Please redesign your thermistor connection

[Ian Nelson]

Hi everyone,

I ordered my third thermistor for my pico a little over a week ago, and I've just installed it. This one lasted only 5 minutes before messing up. You do realize that the system of using a spring that is screwed into the tapped hole causes the wires to twist around each other, pulling back their sheathing and causing the wires to cross? This is a very poor design.

Consider the following:

Instead of using a spring, which is good to have as a strain relief, but terrible in its current use, an actual screw should be used. Using a larger screw than a #6-40, put thin slices along the opposite sides of the screw to run the wires through. This gives you a sturdy support for the thermistor, as well as ensures that the wires do not cross when screwing the thermistor into place. I'm going to attempt to modify my hot-end to work in this way, and I will be replacing it with something more robust from another company if I can't get this idea to work. I'll post information as I progress on this project.

[Nick Solano]

i do also agree with the way the thermister is attached. currently i have mine kapton taped on.

[Jeff DeMaagd]

Unfortunately, that's the weak point of this design. I ended up drilling it out a bit more and potting the thermistor and spring in place with fireplace cement.

[Brad Stansell]

Agreed.  I have no idea what my thermistor is doing at this point.  It's almost like B3 is trying to trick us into buying the 500C thermistor.  I don't need 500C at this point.  none of my filament recommends higher than 220C, but for some reason at the purported 200C that repetier is reporting, it's vaporizing.  I can't tell if it's a software or hardware problem. 

[B3]

Complain no more guys. The spring design was a step up from Kapton tape and screws holding the leads. Now, we've stepped up even more and I know you'll be satisfied. The spring is fixed into an M3 Hex adaptor that threads in and out of Pico Hybrid or the O.G. Pico. take a look ..more details coming soon..

https://b3innovations.com/?v=7516fd43adaa

Mike

B3

[Brad Stansell]

Great, I just bought the old one and now you come out with a better one.  Here's hoping a better mount accompanies it. 

[brod...@gmail.com]

One way to avoid this, which I've used,is to hold the thermistor and before the hotend is mounted or wired to the board, twist the entire hotend around the thermistor which you're holding stationary. Keep the thermistor as straight as possible. Also, you don't have to twist it in all the way. I often screw it in just a little farther than when it first catches the thread. Then wrap the leads with kapton tape higher up, and the tension of the spring prevents it from popping out. I'm sure there is still some slight torsion on the wires, but this helps to reduce it. This might also lead to a slightly undervalued temp than actual at core, but it should be within 5deg C at most. Excited to hear the updates on the new hotend