Extruder not reaching high temperatures

Hello RepRappers,

Problem: Extruder temperature stopped reaching necessary temperatures to print with ABS. For some reason it won't reach the 230ºC required for me to print. It was working fine last week now it reaches only about 170ºC. Yesturday it would reach around 190ºC and the day before around 210ºC.

I have used thermocouple on a multimeter to measure the extruder’s temperature. The readings I was getting in Pronterface and Repetier-Host were accurate. The temperature only reaches about 170ºC. I took the hotend apart and noticed that was the PTFE or PEEK is slightly cracked. Not sure if that could be the problem. I checked if the thermistor’s contacts were properly insulated with kapton tape. One side didn’t seem to be so I wraped it up better and tried heating up the hotend again. No success only reached around 170ºC again. I then disconnected the hotend and measured voltage at hotend’s contacts. 12.5V perfect. Also checked the continuity of the thermistor's wirings, no problem there. I also checked the thermistor's resistance in room temperature: about 100K ohms. The firmware I am running has a table for an Epcos B57560g0107F000. For a long time I was running the machine on old firmware that didn't have any temperature tables. Could this have been the source of the problem?

Now I'm going to research some more about thermistors online. Then I'm going to test the thermistor and research about what current should be running through the hotend resistor and how to measure that with the multimeter.

Anyways, any help will be greatly appreciated!

Thanks

Leo

Oh! I forgot to mention that I started having this problem before the firmware update. Before this problem showed up I had been using the printer for almost a year without any temperature issues on the hot end.

I did have an issue with a clogged nozzle. I had to take it apart to clean it up and when I reassembled it I used a different resistor on the hot end. That didn't give me any issues until now. It has been about 2 months since that nozzle clog happened. The original resistor was 5ohms. The substitute is 15ohms. I had no temperature problems with the 15ohm resistor for the last 2 months until now. I also didn't change anything in my firmware after I changed the hot end resistor during the nozzle cleanup.

Thanks again.

Heater cartridges don't last forever, have you tried a new one? Might be the connection to the board, don't blame always the thermistor or the thermocouple, some time the little guy sweating might need some rest ; )