Another heater overrun

Vertex 3D Printer Vertex - Issues while printing
1

I just finished assembling my Vertex K8400. I was loading PLA on head 1 (right) and the print head was getting hot enough to melt the print head housing. Tried the other side (left ext) and got the same result. I probed the head (as best I could) and the thermometer shows 300 degrees celsius, while the display shows 190-210. Of course the PLA is bubbling and spitting out of the print head because its so hot.

Any thoughts on what I should check/test. Here is what I’ve done so far:

Probed both thermal resistors I get 6.3K ohm. - This would lead me to believe that the thermal resistors are bad. I read in another thread they are supposed to be 100K ohm when cold. But both of them at the same time?

I’ve run both extruders independently (just the load cycle) and I get the same result from both.

Since the insulator housing has melted, do I need to replace them? They have sagged towards the build plate, but I could push them back up and let them cool.

Any advice would be greatly appreciated.

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[quote=“carmath”]Probed both thermal resistors I get 6.3K ohm. - This would lead me to believe that the thermal resistors are bad. I read in another thread they are supposed to be 100K ohm when cold. But both of them at the same time?[/quote]The correct value is indeed 100K. You must check the value with the thermistor wires removed from the terminals. And check that the thermistors are correctly positioned in the holes (if they’re even a bit outside they won’t give a correct temperature.

[quote=“carmath”]Since the insulator housing has melted, do I need to replace them? They have sagged towards the build plate, but I could push them back up and let them cool.[/quote]You must replace them as they must be of the correct length and perfectly straight.

If the value of both thermistors is 6.3K then they’re faulty and you should open a ticket on the Velleman support and explain your issue.