Extuder not able to reach 255  

Re: Extuder not able to reach 255

I was originally having issues with what I thought had to do with layer fan, then I tried to print in Prusa ABS at 255 and found that my extruder ramps up to about 245 and will go no higher, I have recently replaced the thermistor, heater cartridge, and heater block and I continue to have the same symptoms. I have also triple checked all connections on the Rambo board and all the wiring.

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I have also noticed overshooting of temps, if I switch from higher temp t lower temp it will pass the lower temp by a lot before it recovers and goes back up. Overshooting temps, went from 255 to 220, the temp went as far as 209 before it started to go up.
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I have also tried PID tuning and reflashing the firmware. What else could this be? I was not having any issue before, I noticed the change after I did the MK2S upgrade which I am not sure how that would have affected anything. Could this be a Rambo issue? A power supply issue?

I was talking with support, we tried to raise the temp to 284 to see, the temp rose to about 274, so it seems to be 10 degrees off each time.
Hi,

for which temp did you do the PID tuning? My PID tuning for 205°C and 255°C are quite different and even more from the default settings in the firmware. So i changed the Configuration_prusa.h DEFAULT_Kp/i/d settings to my 205°C (PLA) as default. For ABS i use a different Printer Setting preset for ABS including extra start gcode line for 255°C in Prusa Slic3r 1.34.1.

Having a E3D sock helps a lot to stabilize the temp.

Is your part cooling fan off during ABS printing? Is the environment temperature okay or is it freezing cold? For ABS it even makes sens to enclose the printer to prevent air movement and keep the environment temp bit more stable which also should help with the hotend temp.

Hope that helps.

Re: Extuder not able to reach 255

another idea:
can you check the supply voltage (from the PSU) at the rambo board with a multimeter ?
sometimes it's below 12V.... and the power of the heater cartridge is a function of the voltage².
it should be fairly save to adjust the voltage (at the little trimpot near the terminals at the PSU) to 12.6V (which means +5% higher voltage but 10.3% more power).