[3.6.0-beta.4] heater feed forward leads to heater faults
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I experimented with the heater feed forward for my hotend, but couldn't avoid constant heater faults. When enabling any amount of feed forward or temperature increase based on feed rate, I got a steady stream of "temperature rising much more slowly than the expected" errors. The "actual" numbers were all over the map, with some negative. I suspect this is because my hotend responds much slower than the feed rate changes, and the heater fault tracking doesn't handle this situation very well. Maybe it doesn't work when the setpoint moves faster than the dead time?
My heating process parameters are
M307 H0 R1.900 K0.131:0.000 D9.00 E1.35 S1.00 B0 V25.4, from an auto calibration run. Those seem fairly correct to me, I don't get any heater faults normally and it holds temperature fairly well. There's a large delay between changing anything (heater PWM, feed rate, or part fan) and the temperature responding, I suspect because the heater cartridge is on the far side of a big copper block from the temperature sensor. I tried turning up the heater fault detection time, which definitely increased the time between heater faults but did not avoid them.I was previously running 3.5.2, and I had a
M309 P0 S0.12but I'm not sure it ever did anything. After upgrading to 3.6.0-beta.4 I had to remove it.My config.g (with the feed forward commented out) is attached: config.g
My printer is a CreatBot D600 Pro with an almost-entirely custom control system and print head (tldr: big cartesian printer with heated chamber and a 600mm x 600mm x 600mm build volume). The print head is a Hemera XS and SuperVolcano, with a 1mm brass nozzle. The X and Y axes each have a single JSS57P1.5N integrated digital hybrid servo (stepper motor with an encoder and servo controller attached to it which takes step+direction directly). The X and Y axes are controlled from the mainboard stepper expansion header, via a 5V level shifter. The Z axis is a stepper (57HS76-3004A08-D21-16 I think? haven’t flipped the printer over to confirm) driven by a MKS TB6600 V1.1, controlled from a custom expansion board. I’m using PrusaSlicer (config bundle attached, renamed to .txt). The control system is a Duet 3 Mini 5+ mainboard, a custom Sammy-C21-based expansion board, and a Duet 3 Toolboard 1LC in the print head. They’re all running 3.6.0-beta.4, with a few changes to the config #defines in Config/SAMMYC21.h.
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@bsilver8192 Please look at
https://forum.duet3d.com/topic/36364/feature-adaptive-feedforward-temperature-setpoint/21
You need to loosen heater check even more.
