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    Heatbed and PID

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    • StaticRedundefined
      StaticRed
      last edited by

      Hey, so im having a question about the heated bed and duet.
      So im using a SSR to controll my 150x150mm bed at 300W.
      Now im not sure whats the best way to get stable bed temps. I tried with bang bang mode for first, and it worked ok with around +-1 degree variation. I also tried with bang bang set to false, but then it will take forever for pid tuning. Its now tuning for almost 1h and not finished by now. Also its going to phase 3, with fan off. Is there a way to turn a fan off for the heatbed?

      my config.yml: https://just-paste.it/k9LfZLJwcT

      jay_s_ukundefined 1 Reply Last reply Reply Quote 0
      • jay_s_ukundefined
        jay_s_uk @StaticRed
        last edited by

        @staticred the fan off is erroneous for heated bed tuning. Just leave it to it and it'll finish eventually

        Owns various duet boards and is the main wiki maintainer for the Teamgloomy LPC/STM32 port of RRF. Assume I'm running whatever the latest beta/stable build is

        StaticRedundefined 1 Reply Last reply Reply Quote 1
        • StaticRedundefined
          StaticRed @jay_s_uk
          last edited by

          @jay_s_uk Im still havin the problem, PID Tuning did run for 3h for the bed. Still no results. I can run it once when no PID values are set in the config. It takes around 15 minutes then to tune in. Afterwards i set the values in config.g and no further pid is possible. Which is sad because im still getting +-1 Degree.

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          • Phaedruxundefined
            Phaedrux Moderator
            last edited by

            What kind of bed plate and heater is it? Can you give more details? Photo?

            What command are you sending to start tuning?

            What firmware version?

            Z-Bot CoreXY Build | Thingiverse Profile

            StaticRedundefined 1 Reply Last reply Reply Quote 0
            • StaticRedundefined
              StaticRed @Phaedrux
              last edited by

              @phaedrux Hey, so im running a 150x150mm Heater with 300w of power. This is controlles by an SSR and with 220v. It then heats up an 6mm thick aluminium plate, the termistor is underneath the silicon heater attached.
              To start PID im doing a simple M303 H0 S60, H0 being my bed heater.
              Running latest Duet RepRap Stable Release.
              Firmware: RepRapFirmware for Duet 3 Mini 5+ 3.2.2 (2021-02-11)

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              • Phaedruxundefined
                Phaedrux Moderator
                last edited by

                What values does it produce once the tuning is complete?

                This?

                ; Heaters
                M308 S0 P"temp1" Y"thermistor" T100000 B4725 C7.06e-8 ; configure sensor 0 as thermistor on pin temp1
                M950 H0 C"out0" T0 Q10                                    ; create bed heater output on out0 and map it to sensor 0
                M307 H0 B0 S1.00                                      ; enable bang-bang mode for the bed heater and set PWM limit
                M140 H0                                               ; map heated bed to heater 0
                M143 H0 S120                                          ; set temperature limit for heater 0 to 120C
                M308 S1 P"temp0" Y"thermistor" T100000 B4725 C7.06e-8 ; configure sensor 1 as thermistor on pin temp0
                M950 H1 C"out1" T1                                    ; create nozzle heater output on out1 and map it to sensor 1
                M307 H1 B0 S1.00                                      ; disable bang-bang mode for heater  and set PWM limit
                M143 H1 S280                                          ; set temperature limit for heater 1 to 280C
                M307 H0 R1.168 C313.3 D6.25 S1.00					  ; bed pid
                M307 H1 R2.798 C162.9:144.9 D7.50 S1.00 V23.7	      ; hotend pid
                

                Z-Bot CoreXY Build | Thingiverse Profile

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                • StaticRedundefined
                  StaticRed @Phaedrux
                  last edited by

                  @phaedrux M307 H0 R1.160 C255.8 D6.62 S1.00 ; bed pid
                  tgese are the current values i use, set bangbang to false and frequency Q to 10

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                  • Phaedruxundefined
                    Phaedrux Moderator
                    last edited by

                    Just to confirm, you've got temp1 thermistor on the heater0 (bed) and temp0 thermistor on heater1 (hotend)?

                    And you've got a semitek thermistor on both bed and hot end?

                    Have you ever let the PID tune run to completion or have you always canceled it after a few hours?

                    Was tuning started from room temp?

                    Z-Bot CoreXY Build | Thingiverse Profile

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                    • StaticRedundefined
                      StaticRed @Phaedrux
                      last edited by

                      @phaedrux Yes for basically all the questions. I once let it run 3 hours, but then stoped it because i had to go away. The PID for the hotend works perfectly tho. I get really like 0 degree variation. But on the bed i just cant get it working.

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                      • Phaedruxundefined
                        Phaedrux Moderator
                        last edited by

                        Can you post a photo of the bed assembly?

                        150x150x6mm and 300W of AC power should heat up fairly quickly, but maybe takes a lot longer to cool down. That's usually what the tuning cycle is waiting for the longest.

                        Z-Bot CoreXY Build | Thingiverse Profile

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                        • StaticRedundefined
                          StaticRed @Phaedrux
                          last edited by

                          @phaedrux alt text so this is what my bed assembly is looking like. Yes it needs kind of long to cool down.

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                          • Phaedruxundefined
                            Phaedrux Moderator
                            last edited by

                            Is that a Voron0? Closed sides but open top?

                            Z-Bot CoreXY Build | Thingiverse Profile

                            StaticRedundefined 1 Reply Last reply Reply Quote 0
                            • StaticRedundefined
                              StaticRed @Phaedrux
                              last edited by

                              @phaedrux its a selfmade printer. Yes sides are closed by now, but top will get enclosed some time soon aswell.

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                              • Phaedruxundefined
                                Phaedrux Moderator
                                last edited by

                                I believe there is plans to make the tuning cycle time limitable in such cases. Not sure when that's coming though.

                                As it is, you can probably get a good tune from it by letting it play out, though with a lot of heat retention that could take awhile.

                                Z-Bot CoreXY Build | Thingiverse Profile

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                                • StaticRedundefined
                                  StaticRed @Phaedrux
                                  last edited by

                                  @phaedrux okay i will let it run trough now, im home all day so i hope it does not take like 10 hours xD

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                                  • StaticRedundefined
                                    StaticRed @Phaedrux
                                    last edited by

                                    @phaedrux so after a bit i got this message this time
                                    Warning: heater behaviour was not consistent during tuning
                                    Auto tuning heater 0 completed after 6 idle and 25 tuning cycles in 2735 seconds. This heater needs the following M307 command:
                                    M307 H0 R1.189 C136.8 D6.60 S1.00 V23.8
                                    Edit the M307 H0 command in config.g to match this. Omit the V parameter if the heater is not powered from VIN.

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                                    • StaticRedundefined
                                      StaticRed @Phaedrux
                                      last edited by

                                      @phaedrux okay so i was able to fix it. I let it run trough for like 4h, then i had it oscilating, so i rised the d value a bit and now im getting a stable temp.

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                                      • Phaedruxundefined
                                        Phaedrux Moderator
                                        last edited by

                                        Glad you got it. A little manual nudging to get it stable is pretty common. The tuning algorithm is still being improved upon to better deal with the edge cases like very large beds or very high powered heaters or chamber heaters etc.

                                        Z-Bot CoreXY Build | Thingiverse Profile

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