Hotend and bed idle temps off by 10°C
Hello, everyone,
I recently noticed that the hotend on my MK3(kit) was consistently about 10°C lower than the heatbed. For example: If the ambient temperature is 22°C, the heatbed would display around 22°C and the hotend- about 12°C, so the heatbed sensor seems to be working properly. At first I din't really pay much attention to it, until I realized that sice the idle temperature is off, the temp while printing must be off too; The printer would be printing at 225°C when it thinks it's at 215°C. Atleast that's my theory. I've had the printer for quite a while and it didn't do this when I got it.
If anyone knows it there is a temperature offset in the firmware that could be tweaked or can point me to some other soution, it would be greatly appreciated.
Thanks in advance,
Juho
Re: Hotend and bed idle temps off by 10°C
The thermistor table is set in http://github.com/prusa3d/Prusa-Firmware/blob/MK3/Firmware/thermistortables.h . I believe the mk3 uses a Semitec 104GT thermistor in the hotend which would mean that the table in thermistortables.h, you want to look for "#if (THERMISTORHEATER_0 == 5)" and in theory you could edit the table below, however, the error in the temperature is probably not constant, i.e. Just because you are off by 10°C at room temperature does not mean that you are off by 10°C at 225°C. Unless you have access to tools that could accurately calibrate the offsets, this is probably not the best way to deal with the problem.
A better solution may be to just use calibration/test prints to dial in the settings for your filaments of choice. You can try something like www.thingiverse.com/thing:696093. Just pick the level that has the best quality. There are a number of of similar models available to dial in the best settings for your printer. It doesn't really matter that your printer reports a temp of 225°C when in reality it is 215°C as long as you are able to change the print settings to some value that gives you optimal results.
If you really want more accurate values, you could always buy one or two replacements and see if they work better. They are cheap. I think E3D has them. I think this is it: http://e3d-online.com/thermistor-cartridge . (The E3D PT100 is another option but that requires editing and recompiling the firmware and is a bit of a headache because the sensing circuit on the Einsy Rambo isn't really optimal for the PT100.)
I hope this helps!
Lars
Re: Hotend and bed idle temps off by 10°C
In my case the MK2S shows 30 degrees for both hotend and the bed while the real ambient is 22. The infrared thermometer agrees with approximately 7-8 degrees offset also when the hotbed is heated. The offset is pretty constant - I measured 53 instead of 60 with ambients from 21 now to 30 in the summer.
It would be really nice to allow for calibrating the temperature offset in the firmware (and while I am at wishing, E steps calibration directly in the firmware would be nice as well 🙂 )
Re: Hotend and bed idle temps off by 10°C
I'm new to 3D printing and I recently got a MK3S which has been printing very well. However, I had two failed prints because of warping on the first few layers. I suspected the temperature wasn't right across the surface of the bed. So I got an infrared thermometer and the bed when printing at 60 degrees is consistently 5-10 degrees cooler. Ambient is displayed as 51' and the bed is displayed at 60' but the thermometer is reporting as low as 45' on one side. A print I'm doing right now is warping on that side.
How inconsistent is the heat bed across the surface? And how can I fix this? I just think I should set the heatbed to 70' for PLA rather than 60 on my printer.
RE:
Hi Numo,
Did you ever get an answer to making a user adjustment in the mk3 readouts to match the actual bed/hotend temps? It should be doable for Prusa to permit a gcode mod or add a firmware parameter setting to permit the operator to input a temp bed offset of xx degrees so the readout matches the actual (measured) temps and we can all stop guessing. My actual (measured) temps run about 10 lower than readout on the bed and 5 -10 lower on the hotend. Seems to be a common issue.