Dudes about thermal paste....



  • Hi,

    I recently ran out of the thermal paste that came with the hotend, and after cleaning, I had to put another. What I have found in a local computer distributor is the thermal paste that is put in the union of the processors with the fan, to improve heat transfer ...

    Coinciding with that moment, I am having jam problems, they are almost always in the heatbreak, so I am not sure, that the thermal paste I am using is adequate.

    The thermal paste that is placed in the heatbreak, which function has:

    A- Improve the transmission of heat from the heater block to the hotend, so that heatsking can dissipate the heat ... in that case the thermal paste is adequate. Do not?

    B- Make a barrier and prevent heat from rising to heat sking so that the filament arrives as rigid as possible to the hotend ... is that case, I'm afraid it is, I am using a thermal paste that is NOT, since it would have To put the opposite, a thermal paste, which will prevent heat from rising ... If this is the case, what type of thermal paste should I use? brand?

    Thank you



  • Something as basic as this should do. White silicone heat paste.

    https://www.amazon.com/dp/B002NLUX38/ref=psdc_2998409011_t3_B00VLQX7VQ


  • administrators

    Thermal paste is used between the heat break and the heatsink, to improve cooling of the upper section of the heat break. The type of thermal paste used with CPUs and other semiconductors is suitable.

    This type of thermal paste is not suitable for high temperatures, so it should not be used between the heater block and the nozzle or heat break. Some people use copper grease in that position.



  • It is possible your jams are from having no paste.

    However... I've used hot ends with and without paste and never seen that much difference. Look at other causes as well.



  • @Danal hi, think... I have a posible cause... Days ago, o have changed heat cardrige, from 24v 40w to 24v 50w...and i dont know what its the reason, but with this heat cardrige 50w, the heat rises to heat skin, how if the fan cant disipate de heat....

    Think



  • @peirof , hopefully you ran an auto calibration routine ?
    I also run my 50W heaters at 80 % PWM.



  • @dc42 I've read that copper grease is a really bad idea in conjunction with aluminium as they'll form a galvanic cell. This apparently leads to seizing and galling.
    I never tried it for myself, just wanted to throw it in there ☺


  • administrators

    @Eumldeuml said in Dudes about thermal paste....:

    @dc42 I've read that copper grease is a really bad idea in conjunction with aluminium as they'll form a galvanic cell. This apparently leads to seizing and galling.
    I never tried it for myself, just wanted to throw it in there ☺

    That sounds entirely plausible to me.



  • @dc42 I use antiseize compound from an auto parts store- it is commonly put on the steel threads of spark plugs before installing them in aluminum engine blocks. In a hot-end heater block, the greasy part of the stuff burns up and smokes for a few seconds the first time it gets hot, but it works well. I think the stuff is some sort of high temperature grease or maybe wax mixed with a high percentage of graphite. I put a little of it on the nozzle and the heat break threads.



  • I would imagine that computer thermal paste is not up to the task. Arctic Silver 5 http://www.arcticsilver.com/as5.htm is one of the best, and it's temperature limits are:
    Extended Temperature Limits:
    Peak: –50°C to >180°C
    Long-Term: –50°C to 130°C
    It'll be breaking down, possibly burning, maybe leaking.

    Ian



  • @droftarts said in Dudes about thermal paste....:

    I would imagine that computer thermal paste is not up to the task. Arctic Silver 5 http://www.arcticsilver.com/as5.htm is one of the best, and it's temperature limits are:
    Extended Temperature Limits:
    Peak: –50°C to >180°C
    Long-Term: –50°C to 130°C
    It'll be breaking down, possibly burning, maybe leaking.

    Ian

    It is up to the task, because you only apply thermal paste on the cold side of the heat break and this side never reaches over ~80C



  • Thermal paste is a very bad heat conductor: aluminium is 240 W·m⁻¹·K⁻¹, good thermal paste is... 3 W·m⁻¹·K⁻¹!!! 2 orders of magnitude less!

    It should only be used to fill tiny little air gaps, remaining after polishing surfaces. On processors, the best way is to have very flat/polished surfaces, and apply strong pressure. Thermal paste should be put in a very thin layer.

    I often see people putting way too much paste, reducing the heat conductivity instead of improving it! I never put thermal paste or grease in any hotend, and never had any jam issues.



  • I use (and Slice Engineering recomends) Boron Nitride paste with the Mosquito Hotend; I have personally applied it to the thermistor and heater cartridges, although they have some additional application insight listed on their website:

    Slice Engineering™ recommends Boron Nitride Paste for use in hotends of any brand. For
    decades it has been used as a “heat transfer and release coating” for industrial cartridge
    heaters. Use it to improve heat transfer:
        ● From the cartridge heater to the hot block, to extend the life of the cartridge heater
        ● From the hot block to the temperature sensor, to shorten response time and improve
           accuracy of temperature measurements
        ● From the hot block to the heat break to improve high flow rate performance when
           printing with large diameter nozzles
        ● To improve the seal between nozzle and heat break
    
    Boron Nitride Paste may be used generally, in assemblies operating in temperatures up to
    1000°C, as an electrically insulative heat transfer and anti-seize compound.
    

    Listed thermal conductivity of 31.4 W/mK


  • administrators

    Boron nitride (hexagonal) is good stuff, I used to make waveguide CO2 lasers out of it. Few other materials have such good thermal conductivity yet are electrical insulators.



  • Agreed on the utility of boron nitride paste. I also use it on the threads of the nozzle in my Mosquito hot end and it ensures that removing the nozzle is pain free every time.

    I can't quantify it, but it feels like it has also made steel nozzles a little less reluctant to getting up to temperature and staying there.

    The only thing to watch out for is if there's any excess at the ends of the holes for the heater cartridge and temperature sensor, it tends to fall off and get incorporated into whatever you're printing at the time!


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