I noticed on my last few prints that my printer isn't holding nozzle temp

I noticed on my last few prints that my printer isn’t holding nozzle temp very well. It starts out fine, but over time drifts to 10 degrees or more below the set point and never recovers. I can see on the RAMPS board that the power to the heater is on to the MOSFET (LED is on constantly), but the head isn’t gaining temp.

I can’t recall any changes other than using different filament, but I’ve used this roll in the past w/o issue.

Is this a sign of imminent heater failure? This is my second J-Head, the first blew-out the heater resistor and I’m wondering if that’s what’s about to happen to this one…

Can you check if the heater is actually getting current (as opposed to seeing a light on)?

It’s getting power, and if I back-off my fan it’s able to recover temperature but with the fan running at the proper speed it can’t hold 185c. Until a few days ago, it had no problem at all holding temp even with the fan at full speed.

Sounds like a thermister problem.

How so @matthew_bennett ?

@Jason_Gullickson , have you tried re-M303-ing your hot end?

If it’s not a connection issue, or a thermistor issue, perhaps you calibrated without the fan, and the PID values are driving your hot end too softly?

I haven’t since I originally calibrated it (with the fan on) but I’ll give that a shot; I’m not ruling out that maybe something is awry with my MEGA board in general, it’s had other issues lately and the ADC has always had problems…

have you tried facing a fan to the ramps?

That reminds me of what was happening when my power resistor was on its way out.

That’s what I’m afraid of @Tim_Bertram_bertramt :frowning: I had the same thing happen to my last j-head and I’m not sure if I’m doing something to kill them or …?

I love the results I get from the j-head but if this one dies from the same cause I’m probably going to have to try something else. I have a few heater elements from qu-bd extruders that I might try fitting to one of my dead j-heads (assuming I can get it apart, the first one died a seriously melty mess) but I can’t help but think that I’m doing something harmful to the resistors, seems like they don’t die this frequently for other users.

@Jason_Gullickson what voltage are you running at?

12 volts @ThantiK

@Jason_Gullickson this is what my resistor looked like when it died. https://plus.google.com/u/0/photos/105076878014512274417/albums/5864883570014961777/5864883572859416514

@Jason_Gullickson , you’re properly securing the resistor using muffler-putty or something similar, aren’t you? If the resistor doesn’t have anything to conduct to (is insulated from the walls it sits in), then it’ll have to run at a much higher temp in order to get the hot end up to temp and keep it there.

Yeah @ThantiK I used the aluminum foil method for my first j-head, and switched to muffler putty for the second after the first blew out :slight_smile:

I had a similar problem when I turned on a fan. I ended just putting a few layers of kapton tap around the head which seems to have helped a lot.

Just spend $10 on a ceramic heater. Then you can blow a fan 100% directly at the tip / heating block without any temperature fluctuations.

@Tom_Oyvind_Hogstad you talking about one of those stainless steel heater cartridges? Are the 12v 40w ones pretty good?

I’m talking about the 12V 40W you find on eBay. I’ve used one for 3 months without any trouble. Heats very fast and stay hot.