extruder stops heating mid print

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Kamo 2pcs Cartridge Heater for 3D Printer (24V/40W)

Please, tell me you are not using 24V types?!

The cables of the heater are looking quite burnt...
The cartridge is almost not touching the hotend in the last pic. You are not trying to print that way?

A bit insulation around the hotend would help, too...
-Olaf

About the only possibility of reading it in-circuit would be getting a reading that is low . . . . so not a factor here . . . it's already way too high . . .

- Tim

That's a 24V heater element you linked to, which matches the resistance you measured. You need a 12V heater. And like Olaf said, why is it so far out of the block?

Edited 1 time(s). Last edit at 06/21/2015 02:59PM by JamesK.

AHHHHH...what a mess!!
But that's not what we are here to discuss, so back to the issue at hand:

As stated above a couple of times: 24V/40W is the wrong heater. The resistance you measured is fine for the heater, but the heater might not be fine for your printer! A 40W heater at 24V will only output 10W at 12V (the power output is proportional to the square of the voltage). That's probably not going to be enough.

And I think that thing sticking out of the hotend is the thermistor, is that right? The thicker cables at the back are probably the heater. I don't think that sort of arrangement with the thermistor will give reliable temperature results. And why are those cables burnt?

One other thing: you don't try to print with all that goop on the nozzle do you? It could affect the print quality. If I get build-up on my nozzle, I wait til it's hot then a quick wipe with a paper towel.

As for the resistance measurement, the way you did it is fine. What I was trying to get you to do was take TWO measurements: one when things were fine, and one when things were not fine. If the resistances were (significantly) different, It would confirm the problem was with the heater or its wiring. It's probably not so important now as you would be best getting yourself a more suitable heater, and maybe fix up the thermistor setup (if I am mistaken then forgive me, but it just looks wrong to me..).

Eric

And just one more (unrelated) observation: I notice the top corners fix the top of the Z-threaded-rods in place. This is generally considered to be a bad thing. If there is any amount bow in the threaded rods, and the top and bottom are held tightly in place, the bow will affect the X-carriage.
Have a look at this article on z artifacts:
evernote article on z axis artifacts

Eric

From the last picture, I´d almost bet the wires are soldered and not crimped. The heat from the cartridge melts the solder and cause intermittend contact.
-Olaf

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And I think that thing sticking out of the hotend is the thermistor, is that right? The thicker cables at the back are probably the heater. I don't think that sort of arrangement with the thermistor will give reliable temperature results. And why are those cables burnt?

Ah, good call - the thicker wires at the back are clearly a better match for the linked heater. But I've never seen a thermistor in a metal package before - what's that about?

the thicker red wires are the heater. and the metal thing sticking out is the thermistor its slightly burnt because i overdid with the heatshrink abit ( the metal thing came with the kit do you recommend i should change the thermistor setup? )

so i just ordered these heaters
[www.amazon.com]

i cant believe i haven't noticed its 24v but thanks for pointing that out guys

and thanks alot guys for the help and the tips i'll do most of the things you told me to do. I really do appreciate the help and if you recommend anymore changes for my printer please do tell ( the thermistor should i kapton tape it on the block it self? )

If it gives reliable temperature measurements then I guess it's all good. I just hadn't seen one like that before. I've seen small glass beads with both wires on the same side [reprap.org]
and in-line glass packages with a wire on either side
[reprap.org]

In both cases you want the thermistor inside the heating block close to the nozzle to get a fast responding and accurate read on the temperature that the plastic is experiencing.

ye the thermistor is the glass one but its inside the metal tube.
should i take the thermistor out of the metal tube and kapton tape it to the block?

I'm not sure, it will be interesting to see what someone with more experience suggests. One of the things that I've wondered about my hotend is that the thermistor seems pretty loose in the hole and it doesn't look like it would make a good thermal contact. I've wondered about trying to seal it with thermal grease, but I was worried that the grease might be conductive and alter the reading. If the thing you have has the thermistor already bonded to a tube, and then the tube is a good fit in the heating block then that might actually be a really good solution to the problem. Just make sure that there's plenty of contact between the block and the metal tube.

I guess the metal tube is there to protect the thermistor from damage from the grub screw. Where in the tube the thermistor is is hard to say. It would want to be in the part of the tube in the head, if it is in the part of the tube that is sticking out, it will be measuring lower.If it is in the part of the tube under the grub screw, I wonder if the grub screw itself could be too tight and causing damage? Just a thought.
I just have mine in the cavity made for it and held in place with high temperature tape.
I don't think thermal paste would be necessary for the thermistor. The amount of heat transfer to bring it up to temperature is pretty small (compare it to the 25W+ the heater has to dissipate).

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blabbersnitch
I don't think thermal paste would be necessary for the thermistor. The amount of heat transfer to bring it up to temperature is pretty small (compare it to the 25W+ the heater has to dissipate).

In case of the thermistor it´s not about the amount of energy that is transferred, but lower hysteresis / faster response .
-Olaf
@JamesK
Thermal grease is nonconductive, even the best "silver"-grease uses silver-oxide, which is nonconductive.

You should disconnect the heater wires from the Ramps board first then measure the heater resistance on the ends of the wires.
Also, is that heater tube really sticking out the back that far or just pulled out to show it?

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Waitaki 3D Printer