E3D V6 hot end temperature

Discussion in 'E3D-v6 and Lite6' started by Jason_WI, Aug 25, 2014.

  1. Jason_WI

    Jason_WI Member

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    I'm having jamming issues with PLA. Seems like it will print for a few layers then quit. I have the temperature set to 180C and am using thermistor 5 setting in Marlin. I thought maybe my cooling fan was causing issues with the nozzle temperature. I added a T type thermocouple to the heat block and one to the nozzle body on one of the hex faces. What I recorded was disturbing. The nozzle temperature is some 50C cooler than the heater block. I believe this is the cause of the jamming.

    I have attached a plot of the data. The 25mm test cube failed on this print with severe streaking and air print. The temperature transfer from the heat block to the nozzle is poor. Not sure of it has to to with the aluminum heat block mass or the fact its is threaded and not completely machined as one assembly. I have this assembled per the instructions online.

    I wonder if using artic silver on the threads of the nozzle would help with the heat transfer?

    Jason

    Edit:
    Added 200C plot
     

    Attached Files:

  2. Fourtree

    Fourtree Member

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    Thank you for posting this information. I had tested with a thermocouple at the nozzle and recorded roughly 40° off what the thermistor was reporting. I was about to embark on further tests to determine if the thermistor was wrongly calibrated.

    If it's a heat conduction issue I am not sure what to do. Artic Silver is not listed as capable of the tempuratues I hope to use.
     
  3. elmoret

    elmoret Administrator

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    Fourtree - were you measuring the outside of the nozzle? Of course it will be cooler (significantly so) than the heat block. I'm not sure why this came as a surprise?
     
  4. Fourtree

    Fourtree Member

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    Here are some details on the observed issue.

    I used a heat probe and measured the tempurature directly below the heater capsule and left the probe in place for five minutes to ensure the probe was at equilibrium with the heat block. This measured 30°C below the thermistor. The same test at the tip of the nozzle demonstrated 40°C below the desired temperature. The tempurature of molten PLA at the nozzle was measured as well and confirmed to be the same as the nozzle itself.

    In addition to measured information I gathered empirical data based on calibration object print tests of objects known to print properly using a j-head with an epoc thermistor on the same hardware and with firmware only differing in the configuration settings requested in the v6 assembly guide. The j-head only exhibited the expected 5° variance from the tempurature reported.

    The test prints all failed in quality until the print tempurature was raised by 35°C and then all objects printed above previous standards

    The long leads provided in the kit may be a factor and I will be repeating my tests after trimming to the minimal suitable length for the printer.

    @elmoret, as a personal aside:
    Do not take an accusatory tone with implied assumptions of foolishness with me. Do not comment on my expressed emotions in a condesending tone. If you are interested in more detailed information from me please simply ask for it. There is no need to attempt to cajole me into a response.
     
  5. elmoret

    elmoret Administrator

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    Fourtree: No condescending tone intended - was genuinely surprised that you think a probe on the surface of a heat block would report the same temperature as a sensor embedded in the block. Part of the sensor on the outside is cooled by ambient air, so it is not going to report as high as the sensor in the block. For example, the Solidoodle hotend measures with a thermistor on the outside of the nozzle, and prints ABS at "195C". Hotends that put the sensor in the block need 230C+ to print ABS. The E3D puts the thermistor in a differently location relative to the heater as compared to the J-head, so these measurements are not meaningful to compare against each other. Additionally each time you stick the probe up against the surface, you're bound to get a bit different thermal coupling - so measurements aren't repeatable or meaningful either. The only thing that would be meaningful is to put a probe all the way down the barrel of the hotend, stopping at the level of the heat block. This is what E3D recommends if you want to further calibrate things.

    To me this is all straightforward (hence my surprise), but I guess not to everyone. No reason to get offended.

    The length of the thermistor leads is definitely not a contributing factor. The total resistance of that cable is less than an ohm, and the resistance of the Semitec 104GT2 is a couple hundred ohms in that temperature range - so less than a degree of inaccuracy stems from any cable losses. There's much more inaccuracy in the control board's balancing resistor.

    If you get good prints at 30C higher temps, then why not just print at 30C higher temps? Not sure I see the problem here...?
     
  6. deltaford

    deltaford New Member

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    I was having jamming issues with PLA and my theory after a lot of testing was also that it might be caused by to low nozzle temperature. As a simple test and workaround I made an aluminium nozzle hood (from a $2 drawer handle) to maximize heat transfer from the heating block to the nozzle. Haven't had a jam since.
     

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