New hot end heater block

I made a new hot end heater block to try to increase the q (heat flow) into the melt chamber.


Reworked my hot end to remove the flange on the fitting to match a through hole in my new heater block and repaired the resistor to go into the block.  I applied high temp silicone to both leads so I could apply silver thermal paste to the resistor in the heater block without shorting the resistor.  Here is how I did that:

1) Took drill bit I used to drill out the resistor hole (just larger than the resistor maximum diameter dimension, and spiral wrapped it with masking tape along the smooth end away from the flutes with the sticky side out.  The spiral tube then slides off the drill bit.  Trim the tube with scissors to the desired length which leaves the resistor leads exposed at their ends.

2) Cut a masking tape strip to match the width of the resistor and wrap the resistor until it is just under the diameter of the inside of the spiral tape tube.  The taped resistor must slide easily inside the tube.

3) Apply silicone into one end of the tape tube to fill about a third.

4) Push resistor from silicone filled end into tape tube until the resistor is just inside the tube.

5) Start applying silicone to the opposite end to fill the tube following the resistor in as you slide the resistor in more and more.

6) Finish up when the resistor is centered in the tape tube with silicone to the trailing end, and top up the opposite end also.

7) Wait until the silicone cures.  Water vapor cured silicone can be accelerated by wrapping the tape tube resistor assembly in a damp paper towel and placing it in a warm (not hot) location.

8) After cure, gently remove the tape tube then the resistor masking.  No resistor leads should be visible between resistor and silicone plugs.

9) Voids can be filled with more silicone before touching with your hands (hand oil can reduce bond strength).

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Insert the resistor into the heater block while applying silver base thermal paste.  A little silver paste smeared into the hole bore will help the resistor slide in easier.

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One more thing- as the thermal paste has volatiles that evaporate at elevated temperatures you should provide a path for the vapors to escape for the first full temperature heating of the heater block.  Insert a dulled push pin or another resistor wire from one end into the top of the center cavity surrounding the power resistor.  I did not do this on my first run and the pressure ended up opening up a path from around the resistor to a resistor wire and allowed the thermal paste to electrify the heater block.  Apparently only one side was compromised, so it ended up not shorting out.  The other thing you could do is to mold a vent port into one side of the silicone seal.







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