1 Topic by compchemist

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Topic: extruder overheating after replacing thermistor

hi all,
I'm running a DaVinci 1.0a with stock 1.0.3 firmware. My original thermistor wire broke so I replaced it with a RioRand 100kohm NTC thermistor off Amazon. Everything seems to have gone back together fine, but when I test it out by using the load filament on the menu, I have problems. The display shows it getting to about 205C and still heating (but display T not rising any more), but at the extruder I get smoke and bubbling and it's clearly burning the filament. Something seems wrong in the way the machine is reading the thermistor T.

I see posts about changing the thermistor table using Repetier, but I'm on stock firmware and would prefer that if possible since I don't have time at the moment to learn the new firmware. I print with Simplify3D and have been reasonably happy with that so far.

Any suggestions on what might be going wrong, or what I could test?
thanks!

2 Reply by barry1685

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Re: extruder overheating after replacing thermistor

OMG... I bought the same thermistor and it does the same thing, except it only gets to 140C max. I don't know if the temp is correct though. I didn't get any burning yet.

3 Reply by barry1685

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Re: extruder overheating after replacing thermistor

Not sure if this helps, but I was suggested to use a CPU thermal compound because the a thermistor that has readings that are messed up are due to the thermistor not touching the hotend correctly. So I am going to use a cpu thermal compound and will seal the end with RTV.

4 Reply by carl_m1968

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Re: extruder overheating after replacing thermistor

barry1685 wrote:

Not sure if this helps, but I was suggested to use a CPU thermal compound because the a thermistor that has readings that are messed up are due to the thermistor not touching the hotend correctly. So I am going to use a cpu thermal compound and will seal the end with RTV.


This link might help. Gives some general theory and trouble shooting  ideas.
http://reprap.org/wiki/Thermistor

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5 Reply by silveradept

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Re: extruder overheating after replacing thermistor

I am about to go through the process of replacing my thermistor.  Any tips on getting the old one out, maybe with pictures?
I have a DaVinci 1.0a and I broke one of the thermistor wires.

6 Reply by barry1685

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Re: extruder overheating after replacing thermistor

Yea you need a new table so you can't get that thermistor to work on stock firmware. You need to find a thermistor with the correct beta number as the davinci

7 Reply by evanalmighty

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Re: extruder overheating after replacing thermistor

Your best bet is to find another 100K thermistor.  I know the EPCOS 100K is very popular, so it might be the right one.

8 Reply by barry1685 (edited by barry1685 2015-04-10 21:07:18)

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Re: extruder overheating after replacing thermistor

I can try and look up what thermistor is used generically in repetier which would support your davinci extruder. EPCOS needs a seperate temp table to work.

9 Reply by barry1685

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Re: extruder overheating after replacing thermistor

I also need to know what davinci model you have 1.0 or 1.0a

10 Reply by compchemist

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Re: extruder overheating after replacing thermistor

I have a 1.0a. Thanks!

11 Reply by barry1685

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Re: extruder overheating after replacing thermistor

I bought a thermistor online that works pretty well so far. I went up to 220C without anything burning.

This one worked for me. http://www.amazon.com/gp/product/B00THZ … &psc=1

12 Reply by asiddiqui86

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Re: extruder overheating after replacing thermistor

Use the thermistor Barry1685 said to use and use exhaust cement in a tube to ensure that it can heat up and doesnt get damaged.

13 Reply by barry1685

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Re: extruder overheating after replacing thermistor

So I found out Davinci's circuit board changes the resistance to the thermistor making it difficult to replace the thermistor (in other words xyz makes their thermistors custom) I think davinci uses a lower beta than 3950. But I haven't had time to find the beta that is used in rep for davinci thermistors, so I'll get that info soon if I can find it.

14 Reply by tedh98

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Re: extruder overheating after replacing thermistor

I have a 1.0A and the original thermister got ripped out during a print job gone bad. 

I bought this one:  http://www.ebay.com/itm/291385773137?_t … EBIDX%3AIT

and drilled a hole on the top of the extruder for it.  http://soliforum.com/i/?4XvbUcW.jpg

I've had no problems with it and hopefully with the thin wire more out of the way, it will stay better protected.