Hot end hovering below target and never reaching

Discussion in 'E3D-v6 and Lite6' started by acousticnewton, Mar 27, 2015.

  1. acousticnewton

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    I just switched out to the V6 volcano hotend a little over a week ago. I'm running modified marlin on a Gigabot printer.

    24V 3mm direct.

    First I changed the thermistor type in the firmware to:

    104GT2 thermistor
    #define TEMP_SENSOR_0 5

    Ran PID autotune with these results first

    KP 71.10
    Ki 13.56
    Kd 93.18

    I started having problems with the controller throwing max temp and thermal runaway errors, even though I'm sure the thermistor is secured properly etc.

    In the firmware I changed a couple things that fixed that:

    #define HEATER_0_MAXTEMP 290 //originally 250

    #define THERMAL_RUNAWAY_PROTECTION_PERIOD 60 //in seconds originally 40

    #define THERMAL_RUNAWAY_PROTECTION_HYSTERESIS 10 // in degree Celsius oringinally 4

    These changes seemed to avoid the max temp and thermal runaway errors, but now on to my main problem.

    When I manually set the temp to say 230, it runs fine and quickly, but when I start a print the temp comes up to about 15 degrees under the target temp and then just hovers there without ever reaching the target temp.

    I've run PID autotune a few times since then here are my latest results

    M303 S225 C10

    Results:

    Recv: Kp: 13.75
    Recv: Ki: 2.68
    Recv: Kd: 17.66

    M301 P13.75 I2.68 D17.66
    M500


    No matter what I do, the temperature still just hovers under target and never reaches it. Sometimes if I go into the Vika control box while its trying to print I can force it somehow, by randomly changing some PID values and then it seems to work.

    Any idea what I can do to avoid having this happen? Gigabot support has not used your product yet so are clueless on what to do.

    Thanks

    I should also mention that I put together an enclosure for the machine and the heated bed is running at around 80C for these prints.
     
  2. elmoret

    elmoret Administrator

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    Are you saying the hotend reaches 230C if set manually?

    If so, it's not a hotend problem, it's a software problem.
     
  3. AndersE

    AndersE Active Member

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    Do you print with cooling on? If PID is calibrated without fan on, then you will have problems reaching temp when the fan is running.
    I always PID calibrate with fan at 50% on atleast ( i almost never run coolingfan more than 50%)..
     
  4. acousticnewton

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    Yeah I was sure it's a software/firmware problem. I seem to have reached a solution. I ran a PID autotune and increased the Ki value by 50%. Based on the info here: http://reprap.org/wiki/PID_Tuning

    It's coming to target consistently now, I'll update with any further tuning that helps out.
     
  5. AndersE

    AndersE Active Member

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    You will also have problems reaching temps is your heater is too weak.
    Check what heatercartridge you have.
    I just found out my heating problems were because i got a 25w heater in my v6 kit. GAHH..
    When i switched to 40w all problems gone.
     
  6. elmoret

    elmoret Administrator

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    No, like he said his problems were due to having the wrong PID gains.
     
  7. malamaker

    malamaker New Member

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    It could be the PID gains but I'm not convinced totally. The new heaters that are being shipped with the hotends are different (assuming lower wattage). I have 2 machines now with these new heaters and the previously tuned PID settings kinda work but kinda don't. When the heater starts heating it reaches 230c and then just hovers there for about 10 minutes before it ramps back up to the desired temp (245c). I have run PID autotune with the same outcome of the hovering at 230c for 10 minutes and then heat up the rest of the way. I also have done some research on what each value does in the PID settings and have modified to yield faster heat up time with still the same results. If e3D has some example reprap marlin PID settings they can provide for these new heaters that would be great. I'm a little worried because i have 13 more machines that will be getting these heaters and I see the frustration I am feeling with experience in 3DP'ing, the others getting these heater are probably going to be as or more frustrated. Please advise.
     
  8. elmoret

    elmoret Administrator

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    It is 100% PID gains. The 25 watt heaters can achieve 300C+ on a Volcano hotend no less.

    Of course you cannot use the same gains for a 40w heater with a 25w heater, you'll have to retune... but 25w is still more than enough. I average about 14 watts when printing at 250C.
     
  9. ktoth

    ktoth Member

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    This is consistant with the problem I'm having... I can get the hot end up to 245 when running PID autotune. but when I actually try to preheat it tops out at 230. I've tried increasing the PID MAX integral gain value to 235 from 205 but no change... any other suggestions?
     
  10. Mike Kelly

    Mike Kelly Volunteer

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    Why not change the max gain to 255?
     
  11. Mike DiPirro

    Mike DiPirro New Member

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    I see this is an old thread, but I am having the same issue. PID tunes fine at 235 degrees on BigBox with dual v6 hotend, but if I manually set the head temperature to 235 degrees the extruder stabilizes at 220 to 225 degrees (Octoprint or on LCD = same result). The attached screenshot shows dual head temperature graphs, but I get the same result if I manually set the temperature on a single head. Interested if someone has experienced this and fixed it.
     

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