Does the TAZ have any over heating safety measures?

A forum dedicated to the stock LulzBot TAZ 3D Printer
AverageVeganDude
Posts: 111
Joined: Sat Dec 26, 2015 11:27 pm

Does the TAZ have any over heating safety measures?

Post by AverageVeganDude » Fri Jan 08, 2016 1:03 am

I was curious about the safety of the Taz for doing prints while you step away. Many of the consumer 3d printers today are made my smaller companies (compared to GE etc) and probably don't have the R&D funds to do rigorous testing. A lot of these are hobbiest type equipment not factory grade etc. That being said, what do you guys do for prints that will last way too long for you to sit and watch it?

How safe do you feel these printers are? Like all of you I do live in a wood based home :)

Thanks,
Chris

wmgeorge64
Posts: 410
Joined: Wed May 27, 2015 7:28 pm

Re: Does the TAZ have any over heating safety measures?

Post by wmgeorge64 » Fri Jan 08, 2016 7:31 am

This was discussed on some Forum and I can't remember where. I had an issue when printing with a USB connection where the computer was trying to do a update or something and it lost communication. I came in hours later and the printer had stopped but the heaters were still on!

So I now print from the SD card, make sure my computer wireless is turned off and then if its going to be overnight disconnect the USB cable. The printer now is in a location so if it did overheat the resulting fire would not burn the building down!

Safety wise I think a thermal one time fuse like used in coffee makers, toasters and the like might be one answer. Small about the size of a large diode, and they come in different heat ranges. When that heat range is exceeded they open the circuit. They can carry several amps, and are not expensive, maybe $2 or so. They could be attached near the print head, and wired in series with a power wire to the heater.
ULS Laser . Retired master Electrician in Iowa USA Lots of Hobbies

Sebastian
Posts: 514
Joined: Sun Sep 13, 2015 5:54 am

Re: Does the TAZ have any over heating safety measures?

Post by Sebastian » Fri Jan 08, 2016 8:31 am

We had one thread here where a heater cartridge came out of the heater block, burning down the hot end. I can't find it at the moment, you may search for it..
That said, there is a risk of fire like with every thing that gets very hot. But there is a thermal safety function implemented in the Marlin Firmware that prevents thermal runaway. I have no idea why, but it is disabled in the Lulzbot default configuration :?

You may download the Firmware from lulzbot.com and enable the feature on your own, or you may try the latest Marlin release with my configuration. You can find the link in my signature. In this version, the thermal protection is enabled.

The thermal protection compares the measured values with expected ones. For the case mentioned above where the heater was out of the heater block, the firmware would recognise that it increases the power to the heater, but the measured temperature is droping which is not logic. In this situation, the safety function disables the heaters and prevent any further activity until you power cycle the printer. 8-)

AverageVeganDude
Posts: 111
Joined: Sat Dec 26, 2015 11:27 pm

Re: Does the TAZ have any over heating safety measures?

Post by AverageVeganDude » Fri Jan 08, 2016 8:32 am

Makes sense. Probably involve a few hours of me trying to figure out how to do this but makes sense.

wmgeorge64
Posts: 410
Joined: Wed May 27, 2015 7:28 pm

Re: Does the TAZ have any over heating safety measures?

Post by wmgeorge64 » Fri Jan 08, 2016 9:21 am

So does this....
That said, there is a risk of fire like with every thing that gets very hot. But there is a thermal safety function implemented in the Marlin Firmware that prevents thermal runaway. I have no idea why, but it is disabled in the Lulzbot default configuration :?

Prevent overheating do to a thermistor circuit failure or component failure on the control board? I have seen pictures of burned up 3D printers, once the heater cartridge is out of control it can go high enough to start that roll of plastic burning and its good bye whatever room.

The thermal fuse does not care, if its over the threshold of the fuse it opens and stays open. Yes you should have spares.

We run into the same issues with leaving a laser engraving/cutting machine operating when your out of the room. Not recommended.
ULS Laser . Retired master Electrician in Iowa USA Lots of Hobbies

Sebastian
Posts: 514
Joined: Sun Sep 13, 2015 5:54 am

Re: Does the TAZ have any over heating safety measures?

