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?
3D Printing Stack Exchange is a question and answer site for 3D printing enthusiasts. It only takes a minute to sign up.Sign up to join this community
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:
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:
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:
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.
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.
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.