3D printer Safety issues

Hi!

A few months ago my printer caught fire. It was alone working at home and luckily there were no major problems (only I had to clean the whole house of ashes), but could be a disaster.

I wonder know what options Repetier firmware ofers for the following cases:

1) If the thermistor is removed from hotend. The firmware think the hotend is at room temperature all the time, so send more and more power. The same occurs when the resistance is separated from hotend.
Repetier Firmware compare PWM or power versus temperature change? What functions could I use for safety?

2) The NTC thermistor in open circuit. Then the resistance is infinite and reads minimum temperature at all times.

3) The thermistor is shorted

4) If the user sends order to warm bed and extruder via PC and then disconnect the connection and leaves. Does the firmware turn off after some time if it don´t receives orders?

Regards

Tiwanacote

0.92 has a feature called heater decoupling. That will shut down all heaters if extruder does not heat up while powered.

You also can set min/max temperature inside temp area. If temp outside is measured it is taken as short/missing thermistor killing temperature also.

You should also enable watchdog so firmware resets if the the temperature manager does not get called regularly.

There is no automatic power off at the moment. Not a big deal since set temperatures should never harm a printer. After all some users print days with these temperatures, also I would avoid doing it with extruder to prevent burning filament to walls.

None the less a fire detector is always a absolute must for every printer. There are always unpredicted cases that even with correctly working firmware can happen.

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Thank you!!

For those who want to know directive names in Repetier v0.92:


#define DECOUPLING_TEST_MIN_TEMP_RISE 1 On heatup, we expect at least this temperature rise after the time period set in the extruder. If your measurement is stable, 1 is the value you want.

#define EXT0_DECOUPLE_TEST_PERIOD 12000 For Extruder. msec > Maximum time required to rise temperature by DECOUPLING_TEST_MIN_TEMP_RISE = 1. If rising is slower, heaters will be disabled for safety.

#define HEATED_BED_DECOUPLE_TEST_PERIOD 90000 For Bed. msec > Maximum time required to rise temperature by DECOUPLING_TEST_MIN_TEMP_RISE = 1. If rising is slower, heaters will be disabled for safety.

#define MIN_DEFECT_TEMPERATURE -10 If you are using custom thermistor table don´t forget to add a value < MIN_DEFECT_TEMPERATURE at end of table

#define MAX_DEFECT_TEMPERATURE 260

#define EXT0_WATCHPERIOD 1 You should also enable watchdog so firmware resets if the the temperature manager does not get called regularly.

#define DECOUPLING_TEST_MAX_HOLD_VARIANCE 20 Firmware tests for decoupled sensor - heater. When target temperature is reached, the temperature may only swing this amount or it will mark your combination as decoupled. If you get false alarams after reaching target temperature, increase this value.

Edited 1 time(s). Last edit at 09/24/2015 09:30PM by tiwanacote.