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Thing-O-Matic / MK5 Extruder: Thermal Compound

This test determines the effect of thermal compound between the resistor and the Thermal Core on the MK5 Extruder head. The setup is essentially the same as before, with cotton fabric insulation wrapped around the Core.

I applied a thin layer of Thermalloy Thermalcote II from a small bottle that I’ve had since the days when you could actually use trichloroethylene as a solvent. It’s rated to 200 °C, so it won’t last long at full throttle, but it’s not nearly as permanent as epoxy.

That’s the thin blue line around the base of the resistor. You can actually have too much of the stuff, so I applied this by rubbing a dab from a scrap of paper onto the resistor’s base and squooshing it in place.

Resistor with thermal compound

Resistor with thermal compound

The instrumentation is the same as the last time around:

Name Meter Location
TOM MK5 t-couple Top of core
T1 Fluke 52 Resistor
T2 Fluke 52 Core edge adjacent to resistor
CA Craftsman A Bottom of core
CB Craftsman B not used
MPJA MPJA meter not used

After once again wrapping the core up in cotton cloth, I skipped directly to the higher power levels and sampled the data at 20-minute intervals.

The adjusted temperature readings:

Power TOM T1 T2 CA Time Current
0 22.6 21.5 22.8 22.8 926 0.00
4 69.0 73.1 70.0 66.1 946 0.89
4 84.8 87.7 84.6 80.5 1006 0.89
4 90.0 92.6 89.5 85.5 1026 0.89
4 91.1 93.8 90.8 86.6 1046 0.89
6 114.3 119.0 114.3 108.2 1108 1.10
6 120.6 125.0 120.3 114.4 1128 1.10
6 122.7 126.7 122.2 116.0 1148 1.10

Notice that the T2 reading on the block starts out a bit higher than the T1 reading on the resistor; I didn’t wait quite long enough for the heat of my hands to settle out inside that insulating blanket.

The corresponding temperature differences:

Power R – Edge Top – Bot Edge – Top Edge – Bot R – Amb Edge – Amb
0 -1.3 -0.1 0.1 0.0 0.0 0.0
4 3.1 2.9 1.0 3.9 51.6 47.2
4 3.1 4.3 -0.2 4.1 66.2 61.8
4 3.1 4.6 -0.6 4.0 71.1 66.7
4 3.0 4.5 -0.3 4.2 72.3 68.0
6 4.6 6.0 0.1 6.1 97.5 91.6
6 4.6 6.2 -0.3 6.0 103.4 97.6
6 4.5 6.7 -0.5 6.1 105.2 99.4

And now for the long-awaited and much anticipated thermal coefficients of the insulated and greased Thermal Core:

R – Edge Top – Bot Edge – Top Edge – Bot R – Amb Edge – Amb
4 W 0.8 1.1 -0.1 1.0 18.1 17.0
6W 0.8 1.1 -0.1 1.0 17.5 16.6

The grease reduces the thermal coefficient by about 20%, although I admit the numbers going into that calculation are getting pretty close to the limits of my instrumentation. Assuming the value remains the same at 30 W, the resistors will rise about 24 °C above the Thermal Core temperature to 250 °C, their maximum rated temperature. At that temperature, remember, their maximum rated dissipation is 10% of their 25 °C value: a whopping 1 W.

The R – Ambient and Edge – Ambient coefficients show that the insulation has about the same effect as before, which is comforting.

Now, to mull all this over for a bit…

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  1. #1 by Jason Doege on 2011-01-16 - 16:03

    I think you can still get TCE as a solvent in a product called Brakleen. It is an automotive product used primarily for cleaning brake parts. However, I have always found it to be very effective as dry-cleaning fluid on natural fibers and as a means to remove “permanent” marker marks that are part of the joy of being a parent :-)

    • #2 by Ed on 2011-01-17 - 07:16

      Last time I bought Brakleen, the can touted its green makeover and it didn’t work for squat…

  2. #3 by Jason Doege on 2011-01-17 - 09:18

    Good to know. I will then lovingly and sparingly use the one remaining can I have on my shelf. :-)

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