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adenovirux

smoke

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I just change a set of new heating block, peak, insulator, nozzle, thermocouple. And the print becomes a mess.

First, I saw white smoke (I used transparent filament) , which indicates the PLA is evaporating. I then change the temperature from 210 deg (which works very well with the old set) to 180 deg. I also used another thermal sensor to check the temperature is 180 deg. This setting can print, however, the temperature still fluctuating much more vigorous, say +/- 20deg, than the previous set, say +/- 5 deg. From time to time I will see the white smoke, a burned trace, and a sudden release of sticky gel with air from the nozzle.

Anybody have some ideas?

 

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Some possibilities:

1) the power of the heater is much higher now and the PID controller is adjusted wrong. This is very difficult to fix if the heater has twice the power it used to - basically you need to edit configuration.h and lower the max power. Also cut P by the increase in power (if heater is 2X wattage then cut P in half).

2) Bad wiring for the thermocouple. Does the temp vary by 20 degrees over the course of 30 seconds? Or just 1 second. If 1 second then the sensor is having a problem. Could be many things. I would measure the voltage at the output of the board on top of the print head. It should be 0V for 0C and 5V for 500C and linear in between. e.g. 20C is 200mv. Also push the head around to the 4 corners and see if the temp bounces around. Check for loose wires.

3) The wires from the thermocouple to the small circuit board in the print head are VERY sensitive to noise from the fan wires. Separate the fan wires far from the thermocouple wires - 20mm should be plenty. 1mm is too close. Twisting the fan wires can also help but just moving them far away is enough. Obviously this is only a problem when voltage is applied to the fan so starting layer 2 (even if the fan not moving yet).

 

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