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PrusaOwners / Marlin

Optimized firmware for RepRap 3D printers based on the Arduino platform.
http://www.marlinfw.org/
GNU General Public License v3.0
15 stars 4 forks source link

Thermal runaway safety check #17

Closed matthew-humphrey closed 5 years ago

matthew-humphrey commented 5 years ago

See what features we need to add to bring this Marlin port to parity with Prusa with regard to safety features. For example, Prusa has timeout on heaters if printer detects no printing activity for some time. Also, if printer detects that heat is enabled but thermistor value is not increasing, it will also shut off the heaters.

matthew-humphrey commented 5 years ago

I looked into this tonight. Marlin has two features related to thermal safety:

  1. min / max temp - this detects an abnormal reading from a thermistor (typically open or short circuit) and cuts off heaters.
  2. Thermal runaway - this detects a thermistor reading not increasing as expected when a heater is enabled (for example, the thermistor has become separated from the hotend)

Both features are enabled currently. My thought was that these two features were sufficient.

Another feature that Prusa has is to timeout heater after a period of inactivity. I believe the main reason for this is to prevent carbonation of the filament inside the hotend. While we could certain add this, it doesn't seem safety related and is in my opinion a lower priority.