MK5 Extruder: Thermal Riser Temperatures 2

Switch block - top
Switch block - top

Using pretty much the same setup as before, I put the Thermal Switch Block at the top of the MK5 Thermal Riser Tube and the little heatsink at the bottom. The heatsink sat between the bolt head and left just enough room that I could snake the thermocouple bead into the brass tube, so these temperatures should be much more representative of the actual Thermal Riser.

After getting everything stuck together, I discovered that I’d interchanged the thermocouple leads. Rather than fixing that, take note that the T1 and T2 datasets represent different objects, but the same physical position: T1 on the bottom, T2 on the top.

I skipped the staged warmup, cried “Fire the Thing-O-Matic!” and ran it to 225 °C while recording temperatures every 5 minutes along the way. The graph looks like this:

Thermal Riser Tube Temperature Graph - block on top
Thermal Riser Tube Temperature Graph - block on top

They’re not quite exponentials, because the Core temperature gets flattened at the top, but they’re still pretty.

The top-to-bottom temperature differential has increased to 35 °C, although the top temperature still hits 90 °C. I think there are countervailing forces at work:

  • The thermocouple is in better contact with the Heatsink: the bottom of the tube really is hotter with the Heatsink at that end.
  • The Thermal Block gives a better measure of the top-of-Tube temperature, because that thermocouple is intimately connected to the Block. The Tube top is about the same temperature, but the previous Heatsink temperatures were lower.

In short, I trust these readings a bit more than the previous ones.

But, as before, the Switch Block is still too hot for a 100 °C Thermal Switch. The next step is to add a somewhat larger heatsink from my Parts Heap and see what happens.

The original data:

Thermal Riser Temperatures - block at top
Thermal Riser Temperatures - block at top