Thermal Runaway saga
I bought the i3 MK3 kit last November, assembled it and had no issues printing for several months. Then I glommed up the hotend and was told the best thing to do was replace the hotend. I bought the same hot end and had thermal runaway. Runaway only happened when the hotend started moving quickly over large areas. Upgraded the heater cartridge to 40W and broke the cooling fan. Bought a replacement that was specifically for this printer (eBay). Still had thermal runaway. Bought two thermisters and replaced the existing one. Thermal runaway was now happening after the first layer, when the hotend picked up speed. For a few prints I manually turned off (or way down) the fan after the first layer, these worked. Added into the slicer to turn off the fan after first layer and got a good print or two. Moved my printer into the garage because of the fumes and was able to print a large flat print. Setup another large print for overnight, which printed 3/4 of the way (well past the first layer) then thermal runaway. Tried a different print this morning that consisted of several pieces, none of which were large/flat. Thermal runaway (I think on the second layer).
I did not have to change the fan speed with my original assembly. The new thermisters have a connector in order to replace easier. I replaced the first thermister with the second. The connector is in a poor spot, a little short of the first zip tie. I've added another zip tie to keep the connector from moving
Frustrated and not sure what else I need to do/replace. I just want to print!
Chip
Re: Thermal Runaway saga
I believe you have an intermittent connection somewhere along the thermistor cabling. It can be anywhere from the crimps at the EINSY end plug, along the wire in extruder bundle, your new connector. My particular unit had its issue inside the plug at the EINSY end of the cable. One of the wires was slipping out of its crimp inside the Molex connector. You're going to need to check it end to end - possibly wiggling with an ohmeter attached and watching for changes with movement. You will eventually find the intermittent break.
Re: Thermal Runaway saga
Guy,
Thanks for the reply. So I've been working on trying different things. I did replace the thermister and the cable from the thermister to the einsy board. With that I was able to get 1 print of a larger object. I only zip tied the cable around the outside of the cable sleeve, since it's a pain to disassemble that and the mounted hot end to replace. The replacement thermister I have has a connector, which let me do this. The connector is in a bad spot since it is right under the area between the hot end and the where the first zip tie normally goes. It's hard to place it so it doesn't get in the way. So I wonder if after the first print, something got loosened again. I guess I need to disassemble the darn thing entirely in order to do the tests you select. In the meantime I ordered a thermister from prusa, which should have the better einsy connector. Why is this so fragile?