Thermal runaway after first layer
Total newb here! This MK3s is my first printer and I’ve been at it for a couple days now. With a few successful prints. Sorry if this has already been brought up, but I’m having an issue with thermal runaway after the first layer is spun...
After the first layer the fans kick on and the printer speeds up. That’s when the temperature drops and the printer gives me a thermal runaway warning and the printer stops. I’ve tried so many things including trying to impede the air flow on the hothead fan with a nylon sock. Every time getting the same results. I can print small prints, but anything with a large base is very temperamental. I’ve checked all wires and everything checks out. I know someone here’s got have a quick fix or idea as to what I’m missing.
RE: Thermal runaway after first layer
I've never seen that on my printer (although that is a Mk3, not Mk3s). Make sure both the thermistor and the heater are firmly seated and tightened into the heater block and have a good thermal contact. You can also check the heater resistance to make sure you didn't get faulty unit. A 24V/40W heater should have approximately 14.4Ω of resistance. The thermistor should have 100kΩ at room temperature. Measure both disconnected from the Einsy. Make sure the power supply cables are well connected to the Einsy and tightened. Make sure the voltages the printer reports in the Support menu show 24V while heating. Make sure your fan nozzle is properly mounted as per the assembly manual and not blowing directly at the heater block. Make sure your room temperature is not too cold. With a silicone sock, the temperature drop caused by the fan should be entirely negligible, if it isn't, something is off in a major way.
RE: Thermal runaway after first layer
The MK3S is a bit more sensitive to this: the print fan duct tends to blow more air onto the heater block than the MK3 duct. Certain part geometries will increase the air flow around the heater block, making the issue worse. A photo of your hotend would help, too. I've seen assembly issues that are sometimes surprising.
You should also try running the PID calibration, it compensates for component variation and planned print temperatures.
RE: Thermal runaway after first layer
i had this exact problem too when i upgraded to mk3s and it resulted in quite a few failed prints.
pla was mostly ok but flex didn't work at all due to hotend dropping around 20 degrees in a few seconds (bridging on second layer + change in temp = bad) and unable to recover.
what helped a lot was to get one of those blue e3d silicone sockets, with it on hotend is more isolated from the part cooling fan and making printer more easily able to maintain temperature.
before the i got the silicone cover my workaround was to reduce fan speed to maximum of 70% and i also came up with this little "After layer change" gcode script for slicer pe:
{if layer_num == 1}
;raise nozzle
G1 Z{z_offset+layer_z+10}
;set new temp and wait for it
;with cooling fan on this will likely cause temperature to drop too much
M104 S{temperature[0] - 1}
M109 R{temperature[0] - 1}
;set the real temp and wait for it to come back up again
M104 S[temperature]
M109 S[temperature]
;return to correct Z height
;G1 Z{z_offset+layer_z}
{endif}
the problem i also had due to the large drop in temperature was that sometimes first and second layer didn't stick very well (PETG) and thats what i tried working around with above code.
idea is to first wait until temp have dropped one degree too much (it will be lower) then pause until it comes back up again to the proper temp then continue also lift nozzle a bit so same spot is not heated while waiting.
all of above problems came with the mk3s upgrade, plain mk3 worked fine.
RE: Thermal runaway after first layer
You can also check to make sure your thermistor is completely within the heater block on both ends. I replace mine because I was having the same issue as you, but I suspect the metal part of the thermistor was exposed on one end or the other. The would allow the fan to blow directly on the thermistor and make it think the heater was not able to keep up.