Hot end catastrophic failure

Discussion in 'OpenBeam Kossel Reprap and OpenBeam Kossel Pro' started by Abc123, Aug 16, 2015.

  1. Abc123

    Abc123 New Member

    Hi all,

    We assembled our printer, hooked it up, and tested the motors. Then we tested the hot end... We clicked preheat, and once it reached 80 degrees C, we clicked 'off'. We noticed smoke coming from the hot end, so we looked back at the software to find the temperature had climbed to 500 C+ [preheat temperature was supposed to be 230 C]. We clicked 'off' multiple times to no avail, so we unplugged the printer, but the casing for the hot end had already melted and the heating element was glowing red hot. Does anyone have thoughts on why this may have occurred? We ordered another Jhead, but want to be sure this doesn't happen again.
  2. protoserge

    protoserge Member

    I've noticed a few times during G29 that the temperature overshoots by a significant margin. I am wary of the Brainwave board as it looks at first glance that it does not have a watchdog or other monitoring of the temperature while it is doing the G29. I could be wrong of course.

    Were you doing anything while testing the motors?
    Last edited: Aug 17, 2015
  3. AndyG

    AndyG Member

    Are there any Marlin boards that have a watchdog built in?

    If you were using an original Jhead was it potted from the Openbeam guys? Was it reading room temp when you first turned the printer on? Just wondering if the constants were set correctly in the firmware.

    It sounds like you were seeing temp rises so at least you're getting some feedback.

    I think Protoserge is on the right track - either the brainwave had an issue while the hot end was heating or it was tied up doing something else at the time like running a G29 or something.
  4. chadman

    chadman Member

    I concur with the G29 and heating issue. When getting mine running, I observed behavior that led me to believe temperature wasn't being monitored during G29 as well. I'm intentional about not asking the Brainwave to do both simultaneously. That was quite a while ago, so my recollection of specifics is fuzzy.
  5. Abc123

    Abc123 New Member

    I apologize but what is G29? We weren't testing the motors as we were preheating, we did them separately. The JHead was prepotted from openbeam. I searched the forums previously and found that others had problems with certain tasks being interrupted during heating, but since I was getting a temperature reading I wasn't really entertaining that possibility.
  6. David Boyd

    David Boyd Active Member

    So G29 is the auto-bed level probing command. It is long running and some early versions of firmware did not properly monitor temperature while that command was running.
    However, it sounds from your description this was something else.
    So some questions to make sure we understand the exact sequence:

    1. What host control program are you using? (Mattercontrol, RepetierHost, ????)?
    2. You powered on the printer and connected?
    3. What did the hot end temp read when you connected (before doing anything)?
    4. You tested the motors and they worked?
    5. You turned on the hotend with a target of 230C via the host control program?
    6. When the hotend reached 80C you turned it off with the host control program?
    7. The hotend never turned off and a few minutes later you had smoke and melted plastic? The hotend read 500C?

    Is that sequence correct?

    So the PEEK portion of the J-head is toast. Is the nozzle, heater block end with the cartridge and thermistor still in tact?

    If so we should try to repeat the problem.
    Couple of thoughts: Early versions of the firmware did not have thermal runaway protection enabled. However, I believe that every version of Marlin for the KP has a max temp that shuts off the entire printer. Most likely I am thinking that something in the MOSFET that controls power to the hot end shorted into an always on position. Very rare condition but it could happen.

    This is why it would be good to see if the problem can be repeated (obviously killing power before extreme temps).
  7. Abc123

    Abc123 New Member

    1. matter control. We initially connected an outdated version in an attempt to use an older pc, but this did not work, could this have had an effect?
    3. It was reading around 23c when we first connected (seemed accurate).

    The rest of the sequence is correct and yes to all questions. We have an IR thermometer so we can get a faster reading this time, and I agree that testing again is a good idea. Will do this and comment afterwards, though more input is obviously welcome!
  8. AndyG

    AndyG Member

    I remember reading about some early batches of heating elements having less than ideal resistance and people were reporting some wild run aways with temp before stabilizing. I wonder if it was a combination of a few things going wrong?

    1 - heating element on the very wrong side of resistance
    2 - un-calibrated PID heating loop with older firmware which wasn't current limited.
    3 - something with software causing a pause of enough time where this ran away?

