Stainless tip for thermistor

4

I would like to secure my hotend thermistor in a more reliable way (now it is just thermistor plugged in the hotend :D). I want to have a stainless steel tip for it to fix it inside hotend with a screw (The same approach as used for the heating cartridge). I have thermistors, but I cannot find any tips to buy separately.

Maybe you have some links for this kind of stainless-steel tips? Or some keywords I can use to search them?

Anton Osadchy

Posted 2016-03-07T08:08:59.980

Reputation: 585

Answers

3

The main problem here is that the hot block has to match the temp sensor. There are a couple available commercial options for hotblocks with cartridge-and-setscrew temp sensors, but they're not thermistors:

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enter image description here

Other popular options for thermocouples include a brass thermowell crimped onto the tip of the TC (Makerbot and FlashForge) or an eyelet lug crimped onto the tip of the TC (Wanhao).

The best off-the-shelf solution for most printers is probably to use an E3Dv6 hot block, which uses a screw and washer to clamp the thermistor leads so the glass bead tip can't pull free of its pocket.

Ryan Carlyle

Posted 2016-03-07T08:08:59.980

Reputation: 6 346

Thanks man, "brass thermowell" is exactly what I was looking for. I just didn't know how to call it (maybe because I'm not native English speaker). Other things are really interesting too, thanks for your help. That is the link to thermowells I found: http://www.alibaba.com/product-detail/thermometer-with-brass-thermowell_1780646847.html?spm=a2700.7724838.0.0.vhGi41

– Anton Osadchy – 2016-03-07T17:43:16.787

3

I am not too sure what you're searching for, but I imagine it to be a kind of thermistor housing to distribute pressure from the screw while maintaining good heat conductance.

I first have to say that I'd be afraid to damage the glass droplet of the typical thermistor design by putting pressure to them, especially including later thermal expansion. However, I never tried and we might find some valuable experience on that in other answers here.

If what I assumed in the first paragraph is true, I would suggest forming some housing yourself with copper foil or copper sheets, since the heat conductance of copper is good and it is more or less soft.
However, as a more simple solution, you might just cut the metal part of a 'wire ferrule', if you got some lying around. (Wikipedia has no english article for this, so I link the german one for the images: Aderendhülse)

Additional info: Can't you clamp the thermistor the way it is done in the E3D V6 hotend, see this image?

Thermistor in E3D V6 hotend

Thermal contact should be quite good and you don't have any problems which could lead to damage of the thermistor.

kamuro

Posted 2016-03-07T08:08:59.980

Reputation: 2 804

You understand me 100% right.The think is that it is much chipper for me to buy these enclosures than to spend my time for it. I was sure that such a think exists, but I did't know how to call it. That is exactly what I was looking for:http://www.alibaba.com/product-detail/shanghai-brass-thermowell_60362628006.html?spm=a2700.7724857.29.339.kY5eXu

– Anton Osadchy – 2016-03-07T17:34:47.863

The idea with screw and washer doesn't sounds nice for me because hole is twice as much bigger then thermistor, so I was not sure about thermal conductivity, which can change because of position of sensor. – Anton Osadchy – 2016-03-07T17:39:15.253

3

My thermistors came with a small spring surrounding them, which seems to work pretty well for this (see also E3D Thermistor Alternative). It's pretty close to the size of the spring in an ordinary pen, so you could just try one of those, or you could wind one from copper wire. I always use thermal grease as well, just like you'd use for heat sinks.

image from B3 Innovations - Thermistors (Gen1)

Thermistors (Gen1)

TextGeek

Posted 2016-03-07T08:08:59.980

Reputation: 3 081

1

Your link to the image has expired, it would have been a good idea to include the actual photo in your answer (in case of the inevitable link rot). I have had a search, is this what the photo was of? If so, would you like to edit and add it to your answer? image from Thermistors (Gen1)

– Greenonline – 2018-08-15T08:23:14.023

Can you take a picture please? I don't really understand how it can work :/ – Anton Osadchy – 2016-03-07T17:27:54.567

Here's a link to the picture from B3 Innovations, where I bought mine: https://www.b3innovations.com/wp-content/uploads/2013/12/Pico-Hot-end-e1417577727405.jpg This shows it installed on a hotend, but they sell the "thermistor assembly" by itself, or as mentioned you could do something similar.

– TextGeek – 2016-03-07T17:33:35.337

Aha, looks really nice. It can prevent wire from banding, good idea. Thanks a lot man. – Anton Osadchy – 2016-03-07T17:45:30.130