Ultimaker Original isolator with heat sink?

[JO3 1]

Hi, I'm having an issue that the filament was melting before it got to the heater block and causing blockage. Is there a part or a modification on the isolator that has a heat sink that stops the heat travelling backwards up the printer head?

Thanks!

[gr5 1,072]

What is your retraction distance. As long as your bowden couplings are tight and don't move up and down (as they should) then 4.5mm should be plenty. Was this print doing lots of retractions? Or did you enclose the printer when this happened? I assume this happened on PLA because not much else will melt at such a low temperature and you don't need to enclose the printer for PLA.

I never had this problem but other's have had this problem. Maybe @neotko has some ideas as he knows the UMO better than anyone I think.