    Just throwing some ideas of there of things to keep an eye on.

    Might also want to switch over to a k-head if you can - at least for thermal runaways you'll have a bit more wiggle room. At 500C I'm not sure there's much you could do but catch it at 300 you can probably save your hot end.
    Abc123 likes this.
  9. Abc123

    Abc123 New Member

    Ok so here's an update. We plug the unit in and it immediately begins heating the element, I assume this should not be the case. We can connect the software, but the runaway heating problem persists, with the software reading temperatures of 700C before we flip the switch. Thoughts?
  10. David Boyd

    David Boyd Active Member

    Bad controller board or bad wiring.
  11. protoserge

    protoserge Member

    I would think that a failed MOSFET or a short is the cause. Look at the board and see if you can see any obvious shorts on the board itself (maybe a wire is loose under your print bed). Observe everything first, then pull it out and test continuity across the pins and reference the spec sheets for the MOSFET and work back toward the microcontroller. I don't have the Brainwave Pro schematic handy, but it would help with troubleshooting.
  12. Abc123

    Abc123 New Member

    So obviously it has been a while since this post and I hate to revive it, but I had put the printer into storage for a while as troubleshooting it was taking too long and seemed completely fruitless. I recently had some free time, so I put it on my desk to get back to trying to figure this out. I can't find a spec sheet for the MOSFET, do you think the short could be in the end effector? I have been testing continuity, but without knowing what should be connected to what, I'm at a bit of a loss. I updated the firmware just in case, and the issue persists, so I know that's not the issue. I'm tempted to buy a new end effector and a new control board from mattercontrol, because I'm not sure I'll be effective at troubleshooting otherwise. Any ideas on what else I can do before I resort to that?
  13. protoserge

    protoserge Member

    I'd get a new end effector board and upgrade to a Smoothieboard (after swapping the end effector board first and trying with the Brainwave) if I was in the same situation.
  14. Steve Heer

    Steve Heer Active Member

    You might want to enable the thermal runaway in the configuration.h file so the hotend will shut down at a high but safe temp. I know that won't solve the issue of why the heater turns on when the unit is powered up but it will save your hotend from meltdown.
    Here are the settings as I have them configured:

    */
    // If you want to enable this feature for all your extruder heaters,
    // uncomment the 2 defines below:

    // Parameters for all extruder heaters
    #define THERMAL_RUNAWAY_PROTECTION_PERIOD 40 //in seconds
    #define THERMAL_RUNAWAY_PROTECTION_HYSTERESIS 4 // in degree Celsius

    // If you want to enable this feature for your bed heater,
    // uncomment the 2 defines below:

    // Parameters for the bed heater
    #define THERMAL_RUNAWAY_PROTECTION_BED_PERIOD 20 //in seconds
    #define THERMAL_RUNAWAY_PROTECTION_BED_HYSTERESIS 2 // in degree Celsius

    Have you checked the resistance on your heater and thermistor? Heater should be somewhere close to 24-ohms and the thermistor close to 100k-ohms at room temperature.

    You might want to submit a trouble ticket to Mike Ziomkowski since this appears to be a bad controller.
    samspade4321 likes this.
  15. Abc123

    Abc123 New Member

    I don't know who that is. Will google and do that.

    Edit: Derp, I know who mike is. Sending, thanks for the tip.
    Last edited: Jun 18, 2016
  16. Abc123

    Abc123 New Member

    Not sure how to send him a ticket. I used the contact form on this site but haven't recieved a response. Any ideas how to get a hold of him?
  17. Steve Heer

    Steve Heer Active Member

  18. Khom Kaowthumrong

    Khom Kaowthumrong New Member

    I know it's been a while. Abc123, did you get this resolved by any chance? I am running into the same problem now. I think I have isolated this down to the controller board. Pins 1 & 2 of the effector give a constant 23.8V when turned on. Is this what you were seeing on your system also?
  19. Abc123

    Abc123 New Member

    I never got it working. It's still sitting decoratively in my living room. I'll turn it on tomorrow or so and see if I also am getting the same voltage from those pins.
  20. Matt

    Matt New Member

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