I have had many problems with my heat shrink for the thermostat on my Anet A8 melting from the heat block.

Is there a way I can insulate my wires from heat but still have enough room to put the thermistor into the block?

  • $\begingroup$ I've added another photo to my answer, that you may find very useful. $\endgroup$
    – Greenonline
    Commented May 11, 2017 at 4:05

4 Answers 4


For an illustration of how to employ the Kapton tape, that is mentioned in the answers from Harvey Lim and Howler, watch How to build a RepRap Prusa i3 (Assembly 7) at 21:30:

Kapton tape on hotend

From 15:10 the heater and thermistor is connected up, you may find this also useful. Note that, at 20:45, the heatshrink is only used over the soldered connection, and not all the way up to the heatblock:

Heatshrink on thermistor

Also, more pertinent to your printer, from Anet A8 Review – Best cheap 3D Printer?, see that the thermistor wires are also wrapped in Kapton tape in this photo:

Thermistor wires are also wrapped in Kapton tape

Note that the Kapton tape is wrapped around the wires, almost right up to the thermistor, and will be touching the heating block, when the thermistor is inserted into the hole - there is no problem of it melting, due to its high melting point.


You can use kapton tape, small PTFE tube, or silicone tape. I use PTFE on my delta printer (I do have a silicone tape wrapped around my heat block, but that's to help with keeping the heat in the block, not for eletrical insulation (although it would work for that)). These will all handle the temperatures of your heat block fairly well.

  • $\begingroup$ I was thinking about getting a custom fibre glass part made. Do you think this is worth it? Many thanks, Thomas $\endgroup$ Commented May 9, 2017 at 18:16
  • $\begingroup$ I was going to go with PTFE but it only goes up to 204C so I'm not sure now... Thanks for all the help though $\endgroup$ Commented May 16, 2017 at 16:32

You could use Kapton tape to tape the thermistor. It is usually the best option for sticking something onto the hotend or on the heat block. You will also have less trouble since it is very thin.

Note that if you use Kapton tape, you should use several layers of it for added insulation.

  • $\begingroup$ So it will not melt on the heat block? $\endgroup$ Commented May 9, 2017 at 17:26
  • $\begingroup$ Kapton should be good to 400 °C but your mileage may vary depending on where you bought it. The Ebay special Kapton may just be orange tape, who knows... $\endgroup$
    – tjb1
    Commented May 9, 2017 at 18:56
  • $\begingroup$ Well it can melt...its just no hotend on this planet could get hot enough to melt it. As @tjb1 said, it melts at 400 °C. $\endgroup$
    – Kiro
    Commented May 9, 2017 at 19:41

Ok, so I think I have found the answer. You can get cotton wraps for print heads with some Kapton tape on them, see 10Pcs 3mm Thickness 3D Printer Heating Cotton Hotend Nozzle Heat Insulation. I think this will work best as long as it doesn't catch on fire.

Please let me know if there is a better alternative but for now I will use these.


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