Suddenly unable to hold temepratures (and severe damage has possibly occured as a result)

Discussion in 'E3D-v6 and Lite6' started by Patrick Bentley, Dec 30, 2017.

  1. Patrick Bentley

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    A little under a year ago I upgraded my QU-BD TwoUp with a Lite6 and was extremely pleased with the quality of the extruder and the results it was giving. I didn't have any problems with it at all until about a month ago when all of a sudden it started having issues with maintaining temperatures.
    As you can see in the images I've attached, the temperature was jumping all over the place really drastically and it was a pretty serious issue, with temperature readings as much as plus or minus 40 degrees from what it was set to be (with readings as high as 270 at times). I assumed this simply meant my thermistor was the issue, but all my connections seemed to be secure and I didn't know of any way to actually test if it was going bad for some reason.The other really weird aspect about this issue (and part of why I didn't think the thermistor was necessarily the cause) was that it was extremely inconsistent; sometimes it would hold temperature fine until it actually started printing and only then would it go crazy, other times it would hold temperature fine up until a certain temperature (as seen in image 3), and so on. For the most part however, the average temperature would be more or less where I needed it to be and the crazy readings would often work themselves out, so I foolishly kept printing and just wrote it off as a weird bug with the recordings or something.
    This worked out fine with the exception of a few prints here and there that would cancel because the temperature was reading too high and causing an error, until earlier this week when I noticed the smell of the plastic burning as it preheated. Just putting my finger near the hotend was enough for me to tell that it was way overheating, so I immediately killed the power and let it cool. After a little bit I cautiously booted things back up and hoped that that was just a fluke, but after just a minute I could tell the same thing was happening. Before I could shut things down, there was a popping noise, a spark, and a lot of smoke from the hotend and I could tell it was really really hot. I haven't touched any of it since or tried to asses the damage because I'm a little scared to do so. I'm assuming the PTFE barrel is melted and I wouldn't be surprised if I shorted something on my board too.
    I'm not entirely sure where to go from here. What do you guys think went wrong initially, and what do you think went wrong this last time? How much do you think is broken and will need replaced? Is this something I could try and still fix or will I need to just get new things? Is there any chance that this is all the result of something failing on the hotend and I will be able to get replacements from E3D, or is it entirely my fault and I'm going to have to buy new things myself? Thank you in advance for any help or suggestions you might have, I really appreciate it. Please just let me know if there's any more information I could provide to help or anything else. Thank you! Capture1.PNG Capture3.PNG Capture4.PNG
     
  2. Old_Tafr

    Old_Tafr Well-Known Member

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    If not fried already can you check the resistance of your thermistor? Type/model/ part number/maker/supplier I assume you have to get what its characteristics are.

    Have you a meter? and do you know how to use it to measure resistance? Digital is possibly better than analogue but either would do.

    If still intact can you check the wiring for insulation and continuity?

    Can you mention what controller you have?

    Is your controller susceptible to static and do you take suitable anti-static precautions?
     
  3. Patrick Bentley

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    Thank you very much for the quick response! I used my multimeter to measure the resistance of the thermistor at room temperature and got 148 Kohm. From what I can find online about the Lite6, it's supposed to have a resistance of 100 Kohm. I don't fully understand resistors, but if I'm not mistaken I think this variance is consistent with the fact that my recorded temperatures were usually lower than what it was set to but the actual temperatures were often higher than what it was set to (based on the smell of plastic and the heat I could feel coming off the hotend). I don't really know what to do with this information or what it means in terms of what went wrong. I also checked the length of the thermistor wire and did not find any issues with the insulation or a discontinuity.
    The controller I have is the Printrboard (the red model). I don't know of it being especially susceptible to static, although it is unprotected and just out in the open so that likely doesn't help. The only anti-static precautions I take are grounding myself before I do any work on the board, but if I'm just starting a print and not actually touching the board I don't do anything. I don't know if this is significant to the static, but I have the controller mounted to a piece of MDF with nylon spacers between it and the screws. Thanks again for your help!
     
    #3 Patrick Bentley, Dec 31, 2017
    Last edited: Dec 31, 2017
  4. dc42

    dc42 Well-Known Member

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    Have you checked that there is no possibility that the thermistor wires are shorting against the hot end metalwork? If your V6 is the older type using the wire ended thermistor instead of the more recent cartridge thermistor, such shorts happen easily. If you decide to try replacing the thermistor, I recommend that you buy the new heater block and cartridge thermistor.
     
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  5. Patrick Bentley

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    I do have the new cartridge thermistor and when I checked, it did not appear that there was any exposed wiring touching anything else that could have caused a short. While I was doing this, I decided to go ahead and just remove the whole cartridge to inspect that while I was at it. I don't know if this is unusual or if it even necessarily means anything bad, but the cartridge appeared "burnt" and had a thick coat of black around it that came off as kind of a charred powder. I assume this is just a consequence of the heater block overheating way too much, but I thought it was interesting and possibly helpful information.
    As far as replacing the thermistor, is this all you think I would need to do? Or do you think I've done more internal damage along the way and would need to replace the whole hotend? Is there any chance I wouldn't have to buy everything and could get replacements sent? Does the fact that the thermistor read nearly 50 Kohm over what it was supposed to imply that it was a faulty thermistor or is that simply a result of me somehow misusing something? Thank you, I really appreciate all the help!
    [​IMG]
     
  6. dc42

    dc42 Well-Known Member

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    A reading of 248K would be correct at about 17C temperature.

    From the graph, it looks to me that the temperature is reading intermittently below actual, but probably only when the heater starts to cut out. This suggest to me that there is leakage between the negative side of the hot end heater and the thermistor. It's not uncommon for cartridge heaters to develop a short or leak between the element and the case, but I've not heard of that happening to cartridge thermistors before.

    I'm not an expert on E3D hot ends, but in your position I would replace the heater cartridge and thermistor. I would also get a new heat break in case the existing one is blocked.
     
  7. Patrick Bentley

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    Alright, thank you, that makes sense. You suggest replacing the heat break, but since I have a Lite6 (only the v6 comes with a heat break) would I be okay just replacing the PTFE liner? As I understand it, replacing this would fix any possible blockage issues.
     
  8. dc42

    dc42 Well-Known Member

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    I haven't used the Lite6 but I guess you should replace the PTFE liner if it looks at all discoloured or misshapen.
     

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