't do anything if you print and leave the house and "it" hits the fan.

Where do we go to recommend firmware safety improvements? The Marlin Git?

Edited 1 time(s). Last edit at 01/17/2014 02:17PM by umdpru.

An electrical thermal fuse is difficult to implement I think.

When I used to run large steam raising boilers, we just ran plastic air tubing across the front of the boiler that held the gas supply valve open. In the event of a fire the tubing melted and closed the gas valve. Simple.

Only problem I can see applying the principle to a 3d printer is how to pressurise a thin plastic tube to keep an electrical switch open.

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tjb1

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brnrd

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tjb1
I'm pretty sure MINTEMP is just a thermistor initialization check and can not be used during printing because the printer would never start if this is within 5 degrees of extrusion temp. I think the feature you are thinking of is the min extrusion temp which just prevents extrusion and would not shut the printer off.

I can't look at the code now but I'm pretty sure that the firmware would turn off power to the hot end if the reading goes below MINTEMP and above MAXTEMP at anytime. A disconnected thermistor would read as a very low temperature and a shorted thermistor would read a very high temperature. I think Marlin would require you to issue an M command or reset the controller when that happens.

Those are not checked during printing though, I did not receive an error until I tried to restart the print and it went through the checks again.

Were you using Marlin? What did you do exactly? Did the heater to the extruder stay on while printing after you disconnectred/shorted the thermistor leads? The temperature control loop is always running and I see codes there to check if it's within the range mintemp to maxtemp.

Edited 1 time(s). Last edit at 01/17/2014 02:26PM by brnrd.

umdpru: you have just given me an idea. Is it possible to pick up a signal from a smoke detector that can be used to shutdown a printer?

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brnrd

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tjb1

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brnrd

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tjb1
I'm pretty sure MINTEMP is just a thermistor initialization check and can not be used during printing because the printer would never start if this is within 5 degrees of extrusion temp. I think the feature you are thinking of is the min extrusion temp which just prevents extrusion and would not shut the printer off.

I can't look at the code now but I'm pretty sure that the firmware would turn off power to the hot end if the reading goes below MINTEMP and above MAXTEMP at anytime. A disconnected thermistor would read as a very low temperature and a shorted thermistor would read a very high temperature. I think Marlin would require you to issue an M command or reset the controller when that happens.

Those are not checked during printing though, I did not receive an error until I tried to restart the print and it went through the checks again.

Were you using Marlin? What did you do exactly? Did the heater to the extruder stay on while printing after you disconnectred/shorted the thermistor leads? The temperature control loop is always running and I see codes there to check if it's within the range mintemp to maxtemp.

Repetier, printing at 310C, thermistor either failed or shorted to heater block and continued to run full power for 3 minutes before I tried to restart and then it caught the thermistor failure. Maybe the MINTEMP works but the thermistor was still reporting between 170C and 310C randomly.

Yes. You'd have to hack the smoke detector, but it certainly can be done.

---

- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

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dave3d
umdpru: you have just given me an idea. Is it possible to pick up a signal from a smoke detector that can be used to shutdown a printer?

I think that's a great idea.This is what I mean people start throwing ideas around brainstorming is what we used to call it all of a sudden one pops out of thin air

Very easy indeed if you use a smoke detector that's designed to work with an alarm panel, 4 wires, +12 and ground, the other 2 are a normally closed switch that will go open on alarm activation. While I don't know the firmware structure at all yet, it can't be more than a few lines in the right place to check, detect and branch accordingly, and the alarm will be making enough noise to raise the dead at this stage, so the software side of it is relatively academic, unless you're out, you will already be well aware that there is a problem with the printer.

---

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dave3d

HEATER_O_MAXTEMP 245 is on line 108. This switches the heater off if it fails to control properly and goes overtemp. It is not for thermistor failure. It also stays off until there is a reset. I had problems with this until I tuned the PID settings.

/quote]

The maxtemp parameter is also for when the thermistor leads are shorted since a short would read as a very high temperature.

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tjb1

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brnrd

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tjb1

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brnrd

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tjb1
I'm pretty sure MINTEMP is just a thermistor initialization check and can not be used during printing because the printer would never start if this is within 5 degrees of extrusion temp. I think the feature you are thinking of is the min extrusion temp which just prevents extrusion and would not shut the printer off.

I can't look at the code now but I'm pretty sure that the firmware would turn off power to the hot end if the reading goes below MINTEMP and above MAXTEMP at anytime. A disconnected thermistor would read as a very low temperature and a shorted thermistor would read a very high temperature. I think Marlin would require you to issue an M command or reset the controller when that happens.

Those are not checked during printing though, I did not receive an error until I tried to restart the print and it went through the checks again.

Were you using Marlin? What did you do exactly? Did the heater to the extruder stay on while printing after you disconnectred/shorted the thermistor leads? The temperature control loop is always running and I see codes there to check if it's within the range mintemp to maxtemp.

Repetier, printing at 310C, thermistor either failed or shorted to heater block and continued to run full power for 3 minutes before I tried to restart and then it caught the thermistor failure. Maybe the MINTEMP works but the thermistor was still reporting between 170C and 310C randomly.

I don't know about Repetier, but I'm quite sure that it works in Marlin since the checks are done in the temperature control loop.