Thermal Putty for Thermistor/Thermocouple

Has anyone tried something like this - [www.mcmaster.com] for use with the thermistor or thermocouples. Its rated for 750F and they also sell one rated for 1250F, the only concern I have with it is that it "hardens like a rock" and the possibility of losing a heater block if you use it. I've also been looking at graphite grease for use with my thermocouple probe but its only rated for 260C and is conductive so would not be any good for thermistors.

I recently had to put a new heater block on my printer after I ruined the old one. While I was doing it I added some Thermal paste from Fry's (I think it was EARCH:MAIN_RSLT_PG" target="_blank" rel="nofollow">Masscool Stars-700 Thermal Paste. While I didn't record or take any screen shots before, to me it seem like my temp is more consistent. I was warned to make sure not to get the thermal paste on the wires coming out of the resistor so as to not short circuit it.

As for thermal grease, when I was at Fry's the tech did not recommend it. He looked at what I was doing and said it was far liquid and would likely run out.

On a side not make sure you use some anti seize if you are putting together threaded components. I used some spark plug anti-seize thread protector paste from PepBoys. Though one of these substance released some steam/smoke when the hotend heated up for the first time.

---

--------------------------------------------------
Check out my blogs: [oc3dprint.blogspot.com] & [forums.reprap.org]
Hit me up if you have any tips or tricks.

Quote
TheyCallMeJohn
I recently had to put a new heater block on my printer after I ruined the old one. While I was doing it I added some Thermal paste from Fry's (I think it was EARCH:MAIN_RSLT_PG" target="_blank" rel="nofollow">Masscool Stars-700 Thermal Paste. While I didn't record or take any screen shots before, to me it seem like my temp is more consistent. I was warned to make sure not to get the thermal paste on the wires coming out of the resistor so as to not short circuit it.

As for thermal grease, when I was at Fry's the tech did not recommend it. He looked at what I was doing and said it was far liquid and would likely run out.

On a side not make sure you use some anti seize if you are putting together threaded components. I used some spark plug anti-seize thread protector paste from PepBoys. Though one of these substance released some steam/smoke when the hotend heated up for the first time.

[shop.advanceautoparts.com]

I found that locally and it seems to be roughly the same as the mcmaster stuff, I will go get it and try it out. I'm trying to eliminate my thermocouple swings and there is quite a bit of air around the thermocouple.

I use thermal paste on my thermistor to get better heat transfer and therefore better temperature readings. I wrapped the thermistor and heater block in self adhesive silicon tape from my local Advance Auto Parts. It's self adhesive and high temperature found int he exhaust section. From what I've read, it's grip INCREASES as it gets hot. I saw the tip on a youtube video showing a hot end build. I haven't used mine much since doing it but it seems like it should work better than a kapton wrap.

The main problem I see with the putty idea is that it won't be repairable if your thermistor breaks.

I have the feeling that just using kapton over the hole when the thermistor is in, closes it off enough. And then I add one layer of ceramic insulation over the whole brass block of my J-head to finish it off nicely. Can't go wrong with that

I'm using a thermocouple which is fairly bulky (It's actually rated to handle 350C+ including the leads, I'm hoping this putty hardens and holds it in as well.

Could you put the whole thing in high temp heat shrink tubing (rated to 260C to keep the parts in?

[www.cableorganizer.com]

It would be kind of an expensive solution unless you could buy it in short pieces.

---

--------------------------------------------------
Check out my blogs: [oc3dprint.blogspot.com] & [forums.reprap.org]
Hit me up if you have any tips or tricks.

Quote
TheyCallMeJohn
Could you put the whole thing in high temp heat shrink tubing (rated to 260C to keep the parts in?

[www.cableorganizer.com]

It would be kind of an expensive solution unless you could buy it in short pieces.

I need at least 350C

I use Braided Fiberglass Sleeving Impregnated With Silicone - one on each wire - must be the silicone impregnated tubes - not other plastics

[www.alibaba.com]

Quote
Xabbax
I use Braided Fiberglass Sleeving Impregnated With Silicone - one on each wire - must be the silicone impregnated tubes - not other plastics

[www.alibaba.com]

Maybe this wasn't clear, this isn't for covering the wires. It's for better thermal conductivity inside the hole that the thermistor/thermocouple goes.

Why make it harder (and messier) than it needs to be?