Post by Sebastian » Fri Jan 08, 2016 9:33 am

wmgeorge64 wrote:Prevent overheating do to a thermistor circuit failure or component failure on the control board? I have seen pictures of burned up 3D printers, once the heater cartridge is out of control it can go high enough to start that roll of plastic burning and its good bye whatever room.
First, I'm sure there will be special combinations of events where this feature will not prevent a burn down. But they may be very unlikely..
Some situations where the thermal protection will safe your printer:
.) Circuit failure: The heater gets full power instead of PWM. In this case, the measured temperature rises while Marlin reduces the power => shutdown.
.) Temp. Sensor failure: The measured temperature will read very high or verly low and is not changing with increasing or decreasing heater power => shutdown.
.) Heater out of heater block: As stated above, Marlin would increas the power to the heater, but measured temperature is not responding as expected => shutdown.
.) Bad heater, loose contact (mechanical or electric): If the temperature during heat up period is not rising a minimum of some °C in a given amount of time, it will also shutdown the printer.

I consider it to be quite safe. Much better than with disabled feature at least :lol:

wmgeorge64
Posts: 410
Joined: Wed May 27, 2015 7:28 pm

Re: Does the TAZ have any over heating safety measures?

Post by wmgeorge64 » Fri Jan 08, 2016 9:47 am

It would be an interesting feature to have working and I wonder why its not done?? :(
ULS Laser . Retired master Electrician in Iowa USA Lots of Hobbies

Sebastian
Posts: 514
Joined: Sun Sep 13, 2015 5:54 am

Re: Does the TAZ have any over heating safety measures?

Post by Sebastian » Fri Jan 08, 2016 9:57 am

wmgeorge64 wrote:It would be an interesting feature to have working and I wonder why its not done?? :(
Maybe I'm missing what you are meaning, but it is done. Marlin can do it, but I was wrong before: It's not enabled in the original firmware because it was not implemented at that time :oops:
In my RC2 version, it's enabled. Here is the description from configuration.h, you can find more options about preheat-phase in the advanced config.h:

//===========================================================================
//======================== Thermal Runaway Protection =======================
//===========================================================================

/**
* Thermal Runaway Protection protects your printer from damage and fire if a
* thermistor falls out or temperature sensors fail in any way.
*
* The issue: If a thermistor falls out or a temperature sensor fails,
* Marlin can no longer sense the actual temperature. Since a disconnected
* thermistor reads as a low temperature, the firmware will keep the heater on.
*
* The solution: Once the temperature reaches the target, start observing.
* If the temperature stays too far below the target (hysteresis) for too long,
* the firmware will halt as a safety precaution.
*/

#define THERMAL_PROTECTION_HOTENDS // Enable thermal protection for all extruders
#define THERMAL_PROTECTION_BED // Enable thermal protection for the heated bed

ttabbal
Posts: 298
Joined: Wed Nov 11, 2015 4:20 pm

Re: Does the TAZ have any over heating safety measures?

Post by ttabbal » Fri Jan 08, 2016 10:22 am

Interesting topic. I was wondering about similar issues the other day. I left a print running and had to go out for a while. I use Octoprint, so I can VPN to my network and check on it once in a while. It's not as nice as an automated shutdown built in, but at least the standalone machine (raspberry pi2) doesn't have auto-updates and other software to crash the system. As I am on a mini, no SD to print from, but IMO this is the next best thing.

I would like to build a version with the thermal protection enabled. Is there any reason a mini couldn't build from the Marlin tree? The source on the lulzbot site is an Arduino project, easy enough to work with.

Edit: Found the repo, https://code.alephobjects.com/diffusion/MARLIN/

Guess I need to do some reading.

Sebastian
Posts: 514
Joined: Sun Sep 13, 2015 5:54 am

Re: Does the TAZ have any over heating safety measures?

Post by Sebastian » Fri Jan 08, 2016 10:53 am

You might ask rjhubott in his thread if he wants to share his configuration of Marlin RC3. He has done the work you want to do two days ago ;)
Would be nice to have also a community-"developed" FW version for the Mini!

Post Reply