Thermal Runaway
Hello all!
Finally got around to upgrading my Mk2S to the Mk2.5 and having a weird issue. Everything heats up fine, and the first layer prints perfectly but as soon as the printer goes to the second layer and the front fan kicks on the extruder temperature drops from ~210 to about ~190 and the printer fails the print. I am using the new revision of the hot end parts (R3?) with the tilted front fan. Talked to support and they had me reseat the thermistor cable, reset the heater cartridge cable, and re-flash the firmware (was already on the newest). First thought was a bad thermistor (repalcement on order) just wanted to throw it out there and see if that squares.
Thanks!
edit: So I threw on a E3D sock on the hotend and it seems to have fixed the issue for now? The temperature is still kinda wonky but only drops down from 210 to around 206 then bounces back. The only other thing I can think of to point to as an issue is that the front fan isn't stock, the original one that came with the Mk2 kit broke at some point so I found a generic replacement on Amazon that I put in place.
My current theory is that the new fan nozzle was hitting the thermistor itself (somehow) and causing it to read low. Theres no way a fan could overpower the heater cartridge right?
Re: Thermal Runaway
I have the same problem as you since the update I use the old fan nozzle, I think the problem come from elsewhere but I can not find.
tried with old firmware version, same
Re: Thermal Runaway
I have the exact same issue, except with the older, non-tilted version of the hot-end parts, and an original fan. I reduced the fan speed, and that seems to make the drop less severe. Still, it is weird that the temperature readout is so affected by the fan.
Re: Thermal Runaway
Interesting. Another print finished successfully, so looks like my hotend sock ( https://www.filastruder.com/products/silicone-socks-3-pack ) fixed the runaway issue. I ordered the upgraded block/thermistor from Filastruder back when I first posted but USPS seems to be resisting the impulse to actually deliver it. I want to see what happens with the new block/thermistor and no sock just to test.
Re: Thermal Runaway
So I may be some special kinda idiot, actually gave more than a cursory glance at the heat block and the thermistor body was poking out. Probably never cause an issue with the old fan shroud but the new one is a much wider area and was blowing right on it. Oops.
Re: Thermal Runaway
Hi, I had a thermal runaway recently, just as the second layer started, which was annoying as the first layer took half an hour. A retry of the event showed that when the fan started, the nozzle temperature dropped a lot so I stopped the fan and the temperature shot back up again. So the fan is cooling the hot end. I tuned the fan speed until it was not affecting the hot end temperature - 255 down to 155. and all seems well.
I started thinking about this ... The fan is there to cool the recently melted plastic but also cools the plastic that is about to be printed on top of. So if the hot end is cooler than expected and the plastic is cooler than expected, then this might explain the inter layer lack of adhesion problems that I have been experiencing for a long time .. always, actually. If this is a solution to the inter layer problem, I'll let you know. Also about the thermal runaway.
Re: Thermal Runaway
I have had some problems also, with thermal runaway, on my MK2s nozzle, i stared at it until it it stopped, and saw that it was not heating the nozzle enough. After changing the firmware back from V3.1.0 to V3.0.11 (other versions was tried) i have had close to zero problems.