Screw-in thermistor. Problem solved

Screw-in Thermistor

Quote
tjb1
[shop.advanceautoparts.com]

I found that locally and it seems to be roughly the same as the mcmaster stuff, I will go get it and try it out. I'm trying to eliminate my thermocouple swings and there is quite a bit of air around the thermocouple.

That's not what I was referring to I was referring to the spark plug anti-seize to put on your threaded components. I personally wouldn't put any of the solidifying putty on my thermistor or resistor.

I also realize u were looking for thermal conductivity. I think people were just suggesting alternate ways to keep the thermistor in with using a paste that solidfies. If u have your cables properly secured like they are in the Budaschnozzle regular heat sink paste should work fine. Then you aren't stuck with your thermistor permently imbedded in the block.

---

--------------------------------------------------
Check out my blogs: [oc3dprint.blogspot.com] & [forums.reprap.org]
Hit me up if you have any tips or tricks.

Ok I just mentioned a thermistor in the title for others....I am using a *thermocouple*, it is fairly heavy wire (much heavier than a thermistor) and the point I am making is there are only VERY FEW compounds that can handle 300C.

No heat paste for a computer can handle 300C, PTFE tubing melts at this temp, thermistors die around this temp, heatshrink melts at this temp.

I am trying to find something that can fill the hole, provide better thermal conductivity than AIR, and handle the temp which is why the title talks about thermal putty.,...not paste, ptfe tubing or heatshrink.

I don't think many of you know what proper thermocouples are like, they are hard and stiff and I am having trouble with kapton even holding them in wrapped multiple times around the heater block. I am also having issues with temp swings because it takes a little longer for the block temp to affect the thermocouple which is why I am looking at these paste options.

Edited 1 time(s). Last edit at 01/19/2014 04:30PM by tjb1.

... for measuring temps until 600 degC I'm using PT100 sensors and pastes/fixtures mixed from ceramic dust and waterglass (soluble sodium silicate) ...

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Sodium silicate muffler putty or cement are easy to find and popular for cementing heaters and thermistors in hotends. It should work fine for a thermocouple, and is brittle enough to chisel out with a small pick.

Make sure that the junction is insulated first. Chasing down inadvertent current paths in a thermocouple system is not fun.

Viktor,

Using PT100 sensors causes some changes on the Vref, R2 and capacitor. OMEGA has cheap PT100 and PT1000 sensors, but the wiring change to my RAMBO keeps me from trying it.

Did you just assign another pin and make a separate circuit off board?

I've looked but can't find details and wonder how you solved this.

Dave

Hi Dave,

... we've discussed this via PM, but could be helpfull for others, so I'll post the essentials here too:

I've used them with another µC (ADuC847) with a builtin 24Bit AD-converter 'straight forward' as linear sensor with a simple voltage-to-temp conversion/calculation.

For controlling the temperature accurate to 0.02°C we had a sort of PID, but you can run it as bang-bang too ...

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Quote
Xabbax
I use Braided Fiberglass Sleeving Impregnated With Silicone - one on each wire - must be the silicone impregnated tubes - not other plastics

[www.alibaba.com]

Did you have to order a thousand metres?

---

_______________________________________
Waitaki 3D Printer

I did use VersaChem - Muffler Joint Sealer:
http://www.oreillyauto.com/site/c/detail/VER0/10160/N0073.oap?ck=Search_N0073_VER_-1_3474&mn=VersaChem&mc=VER&pt=N0073&ppt=C0022
for attaching a thermistor to my heatbed. I defensively recommend using screw in thermistor/thermocoupler instead since this becomes hard like concrete ('sets like a weld') and makes replacement next to impossible.
It has high temperature resistance at 1000 Degrees F and intermittent temperatures to 1500 Degrees F.
I did see a thread rating the thermal conductivity very high (same as heat-sink paste) which is fine for this purpose, however that makes it useless as a replacement for Peek as an example.
So I don't see much use for it at all, unless you have a rusty muffler....

You could fill the well with silicone thermal compound, then cap it off with the Muffler Joint Sealer to retain it.
Test/validate your assembly for reliability, e.g. if the thermistor falls out you could create a fire hazard.

I'll create a new thread when I get the Omega RTD working as well.
Should be a simple circuit that uses the Marlin lookup for PT1000, PT100 or that style.

Our goal is to provide a voltage instead of a resistance, for the input of the voltage divider on the board.
Should go straight through to the ADC, and be ranged as needed.

