Thermistor/Heater Cartridge Wires Accidentally Cut... Again
 

[Solved] Thermistor/Heater Cartridge Wires Accidentally Cut... Again  

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Michael
(@michael-30)
New Member

I have multiple questions since I'm trying to tackle this recurring issue from multiple angles.

I have an i3 MK3S, and I've had multiple problems with cutting the thermistor and/or heater cartridge wires during regular maintenance on the hot end. It has happened once while cleaning excess plastic from the hot end with a wire brush, and it's happened twice while changing out the nozzle. It's very hard for me to preform either task without my wrench coming into contact with one of those sets of wires. I'm about to buy my 2nd heat cartridge replacement and 3rd thermistor replacement in a year, and it's obviously costing me both my both time and my money.


Since this is reoccurring issue, I'm looking into options for making the thermistor easier to replace. I'd like to upgrade the stock thermistor with an E3D Molex connector cable and detachable thermistor cartridge. This way if I make another mistake during maintenance, I only have to replace the cartridge and not the entire cable.

  • Is this type of Molex connected thermistor/cable combination compatible with the i3 MK3S/Rambo board?


I'm also looking for upgrades to prevent excess plastic from sticking to the heater block or clogging the nozzle in the first place. Less maintenance would mean less potential mistakes, after all. My PLA, ASA, and PETG prints seem to be coming out well with my slicer settings, so I don't believe it's an issue with my slicer profiles. I've also tried attaching a heat sock, but the temperature readings aren't as stable when I cover the heater block with it.

  • Are there printer settings to stabilize the hotend temperature with a heat sock in place?

  • Would a nickel-plated copper heater block help prevent plastic from sticking?

  • Is the Olsen Ruby less prone to clogging than a standard brass nozzle?


I appreciate any advice you guys have.

Posted : 28/12/2020 10:39 pm
Diem
 Diem
(@diem)
Reputable Member

A wrench?

Maybe you need to upgrade your tools; two low profile spanners, 17mm & 7mm plus a soft, copper wire brush will cost less than a new cartridge...

To stick to the block the flament has somehow to go uphill, possibly your nozzle is damaged/worn and filament is curling or perhaps your first layer Z is a little off and your second layer is ploughing the first.

Don't switch to higher tech nozzles until you have a standard issue one working well, perhaps try a new one.

Cheerio,

Posted : 29/12/2020 12:43 am
Peter in Katy
(@peter-in-katy)
Estimable Member

Get a 23mm open end wrench.  Hold on to the heater block front and back.

Get some E3D socks.

Posted : 29/12/2020 1:40 pm
Michael
(@michael-30)
New Member

@diem

I don't believe the Z axis or any bed/mesh alignment is causing issues. I've started running the full calibration wizard after each time I complete maintenance to eliminate that as a possibility.

I've previously narrowed down the nozzle as an issue with plastic beginning to stick to the heat block, but twice now I've cut the thermistor wires when trying to replace one. I'm following the instructions in the Prusa nozzle changing tutorial, using the same types of tools that you've mentioned/are shown in the video. I can take some photos this evening when I get off work.

It seems as though the E3D heat block is designed where a wrench can't make contact with it and not touch the thermistor or heater cartridge wires. Maybe there's another method of changing a nozzle or cleaning the heat block that I'm unaware of?

Posted : 29/12/2020 3:17 pm
Michael
(@michael-30)
New Member

@peter-in-katy

I mentioned that I've tried using heat socks, but unfortunately the hot end temperature starts to fluctuate a lot when one is on the heat block. Octoprint shows it going up to 7-8°C higher and lower than the target temperature. My nozzle clogs even more frequently with the sock on as a result. Maybe there's a setting or calibration I can do to combat this fluctuation?

As for the 23 mm wrench, I'll give that a try. I don't have one that big, but I'll order one so I don't have to make contact with the sides where the wires are.

Posted : 29/12/2020 3:27 pm
JoanTabb
(@joantabb)
Moderator

@michael-30

Hi, if you change the thermo dynamics of the hot end, it is not surprising that the results change, 

have you tried running the PID Tune option with the Sock in position, changing the parameters in this manner will probably return the smooth graph for you. 

the same could happen, if you fitted a copper heatblock or a different power heater. or a different manufacturers thermistor. even changing the part cooling fan shroud can effect the PID tuning

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 29/12/2020 6:22 pm
Michael
(@michael-30)
New Member

I was able to repair the broken wire much easier using the 23mm wrench, and running the PID Tuning with the heat sock on helped smooth out the temperature fluctuation issues. Thanks to both @joantabb and @peter-in-katy for the advice!

Posted : 04/01/2021 5:43 pm
JoanTabb
(@joantabb)
Moderator

Pleased to help

Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 04/01/2021 7:49 pm
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