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Improvement on Thermistor mount and wire management!!!

Posted by rossfree 
Improvement on Thermistor mount and wire management!!!
December 08, 2018 10:11AM
I've been struggling to share these pictures but it's the only way to properly describe what I did...

I've always hated the difficulty attaching the glass bead thermistor to the hot end. It is usually held in by the head of a screw gently squeezing the wires and holding the glass bead in a hole but it sucks at best.

What I did was make a small oblong washer of teflon. I punched two holes in it. The screw goes through one. The thermistor wires are split to go around the screw and then pass through the second hole. For added measure, I used a Dremel cutting disk and put two very small grooves in the block on either side of the screw hole. I nest the two thermistor wires in the grooves as I insert the screw. As I tighten the screw, the teflon serves to isolate the turning action of the screw head from the wires while gently gripping the wires against their respective grooves. The second hole in the teflon serves to protect side pull on the wires that might otherwise dislodge the delicate wires from under the screw. I can now service the effector assembly without worrying about damaging the delicate thermistor wiring!!! I have provided links to pictures below. It was the best I could do to provide pictures which explain better than I can in text.

Happy Printing!!!

Ross

[drive.google.com]

[drive.google.com]

[drive.google.com]


You don't need a parachute to skydive. You only need a parachute to skydive twice.
Re: Improvement on Thermistor mount and wire management!!!
December 08, 2018 10:43AM
Teflon and heater blocks are a bad combo. Thermistors usually come with glass sleeving to put on the leads because teflon softens and can start to decompose a hot-end temperatures. That's also why hot ends with teflon liners that go into the heater block are bad.

It would be better to use ceramic or some other material that won't be affected by the heat.

Glass bead thermistors are passe. Get a cartridge type- they have better thermal coupling to the heater block.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Improvement on Thermistor mount and wire management!!!
December 08, 2018 11:09AM
Well, I wasn't expecting that the first reply I received would be aimed at shooting down my suggestion. As I worked as a design engineer for a company that made teflon products for the medical industry for twelve years, I can assure you that under the conditions I have suggested, the PFTE material will absolutely do the job with out any significant degradation. Unless you are melting materials exceeding 600 degrees F you won't even begin to melt PTFE which really isn't a thermoplastic anyway. It is skived from a billet of compressed material into sheet form. It is a soft material and can soften as you approach 600 degrees but beyond that it is entirely acceptable in this application.I have three printers, two that I designed and one that I purchased. All three have glass bead thermistors. They work just fine and I am not in a rush to spend the money to upgrade any of them at present. I am sure there are thousands of printers out there that still use glass bead thermistors. Replacements are cheap and easy to come by and for the first time, with this modification, easy to install and robust in use! Why wouldn't I want to share this new knowledge with everyone!

Don't put down other's ideas for the sake of having something to do with your time without first trying it yourself.

It works just fine!

Ross


You don't need a parachute to skydive. You only need a parachute to skydive twice.
Re: Improvement on Thermistor mount and wire management!!!
December 08, 2018 01:08PM
It isn't a matter of putting it down. It's years of experience- look of some of the posts from people who have had hot-ends with teflon in the heater block. I've used some cheapo PT100 sensors that had teflon insulation on the leads going into the sensor and after a few hours of operation, they short to the heater block because the Teflon breaks down.

It's great you're thinking about wire management- hot ends usually don't really have any provision for that. I just don't think Teflon is the way to go.

How long have you been using it that way? What materials do you print?


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Improvement on Thermistor mount and wire management!!!
December 08, 2018 05:02PM
Hi rossfree,
I have used PTFE insulated thermocouples on my printers - the PTFE is rated for continuous use at 260°C so it is good so long as you don't get experimental at higher temperatures. One of my other printers has a glass bead thermistor held in by little more than hope - although it hasn't fallen out yet but I wouldn't recommend this. I will adopt your idea to hold the thermocouples in the printer I am presently building - how to hold them in is an item I had not considered until now.

Mike
Re: Improvement on Thermistor mount and wire management!!!
December 08, 2018 07:43PM
can of coke cut down & wrapped around sensor and shoved in hole(with paste that performs) or even a washer made of it(maybe silicone better) to replace ptfe/teflon.

Edited 1 time(s). Last edit at 12/08/2018 09:57PM by MechaBits.
Re: Improvement on Thermistor mount and wire management!!!
December 09, 2018 04:12PM
A simple grommet, two sides bent to make a U to hold the two wires protected by a fiber glass sleeve "et voila" !

No Teflon! It will soften, creep, won't stand the T° needed by some filaments (All metal hotends exist for a reason).

A cartridge like can be made with a simple brass M3 or M4 short screw drilled lengthwise to pass the wires. Screw it in the hotend tapped hole. It is what I use.


"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)
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