This renders the hard to change pullup and Vref pretty much irrelevant.

turns out that Marlin is amazing and can read the RTD using the onboard voltage divider setup with the 4.7k pullup resistor.
Using a pot resistor, I measured a 12 ohm shift along all values, as reported by the host.
This test measures the pot unhooked from the RAMBO, as it's affected by the pullup.

This means the RTD characteristics/curvefit was shifted by this amount.
I simply modified the math in thermistortables.h and now the ohm reading matches the datasheet versus temperatures (from host).
My next testing will calibrate the RTD versus a thermocouple, using an actual heated block.

I used the type 147 PT100 with a 4.7k pullup.

#define PtA 3.9083E-3
#define PtB -5.775E-7
#define PtRt(T,R0) (((R0)*(1.0+(PtA)*(T)+(Pt*(T)*(T)))-12.00) // ***here, add brackets also
#define PtAdVal(T,R0,Rup) (short)(1024/(Rup/PtRt(T,R0)+1))
#define PtLine(T,R0,Rup) { PtAdVal(T,R0,Rup)*OVERSAMPLENR, T },

I also increased the number of points put into the equations, because they stopped at 300, and I wanted the full 500 range.

// only few values are needed as the curve is very flat
PtLine(0,100,4700)
PtLine(50,100,4700)
PtLine(100,100,4700)
PtLine(150,100,4700)
PtLine(200,100,4700)
PtLine(250,100,4700)
PtLine(300,100,4700)
PtLine(350,100,4700)
PtLine(400,100,4700)
PtLine(450,100,4700)
PtLine(500,100,4700)

Then in Config.h I increased the max temp to to 600, just to be sure the PID overshoot near 500 will not shut off the power before it can settle.
The RTD is charted up to 700, so not worried about affecting it.

I'm also going to try the Type 20 Ultimaker PT100 table to see if it matches the OMEGA RTD.

davew_tx
So a breakout board is not required?

For what is worth, I use Permatex high temp silicone (used on engine blocs to make gaskets, the copper tube) to hold the thermistor and heat element on the head.. isolate it as well.. its easy to remove.

well, my PT100s are in the mail, and I just ran Marlin on RAMBO, with a pot resistor. The host returned temperatures as charted on the Omega chart, so I'm expecting similar results when they arrive.
Also, i like the ohm correction I added, so tuning can be done at a few points in the chart, and the offset should be the same number.

The typical Epcos 100k drops to a very similar range of resistance, in the temps we are interested in.
From the Epcos datasheet, page 40.
180.0 839.3
185.0 755.4
190.0 681.3
195.0 615.8
200.0 557.6
205.0 505.9
210.0 459.9
215.0 418.8
220.0 382.0
225.0 349.1
230.0 319.5
235.0 292.9
240.0 269.0
245.0 247.3
250.0 227.8

From the Omega PDF: OMEGA RTD

-150 39
-50 80
0 100
50 119
100 138
150 157
200 175
250 194
300 212
350 229
400 247
450 264
500 280
550 297

These are nearly identical values, and Marlin is already set up for pullup resistors included with many boards.

I think this is going to work.

Dave

Edited 2 time(s). Last edit at 05/08/2014 09:47AM by davew_tx.

I don't know how the solidoodle thermistor is placed, but when I got my E3D I wanted perfection so I put plain thermal paste to fill the hole the thermistor was in [and to increase contact between heater and block] and the temp read differences are scary. Where I would go 162 perfectly fine on my SD hotend, with the E3D upgrade I need to go at least 220C, else it won't extrude properly even at super slow speeds. I've gone to 350C just fine with the thermal paste. Heating is instant, there is absolutely no delay between pressing the heater button and the rise in detected temp. Heck, if it's just sitting there cold, as soon as I grab the hotend it shows a rise in temp. The readings are not only accurate, they're wicked fast.

Quote
MrDoctorDIV
I don't know how the solidoodle thermistor is placed, but when I got my E3D I wanted perfection so I put plain thermal paste to fill the hole the thermistor was in [and to increase contact between heater and block] and the temp read differences are scary. Where I would go 162 perfectly fine on my SD hotend, with the E3D upgrade I need to go at least 220C, else it won't extrude properly even at super slow speeds. I've gone to 350C just fine with the thermal paste. Heating is instant, there is absolutely no delay between pressing the heater button and the rise in detected temp. Heck, if it's just sitting there cold, as soon as I grab the hotend it shows a rise in temp. The readings are not only accurate, they're wicked fast.

Plain thermal paste is not rated for above 160-180C.

Ah.....