E3D-V6 thermistor

E3D-V6 thermistor

Postby bbrown64 » 2015-Sep-Mon-10-Sep

I seem to be consuming a few thermistors. Once in a while my E3D-V6 will act up and not heat up. I traced it to the thermistor not telling the software what temp the hot end is. I get a 357 error in Cura. I replace the thermistor and the error goes away and the hotend works.

My question is this: Is there anything more robust that can be used in place of those tiny/fragile thermistors?
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E3D-V6 thermistor

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Re: E3D-V6 thermistor

Postby Mooselake » 2015-Sep-Mon-11-Sep

How are they failing? Are the wires breaking off? Iirc this was discussed a while back, and the fix was to add some support to the wiring.

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Re: E3D-V6 thermistor

Postby RetireeJay » 2015-Sep-Mon-12-Sep

When the thermistor fails, what temperature does it read? These are Negative Temperature Coefficient devices, so a reading of an extremely high temperature indicates a short circuit. Like maybe both leads of the thermistor are touching the aluminum body, shorting out the thermistor. In that case, the solution is very simple: add more Kapton tape to insulate the leads. If there is a broken wire, the resistance will be infinite, which looks like an extremely cold temperature to the Printrboard. That could be harder to fix, depending on where the break is. Anywhere that wires flex is a potential for breakage. The tighter the bending radius and the more frequently the wire bends, the sooner it will break. The break could be in the copper wires leading up to the thermistor leads.

As Mooselake said, you definitely want to keep the thermistor leads themselves from flexing. I try to minimize how much I flex them during installation, and I secure them in a way that they don't flex AT ALL during operation.
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Re: E3D-V6 thermistor

Postby bbrown64 » 2015-Sep-Mon-18-Sep

The thermistor wires are ty rapped to the heater cartridge wires. There is no movement in the wires. I suspect the tiny wires very near the glass bulb maybe touch the heater block. What I am looking for is something more robust than those tiny thermistor. I particularly do no like having to deal with those whisker thin wires. Usually I have to replace the thermistor after the hotend has been moved while printing. This is a failure of the lower part of the extruder not being able to get but 2mm of the cooling fins to clamp to. I know there has got to be a better way to tell the software how hot the hotend is getting, so it can be regulated.
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Re: E3D-V6 thermistor

Postby thawkins » 2015-Sep-Mon-19-Sep

bbrown64 wrote:The thermistor wires are ty rapped to the heater cartridge wires. There is no movement in the wires. I suspect the tiny wires very near the glass bulb maybe touch the heater block. What I am looking for is something more robust than those tiny thermistor. I particularly do no like having to deal with those whisker thin wires. Usually I have to replace the thermistor after the hotend has been moved while printing. This is a failure of the lower part of the extruder not being able to get but 2mm of the cooling fins to clamp to. I know there has got to be a better way to tell the software how hot the hotend is getting, so it can be regulated.


I have dismantled and reassemble my hotends dozens of times, and never had an issue with the thermistors, if you are concerned about shorts, then wrap a small piece of plumbers PTFE tape around the thermistor before inserting it into the hole on the heatblock.

The only other way is to use a thermocouple, but the printrboard does not support those.

Re a better way, those are the only two known methods, there has to be a sensor and you are limited to either a thermistor or a thermocouple.
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Re: E3D-V6 thermistor

Postby evanalmighty » 2015-Sep-Mon-21-Sep

You should post a picture of your hotend install and how the thermistor is placed/fixed in place. Thermistors are thin/fragile, but I haven't managed to break any with the exception of the original Printrbot one. That was a piece.
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Re: E3D-V6 thermistor

Postby RetireeJay » 2015-Sep-Mon-21-Sep

There's got to be a better way of mounting the extruder than with only 2mm of insertion to grab onto! That is your problem; fix it, and the thermistor problem will be solved too.
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GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
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Re: E3D-V6 thermistor

Postby bbrown64 » 2015-Sep-Tue-06-Sep

Jay, I think you have the correct idea. I just need a 3/16" piece of machined flat aluminum, or borosilicate glass. I have already moved the heated bed on top of the side rails. Once I get that done. I will no longer need the spacer that is on top of the E3D-V6. I have already machined down the top fin of the E3D-V6 so it misses the mounting screws for the extruder.
I like the idea of a bit of PTFE wrapped around the wire leads to help insulate them from the hot end. All good suggestions thank you everyone.
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