Re: Yes, 3D printers can go on fire. January 17, 2014 07:54AM |
Registered: 11 years ago Posts: 115 |
Re: Yes, 3D printers can go on fire. January 17, 2014 08:21AM |
Registered: 11 years ago Posts: 474 |
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 stripQuote
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.
Re: Yes, 3D printers can go on fire. January 17, 2014 09:21AM |
Registered: 10 years ago Posts: 172 |
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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.
Re: Yes, 3D printers can go on fire. January 17, 2014 09:27AM |
Registered: 11 years ago Posts: 160 |
Re: Yes, 3D printers can go on fire. January 17, 2014 09:51AM |
Registered: 11 years ago Posts: 553 |
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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.
Re: Yes, 3D printers can go on fire. January 17, 2014 09:56AM |
Registered: 13 years ago Posts: 1,780 |
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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.
Re: Yes, 3D printers can go on fire. January 17, 2014 11:05AM |
Registered: 11 years ago Posts: 553 |
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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.
Re: Yes, 3D printers can go on fire. January 17, 2014 11:13AM |
Registered: 10 years ago Posts: 172 |
Re: Yes, 3D printers can go on fire. January 17, 2014 11:59AM |
Registered: 13 years ago Posts: 1,236 |
Re: Yes, 3D printers can go on fire. January 17, 2014 12:03PM |
Registered: 10 years ago Posts: 172 |
Re: Yes, 3D printers can go on fire. January 17, 2014 12:51PM |
Registered: 11 years ago Posts: 553 |
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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.
Re: Yes, 3D printers can go on fire. January 17, 2014 01:14PM |
Registered: 13 years ago Posts: 1,797 |
Re: Yes, 3D printers can go on fire. January 17, 2014 01:26PM |
Registered: 10 years ago Posts: 172 |
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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.
Re: Yes, 3D printers can go on fire. January 17, 2014 01:34PM |
Registered: 11 years ago Posts: 553 |
Re: Yes, 3D printers can go on fire. January 17, 2014 01:43PM |
Registered: 10 years ago Posts: 172 |
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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).
Re: Yes, 3D printers can go on fire. January 17, 2014 01:46PM |
Registered: 11 years ago Posts: 329 |
Re: Yes, 3D printers can go on fire. January 17, 2014 01:55PM |
Registered: 11 years ago Posts: 553 |
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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.
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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.
Re: Yes, 3D printers can go on fire. January 17, 2014 01:55PM |
Registered: 11 years ago Posts: 474 |
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 enclosureQuote
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.
Re: Yes, 3D printers can go on fire. January 17, 2014 02:00PM |
Registered: 11 years ago Posts: 329 |
Re: Yes, 3D printers can go on fire. January 17, 2014 02:03PM |
Registered: 11 years ago Posts: 474 |
Re: Yes, 3D printers can go on fire. January 17, 2014 02:16PM |
Registered: 10 years ago Posts: 172 |
Re: Yes, 3D printers can go on fire. January 17, 2014 02:21PM |
Registered: 11 years ago Posts: 329 |
Re: Yes, 3D printers can go on fire. January 17, 2014 02:26PM |
Registered: 13 years ago Posts: 1,780 |
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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.
Re: Yes, 3D printers can go on fire. January 17, 2014 02:27PM |
Registered: 11 years ago Posts: 329 |
Re: Yes, 3D printers can go on fire. January 17, 2014 02:40PM |
Registered: 11 years ago Posts: 553 |
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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.
Re: Yes, 3D printers can go on fire. January 17, 2014 03:09PM |
Registered: 12 years ago Posts: 809 |
Re: Yes, 3D printers can go on fire. January 17, 2014 03:47PM |
Registered: 11 years ago Posts: 474 |
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 airQuote
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?
Re: Yes, 3D printers can go on fire. January 17, 2014 04:26PM |
Registered: 12 years ago Posts: 40 |
Re: Yes, 3D printers can go on fire. January 17, 2014 04:52PM |
Registered: 13 years ago Posts: 1,780 |
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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.
Re: Yes, 3D printers can go on fire. January 17, 2014 04:54PM |
Registered: 13 years ago Posts: 1,780 |
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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.