PreHEAT Error  

Re: PreHEAT Error

if everything else is ok with your printer and you have 3.0.10 firmware then the issue is with the fan

"I have experienced this problem and have found that using the print fan while printing higher temp filaments such as PETG can cause this error as the print fan can mess with the thermistor's readings and it thinks that the nozzle can't reach the target temp. Once it struggles to reach the temp for X period of time, the error occurs."

PETG and Nylon seem to absorb heat on their own.

what happens is at higher temps the extruder and bed have a harder time maintaining temperature; At 215 C for PLA it was designed to hold that with 100% fan. but at higher temps the fan has a limit on both the extruder and the bed.
in firmware after 3.0.5 a safety was introduced to prevent a fire. if the temperature of the bed or the extruder drops 15 degrees C for more then 45 seconds a signal is sent to shutdown the printer.

at 240C the unit can barely recover at 40% fan add to that that Nylon and PETG wick heat out and that number drops below 40% cooling fan.

I found at 250-255 C you could not exceed 30% without risk of a thermal shutdown you could get to 40% however you are right on edge of failure and the shape of the part directing the blowing of the fan could trip the error. to be safe and have the extruder actually hold the temperature you want you are limited to 10% cooling fan.

this effects the bed as well until the extruder is high enough away from the bed to reduce cooling and allow the bed temp to recover as well.

so check to see if your cooling fan is running during preheat, add a M107 command if needed to shut it down depending on the software you are using.
if you pass and the print starts again look at your fan settings over 240 you have to be careful and not exceed 40% or risk a drop at or over 15 degrees C

now for other materials like ABS you can run at 255C with the Fan to 100% without problems. ABS doesn't wick heat out like PETG and Nylon.

to confirm, watch your display during a print if you see it drop 15 from where it needs in the bed or extruder then you know that the problem is the fan, assuming everything else is working correctly. a faulty temp sensor can also be the issue. but if you see it work good with PLA and have issues with other materials then look at the fan settings.

Watch autocooling settings or default fan settings they are usually at 100%
This presents a problem that may require custom hand edited Gcodes where you need to blip the fan speed up just for half a layer and then turn it off or go back to a lower setting which is something you cannot do with most slicers. the slicer will take an overall setting per level but not for a sectioned off area. thus you risk de-lamination the temp is too low or thermal errors the fan is too high. it limits your ability to make small items you may need to scale up a design to make it work.

Re: PreHEAT Error

ok thanks I will try to set the fan speed to 40% and give it a try first, it was fan speed 50%max hopefully the 10% make some different.

Re: PreHEAT Error

keep an eye on the temp on the display if you can... i was able to reproduce the failure for thermal runaway over and over so i could see what was going on. then i messed with the fan settings and i could see the upper limit as it held the temp at below 14C from where it needed to be and not trip the thermal error. i then lowered the fan until the extruder and the bed stayed constant that was the floor i could maintain.

so you could setup a test where you expect the thermal alarm to go off, set the extruder high and the fan high and expect failure. then zero the fan let the print complete so even if you get a melted mess you know it isn't the machine tripping the alarm then play with the fan in between to get a range and where you hit the limit with the material you are using.

you may discover you need more fan then possible and in that case you will need to start dropping the extruder 5 degrees at a time hopefully between the lower extruder temp and forced lower fan cooling you can reach something workable.
or you need to switch materials which may not be possible.

for each drop of the extruder 5C you can gain about 5% fans
so at 255 max is like 40% fans with certain materials
at 240 you can hit like 60%.

watch below 10% fans use because the fan may not start up. it needs like a kick start so put in
M106 S125
G4 S1
M106 S25.5

for the Gcode to bump the fan to 50% delay 1 second to make sure it is spinning then drop to 10% or below if needed.

Re: PreHEAT Error

for other materials like ABS you can run at 255C with the Fan to 100% without problems.

Nope. I am plagued with Preheat Error and Thermal Runaway with ABS. Madenning 😡 . Can't print anything. Tried various fan speeds.

Brand new Mk2 just set up last week. PLA prints fine. Other posts are popping up this week for new owners with Preheat and Thermal Runaway issues, and I am beginning to wonder if there is a problem with v3.0.10. Hopefully not defective hardware. All my connections are good.

Re: PreHEAT Error

I have preheat error when trying to preheat to ABS from the menu.

I have the feeling it is some power related problem, like there is not enough power to heat both the bed and nozzle at same time to higher temps.
Like what is mentioned in this thread : http://shop.prusa3d.com/forum/original-prusa-i3-mk2-f23/preheat-error-driving-me-nuts--t4153.html

Im now not using the menu item "preheat" but have instead changed my starting script to first heat the bed and when this is done i heat the nozzle. This works fine for me.

Just to mention, i do not get the preheat error during a print.
I have a case open with support for this, they right now answered back to me and want me to reflash the 3.0.10 firmware to see if it solves the issue.

Also, there is a 3.0.11-RC1 firmware to download wich mentions some fixes for the preheat.
https://github.com/prusa3d/Prusa-Firmware/releases

Re: PreHEAT Error

was going to mention i noticed the new firmware and some heat issues it is suppose to address.
i feel like i will be waiting until other people have good luck with it.

i'm using a large APC with data display and software to see my wattage usage and also to compensate for external power issues.

the first day i used the MK2s i left a 15 hour print and when i came back i had a offset layer. i checked everything and then noticed the APC event monitor on my computer went off while the print was running, i put a APC on the 3d printer and isolated it after that. didn't have that issue happen again.

Re: PreHEAT Error

Just want to let you know that when i reflashed with 3.0.10 my preheat error disappeared.

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Gert