PID Tuning fails at 255

  • Hello again everyone. My Upgraded HE280 hotend (my second one) has always had trouble maintaining temperatures above 240 when the fans kick on-- something I've posted about here before. It's resulted in many failed prints right at the start as my thermistors "def". The material I am printing is PCTG for prosthetic sockets, which I've found is comfortable between 245-255. What I've read is run your autotune hotter than the material you intend to print. In the command console I input M106 to get the fans up to max then run the calibration M303 P0 S255 X0 and the PID tuning continually fails. I successfully tried running it for 245, but when trying to print higher than that the hotend never comes close (I think the target E0 was 255 and it only got to 235). When I try S255 for the PID autotune the highest my thermistor can achieve is 253. What's the deal.

  • Just to follow up I reduced the Fan speed to about 50% and ran tuning. I could get a successful tune at 250, but not 255. I just set the printer to 270 to see if it can get up there at all and it did. That was with the hotend high above the plate with the fans on. As soon as I lower the hotend to the plate it starts dropping. I looks like the best it can do is around 260. It's had issues in the past even getting up to the desired temp and never starting prints before, but tuning usually fixed it up until now.

  • Sounds to me like your heater just isn't powerful enough to overcome the cooling fans. When you lower the nozzle toward the bed, you get more blowback from the fans, which cools the heater block. You probably just need to turn the fans off when you are running that hot.

  • There's multiple setting in firmware that causes the print head to disable at temperatures higher than 240ish. Go into the updated firmware supplied by seemecnc and in the master config file in Arduino use ctrl f to search "temp". youll notice some max settings are set to 240. change those to 270. even though he280 can go slighter higher im not familiar with any filaments that require that high of a temp.

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