PID on bed with 4 heaters
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Hi,
I have a large bed, 525x525mm, with 4 200x200mm 250W silicone heaters. I have the thermistor mouted in the middle of the bed, and I also have one thermistor on each of the silicone heaters (so 5 in total for the bed) .
When I try to do a PID tuning using the thermistor in the middle it won't finnish due to slow heating. When I use "bang bang" mode the thermistors on each silicone heater goes up to around 80c when the one in the middle reach 50c, then ofc the middle one overshoots to around 57c as the silicone heaters cools down. This is greatly reflected as bulges on the print.
So to my question, how can I make the PID work with my setup?
Should I use one of the corner thermistors?(The corner thermistors are setup as virtual temp sensors now)
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Can you share your configuration? How are the heaters connected to the Duet? Firmware version?
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@phaedrux The heaters are connected via SSR, and then the SSR is controlled from the Duet's heated bed output.
I can share the config later today, but it's nothing special. The heaters each have a thermistor that I just "look" at, they are all controlled by the one in the middle which is connected to T1.
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@phaedrux Here are my config.
; Heaters M305 P0 T100000 B3950 R4700 ; Set thermistor + ADC parameters for heater 0 M143 H0 S120 ; Set temperature limit for heater 0 to 120C M305 P1 T100000 B3950 R4700 ; Set thermistor + ADC parameters for heater 1 M143 H1 S280 ; Set temperature limit for heater 1 to 280C . ;Silicone heaters M305 S"Silicone 1" P102 T100000 B3950 C0 X3 ; Silicon mat 1 temp 100k semtek on E2 thermistor input. M305 S"Silicone 2" P103 T100000 B3950 C0 X4 ; Silicon mat 2 temp 100k semtek on E2 thermistor input. M305 S"Silicone 3" P104 T100000 B3950 C0 X5 ; Silicon mat 3 temp 100k semtek on E2 thermistor input. M305 S"Silicone 4" P105 T100000 B3950 C0 X6 ; Silicon mat 4 temp 100k semtek on E2 thermistor input. -
@haggan90 please forgive my saying and or asking this but have you considered purchasing a single 500mm x 500mm ac powered silicone heater powered that is powered and maintained using a solid state relay? I personally use a 400mm x 400mm ac powered silicone heater pad with an SSR and with that Ive been able to essentially get by with a significantly smaller PSU cause the bed heater is powered basically directly from the wall outlet (though it is basically bridged/piggy backed off of the back of the rocker switch that turns the entire printer on so it is also fused too cause the rocker switch has a dedicated AC fuse). I mean it doesnt even have to be AC powered cause obviously there are DC heater pad options I just opted for the ac option. Anyways just wondering though there could definitely be good reason for such a setup that I am just not aware of lols so anyways just wondering man.....
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@pickett I do use AC powered Silicone heaters controlled by a SSR
The reason why I choosed 4 smaller ones was to get a more even heating, and also they cost 1/3 in total compared to a single 500x500mm mat.
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Any ideas?
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@haggan90 said in PID on bed with 4 heaters:
The heaters are connected via SSR, and then the SSR is controlled from the Duet's heated bed output.
So all 4 heaters are connected via their own SSR to the Duet on a single output?
What firmware version? The syntax looks like RRF2.
You may have better luck trying to tune with RRF3.4
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@phaedrux said in PID on bed with 4 heaters:
@haggan90 said in PID on bed with 4 heaters:
The heaters are connected via SSR, and then the SSR is controlled from the Duet's heated bed output.
So all 4 heaters are connected via their own SSR to the Duet on a single output?
What firmware version? The syntax looks like RRF2.
You may have better luck trying to tune with RRF3.4
@phaedrux no, the 4 heaters are run in parallel to one SSR. How tricky is it to upgrade to RRF3? Why would it be better?
I've tested to tune it with one of the 4 thermistors on one silicone pad, the 4 thermistors at each pad differ max 1-2c but the one in the middle is 5-10c lower.
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@haggan90 said in PID on bed with 4 heaters:
Why would it be better?
There has been improvements to the PID tuning algorithm for large slow heaters.
@haggan90 said in PID on bed with 4 heaters:
I've tested to tune it with one of the 4 thermistors on one silicone pad, the 4 thermistors at each pad differ max 1-2c but the one in the middle is 5-10c lower.
That may help a bit.
@haggan90 said in PID on bed with 4 heaters:
How tricky is it to upgrade to RRF3?
That depends on how complicated your setup is.
If you still have access to DWC. Upload these 3 zip files, one at a time in the system tab. Don't extract them first. Reboot after each. Use M115 in the gcode console to verify the firmware has been applied.
https://github.com/Duet3D/RepRapFirmware/releases/download/2.05.1/Duet2Firmware-2.05.1.zip
https://github.com/Duet3D/RepRapFirmware/releases/download/3.0/Duet2and3Firmware-3.0.zip
https://github.com/Duet3D/RepRapFirmware/releases/download/3.3/Duet2and3Firmware-3.3.zip
That will get your firmware and DWC up to date.You can see the change logs here:
https://github.com/Duet3D/RepRapFirmware/wiki/Changelog-RRF-3.xFor your config, might be a good idea to run through the configurator tool and generate a fresh set for RRF3.
https://configtool.reprapfirmware.org/StartBackup your existing config files in the sys folder in case you want to switch back to RRF2. It’s easy to switch back and forth, just upload the zip file for the version you want and then upload your config files.
These documents will come in handy during the conversion.
https://duet3d.dozuki.com/Wiki/RepRapFirmware_3_overview
https://duet3d.dozuki.com/Wiki/Gcode -
@phaedrux I don't really know what defines as conplicated, but it's a markforge(isch) kinematics with 3 independent Z steppers.
Will the code in config differ alot on RRF3?
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The kinematic type just needs to be set with M669
And 3 z axis is easy enough to setup.
https://docs.duet3d.com/en/User_manual/Connecting_hardware/Z_probe_auto_levelling
You'd need to start with a basic config from the online config tool and then make those manual adjustments.
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@phaedrux Ok!
I will give it a go!
Is it the same command (M303) to run PID autotune in RRF3? -
Yes it is.
It would be a good idea to have the gcode wiki open and taking a look at all the gcodes you touch during the conversion to see how they may have changed.
https://docs.duet3d.com/en/User_manual/Reference/Gcodes
You may also find this helpful as well.
https://docs.duet3d.com/en/User_manual/RepRapFirmware/Migration_RRF2_to_RRF3
