Does the TAZ have any over heating safety measures?

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 :slight_smile:


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.

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 :confused:

You may download the Firmware from 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. :sunglasses:

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

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 :confused:

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.

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 :laughing:

It would be an interesting feature to have working and I wonder why its not done?? :frowning:

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 :blush:
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

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,

Guess I need to do some reading.

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 :wink:
Would be nice to have also a community-“developed” FW version for the Mini!

It would be an interesting feature to have working and I wonder why its not done?? :frowning:

I was wondering why it was not implemented, its kind of a common sense thing.

I have a Raspberry Pi and the webcam just have not got it done yet. So many things to do, even if your retired :slight_smile: and still learning .

ttabbal Can you use your Pi setup to manually move the printer axis and prime the extruder like I do now with my PC?

I am not him, but to answer. Yes I do it quite often with Octoprint. :sunglasses:

Thanks for the tip! I posted over there, hopefully we can get something going for the Mini.

And yes, there are controls in Octoprint for the movement and temperature settings. In some ways, they aren’t as nice as Cura/Simplify3D, but they get the job done.

Well my plan is to use Simplify 3D for the slicer and Save the gcode to a SD. So I am assuming the Octoprint runs on the SBPi and the screen you have connected to it, allows you to control the machine interface. I’m sure I have missed something but trying to juggle a few projects around to get the time for this. Thanks again for the postings.

The worst case is when the board fails and puts constant power to the hotend. No configurations will help this and it often ends in fire. Over on the RepRap forums there is a thread dedicated to safety and you can read some of the horrors that have gone wrong including fire that almost burned down the owners houses.

It can happen but is still unlikely. Best thing to do is prepare for a worst case scenario just in case. Always have a fire extinguisher handy of ample size (not one of those kitchen ones but at least a 5lb one). Of course one of the big no-no’s that everybody does is that you should not leave your printer unattended while printing. Keep flammables away from it as best you can (curtains and such).

Some people are going to the extreme of hanging self activating fire extinguishers above the printer or having a second temperature sensor on the hotend with a power cutoff relay so if it goes above say 300c it cuts the AC power. A fire proof (or resistant) enclosure is another good idea.

You really don’t need to be afraid of your printer, just aware of what may happen and take the measures that make you feel best.

I’ve gone the route of home automation to implement safeguards with the printer. A motion sensor under the bed senses movement, power to the printer is shutoff after a 20min delay when no motion is sensed. WeMo has a quick and dirty motion sensor & plug combo… at least last time I checked.

I use a Smartthings Hub with Zigbee sensors and plug. It allows for integration of a First Alert Smoke/Fire detector… so if smoke/fire is detected, the plug shuts off. The printer safe guard is in addition to the home monitoring and alerting through the home automation.

The solution works well. Utilizing the remote printing through Octoprint, I’ve only baby sat two or three prints in the time I’ve owned my TAZ5.

I don’t have a screen connected to the pi. It’s possible to do, but I have my smartphone with me most of the time and can control it over the network that way. I also have computers in the room.

So my workflow is to slice and save the gcode on the computer using Simplify3D, or Cura. I have a browser open to the Octoprint page. Bring that up, then the file browser already open to the gcode directory. Drag the gcode to the left side of the webpage and it automatically uploads to octoprint which saves it on the SD card that’s already in the pi. Then click print and it goes.

If you drop the file on the right side, it will save to the printer’s SD card. At least that’s what it says, my Mini doesn’t have a slot so I don’t know. But since I have octoprint running already, I figure it doesn’t hurt anything to let it feed the gcode to the printer.

It also has the Webcam feed which is handy for checking on the print in progress. I use the camera module the pi people make and a printed mount. I added some LED lighting so I can turn the room lights off and still see the image. That same page has controls for the X/Y/Z steppers and extruder. The temperature gets its own tab.

Excellent posts on using the Raspberry Pi and fire safety.

So did most of the fires start because of a software glitch and extruder heater or did the fire start elsewhere on the machine?

ttabbal Thanks for the detailed write up for printing remotely.

The most common 3d printer fire causes are:

  1. the heater core fell out of the heater block, the thermistor tried to heat up the block and caused the heater core to basically melt down and combust.
  2. The nozzle dug into the part it was printing, got it wrapped up around the hot end, and then eventually the plastic combusts
  3. The controller board fails in a manner that causes power feed to the hot end constantly with no imput from the thermistor, causing it to melt down in the nozzle and combust. RAMPS and RAMBO boards don’t seem to be as prone to that.
  4. The power supply itself catches on fire due to being a cheap knockoff, or wired incorrectly

Sebastian’s exactly right. The feature isn’t disabled on the TAZ, the thermal runaway wasn’t even implemented until it came out around the time we were working on the Mini and TAZ 5. We implemented it on the Mini but had to disable it for release as it had been throwing false positives frequently.

Anyway, we’ve continued to work on the feature and have a pretty stable setup in the TAZ 6 development firmware: There are also some other neat features we’re testing like the ability to resume printing after shutting off the printer and micron level control of the first layer height through the LCD :slight_smile: .

On a side note, we’ve always put a lot of effort into making our hotends as safe as possible. Neither the Budaschnozzle or the AO-Hexagon rely on tape, rubber or glue to secure the heater and thermistor in place. The thru-hole design of the budaschnozzle and the retention plate on the side of the AO-Hexagon make it so that if the thermistor or HC are pulled out of the hotend they’ll break at the retention plate and cause printer shutdown. In fact out of the millions of print hours in our cluster and the thousands of Lulzbots out there in the world, thermal runaway has never happened on one of our machines in stock configuration. The only thermal runaway we’ve heard of was caused by a non-stock hotend having its thermistor pulled out of the kapton tape holding it in place. Moral of the story: We try to make our products as safe as possible, but please be extremely careful if you decide to modify or replace the hotend.