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So i just finished putting my Max back together after some clean up and now im having issues reaching temp. I ran a PID auto tune for 240(my usual temp) and input those values, but the temp kept falling 5-7 degrees short of target no matter what i set. I did another auto tune for 200 and it has no problem getting there. I decided to use the values from that test and then heat the end to 200 and then manually step up by ten degrees till i hit 250. The first image shows the results. For some reason the manual control page won't let me set past 247. where would i find this limit setting? You can see that the temp makes it in this test but repeatedly drops about 10 degrees before correcting again. at this point the auto tune is failing if i set it for 247 due to never reaching temp and timing out. If i manually set it to 247 it looks like the second graph. It gets there barely but still drops 10 or more degrees each time it droops. Next I auto tuned again for 240 and somehow it made it as you can see in the 3rd graph so i then input those values (likely because i reduced cooler speed from 255 to 200 but idk). With the new values set, I turned on the heater and set it to 247 again. the results are in the 4th graph. Still barely with the same dips but it seemed to smooth out in the middle while i was extruding 50mm runs of plastic.so i set to print and it once again never makes it to start temp. just idles below. Last graph shows this.

Long story short i have no idea whats going on.

So i Finally got it to print. I just set my D to 0 and it just barely reached temp and had a large dip, but after that it was fine. Can I fix this, or should i just run as is for now?

Increase your PID max. AFAIK the default is 205. Kick it to 230 or so.

g.

It was originally on 205 but i already maxed it to 255.

I'm have this same issue. I have tried everything the OP has, as well as re-uploading the firmware, with no luck. (also tried incresing the PID max with no success )

It makes me wonder is something got lose like the thermistor maybe, or perhaps one of the resisters went out?? IDK why it would stop short of temp because of those, or why it would stop heating if the reported temp is not at the set/target temp... but maybe the thermistor came lose and it is actualy MUCH hotter then it is reporting? (man I wish I knew where my IR temp device was so I could check that.)

BTW OP are you useing the stock hotend? Because 250c will damage/melt part of it...

I'm using E3dV6 with a threaded thermistor.

could something be wrong with the rambo board it self... like a bad fuse maybe?

Hi, you can't reach 250ºc because you are limited by the firmware. By default it's set to 247ºc, so you won't melt the stock hotend.
You will need to re-upload the firmware with the changes.

#define MAXTEMP 290 (this one is 247 by def)

#define MIN_DEFECT_TEMPERATURE -10
#define MAX_DEFECT_TEMPERATURE 300 (Extreme values to detect defect thermistors)

make sure to use the right thermistor type, this is the line:
#define EXT0_TEMPSENSOR_TYPE 1 (Mine is b57560g104f)


oh and for the menu settings of the LCD display you need to change:
#define UI_SET_MAX_EXTRUDER_TEMP 290