Hotend temp issue
I just received my third MK3S in March and was having no problems for the first two weeks. Then I was consistently getting Thermal Runaway in just the first few minutes of printing. It doesn't matter if I'm at 220 C or 235 C. While watching hot end temps I found that the programmed temps are maintained for the first layer while the fan is off, as soon as the print fan turns on the temp will slowly drop until it errors out. I have checked the thermistor, wiring, terminations and fan shroud. All are good. The printer self test revealed no problems. Was thinking I needed to swap out the hot end, but was really disappointed at the need to do this after just a couple of weeks. Then I turned down the fan speed from the default 255 gradually ending up at 225 and, low and behold, the hot end stays within -5C. This is a fix (for now) but my other two printers, which are older by only a few months, haven't exhibited this behavior while using the same filament, same .gcode files, same environment, etc. Any ideas as to why or even will this fix last or just deteriorate further?
RE: Hotend temp issue
One thing that may help is running the PID calibration to better help your hot-end maintain temperature.
For a better fix, install a silicone hot-end sock to shield the hot end from the fan directly. Re-run PID calibration after doing this.
RE: Hotend temp issue
The silicone hot-end sock looks like a great idea. I'll give it a try. Has anyone else had this problem? This is occurring with only one of my 3 printers. Seems odd as everything else is constant through out.
RE: Hotend temp issue
I have not had a runaway but I did have the hotend temperature drop quite a bit when the fan kicked on until the PID was able to adjust and bring it back.
RE: Hotend temp issue
The silicone hot-end sock looks like a great idea. I'll give it a try. Has anyone else had this problem? This is occurring with only one of my 3 printers. Seems odd as everything else is constant through out.
The problem might be aggravated by adjustment of the part cooling fan position. If it's oriented towards the block, it might exacerbate the problem. I'm a big fan of the silicone sock for other reasons myself.
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RE: Hotend temp issue
The silicone hot-end sock looks like a great idea. I'll give it a try. Has anyone else had this problem? This is occurring with only one of my 3 printers. Seems odd as everything else is constant through out.
The problem might be aggravated by adjustment of the part cooling fan position. If it's oriented towards the block, it might exacerbate the problem. I'm a big fan of the silicone sock for other reasons myself.
Seconded. I had a small print detach about halfway through and blob up. The amount of filament would not have been catastrophic, but would certainly have been an unpleasant mess to clean off the nozzle or heat block had I not had a sock.
RE: Hotend temp issue
This seems to be a recurring issue with Mk3s, whereas it wasn't a problem with the Mk3 fan shroud design.
RE: Hotend temp issue
This seems to be a recurring issue with Mk3s, whereas it wasn't a problem with the Mk3 fan shroud design.
Are you referring to the original 90 degree fan mounting, or the later 45 change that mirrors the 3S design?
RE: Hotend temp issue
Either of the those two. I'm not aware of Mk3 R1, Mk3 R2 or the 45° mounted Mk3 R3 were affected by this. But I've seen many Mk3s R4 users reporting that their printer declares a Thermal Runaway because it can't get up to temperature quickly enough between 1st and 2nd layer when the fan is on. And I've seen several claims tha this is because the Mk3s R4 fan shroud design blows a lot more air directly at the heater block than any of the previous revisions did. Can't confirm myself, I went the Bondtech extruder direction, so I don't plan to switch to the Mk3s extruder design.