Hot end Temperature dropping when heated bed is on

General LulzBot TAZ
1

Hello Guys,
Today I started experiencing something very weird with my Lulzbot Taz 5. I’m wondering if anybody has an idea on what is happening.
Whenever I turn my heated bed on my nozzle temperature starts to fluctuate and while printing can drop 10 or 15 degrees.

Because of the symptoms I think it is the power supply not giving enough juice for the printer. Any other guess? or a good way to test the problem and isolate to get to a conclusion?
Already tested setting the temperature using the taz lcd and the same thing happens.

My printer also used to get to the set temperature pretty quick, not it is taking more than 10 minutes for the nozzle to get near the set temperature. I’m sing lulzbot standard firmware.

Follow some charts that I got from octoprint.
Screen Shot 2015-12-02 at 1.12.56 AM.png
Screen Shot 2015-12-02 at 1.26.04 AM.png

2

That started happening to me about a month ago. When I turned the fan on past 50%, the hotend temp started to drop. No issues with the bed though…

I’m also guessing its the power supply. Luckily I print ABS and rarely put the fan over 50%. But I’m starting to think my PSU is going…

3

The heat bed is the heaviest load on the supply. turn on only it and see what the chart shows you. If it drops after a while, you may have a fan problem with the supply, It has a thermal circuit that tries to protect it by lowering the output values(V/A) if possible.(standard supplies at least do this.)

4

Thanks for the reply guys,
After one more night of test, i swapped the extruder and the problem does not happen with a second extruder. So I guess my heater element is somehow damaged and having a weird interaction with the heated bed. I’ll try to analyze the PWM signal for the heater cartridge with a oscilloscope and see what’s going on.

5

Hmm… this is good to know. Could simply be wear and tear on the hotend heater.