Hotend temperature rising too "slowly" except it isnt.



  • Hi,

    I seem to have a rate "trip" in the deutwifi that is deciding the hotend temp is rising too slowly and going to fault. Yet I am watching the hot end temperature rise in the web ui and it seems to be rising fine to me. I am getting about 1.4~1.7C/sec which doesnt seem bad. This is a duetwifi inserts into a Wanhao D6.

    I have checked the voltage, I am seeing 24volt at the hotend's plug in the hotend head. The heater has 10.8ohms resistance, I see heating so I am having a wtf? moment.

    I am clearly getting a temperature rise, so is this rate trip adjustable? or I suppose can I turn it off at least to test to see if i get to 260C or not?



  • I have it running at 235C fine, sort of stumped. The chinese wiring is quite small but for 60watts? –> 2.4amps, not a huge load at 24volts. The heating rate would depend on the size of the heater? 10.8ohms suggests 53watts. another its original) heater I have is 10ohms which gives 57watts. I'm wondering if that is a bit marginal for the duetwifi's rate setting? I think I might replace the last of the chinese wiring.



  • You can change the heater model:

    https://duet3d.com/wiki/Spurious_heater_faults_and_how_to_avoid_them

    But 60 watts should heat a whole lot faster than 1.5deg/sec. I would expect about 3-4deg/sec at that wattage. Something is wrong.



  • Annoying….on and off and back on and then it goes to 235C fine....how do I drop this rate limit a few %?



  • Just posted the answer to that above… but the problem isn't the limit, the limit is warning you about something that is out of bounds/unsafe.

    I just tested my 30w heater, 3.5deg/sec.


  • administrators

    Have you run heater auto tuning yet? See https://duet3d.com/wiki/Tuning_the_heater_temperature_control.



  • no never tuned, didnt know I could, will have a go



  • So my initial settings are,

    ===========
    6:40:19 AM
    M303
    Heater 1 is being tuned, phase 3 of 3
    6:34:48 AM
    M303 H1 P0.5 S260
    Auto tuning heater 1 - do not leave printer unattended
    6:29:59 AM
    M303
    No heater has been tuned yet
    6:24:45 AM
    M307 H1
    Heater 1 model: gain 340.0, time constant 140.0, dead time 5.5, max PWM 1.00, in use: yes, mode: PID
    Setpoint change: P13.4, I0.10, D51.4
    Load change: P13.4, I0.95, D51.4

    I set 260C as the upper limit, M303 H1 P0.5 S260 and it tripped at 260C

    What temperature is the tuning meant to go to? kind of wondering as with the wanhao board firmware originally you told it the set point you wanted.

    The heating curve is totally different running this, its way steeper and its convex as opposed to concave….



  • A hole in the wiki,

    https://duet3d.com/wiki/Spurious_heater_faults_and_how_to_avoid_them

    points me at,

    https://duet3d.com/wiki/Tuning_the_heat

    "Tuning the heat

    There is currently no text in this page. You can search for this page title in other pages, or search the related logs, but you do not have permission to create this page.
    "



  • Re-trying P=0.25. painfully slooooow



  • Uh,

    ============
    7:15:49 AM
    M307 H1
    Heater 1 model: gain 626.6, time constant 265.6, dead time 13.9, max PWM 1.00, in use: yes, mode: PID
    Setpoint change: P5.5, I0.02, D53.0
    Load change: P5.5, I0.17, D53.0
    7:14:46 AM
    Warning: Heater 1 appears to be over-powered and a fire risk! If left on at full power, its temperature is predicted to reach 646C.
    Auto tune heater 1 with PWM=0.25 completed in 774 sec, maximum temperature reached 178.6C
    Use M307 H1 to see the result
    7:14:43 AM
    M303
    Heater 1 is being tuned, phase 3 of 3

    ?



  • From what I read I now have new PID settings? its all auto set?

    ========
    7:18:21 AM
    M303
    Heater 1 tuning succeeded, use M307 H1 to see result

    I guess so?

    Too big a heater is a concern? most odd.



  • You now add a M307 H1 line to config.g with the settings M303 found.

    M307 H1 A626.6 C265.6 D13.9 ; hotend pid settings

    The too big heater warning is there to alert you what temp it can reach if it gets stuck on. In normal use, you shouldn't have a problem.


  • administrators

    With firmware 1.17 you can run M500 to write the M307 commands to config-override.g.



  • Thanks but I dont feel brave enough to try updating my firmware yet. I might just leave it until Ive bought a second duetwifi in a month or two so I am not left stuck in the poo if something goes wrong. New ones will come with 1.17 anyway?

    I have not tried running the 3d printer yet to see if its OK as I did this before I left for work this morning and wanted it stone cold before I did as it only seemed to trip at 50~60C or so, once above 100~120C it goes up faster and never trips.

    "normal use" yeah having read the horror stories, I have an arduino mega with a separate thermistor in the heater block (and one in the cold end block and one in the bed). The idea is if the arduino mega sees excessive temperature in either it will drop the SSR powering the d6 out. It got removed while removing the dead wanhao motherboard and installing the duetwifi so I need to put it all back in again. I also have an infra red sensor I want to play with.



  • Wow that is way way faster and it gets to 235C without any 5C+ overshoot and minute or 2 to settle like it did before 😄


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