Arcol.hu Hot-End v3.0.1 assembly manual - Part 4 (Mounting the power resistor)

version: v3.0.1.

Before assembly

Before you start assembly please clean the aluminium nozzle carefully with dish soap. Make sure the barrel is clear and empty before assembly.

Look down the barrel against a light source to make sure there is nothing left inside. Any aluminium chips left from manufacturing can block the nozzle:
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Screw the nozzle into the aluminium heater block, and cover the nozzle with Kapton tape, masking tape or anything else:
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This will ensure that the nozzle itself does not get any fire cement stuck to it. That way you can disassemble it later, when you want to clean the extruder or change the nozzle (eg: from 0.5mm to 0.35mm). Cover the top of the nozzle too, to avoid getting any fire cement into the nozzle. Remember that the nozzle has a really tiny opening, and any contamination can block it.
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Take a piece of A4 paper and fold it into 8 layers total:
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That makes sure you have some clearence between the nozzle and the firecement.
Here is it prepared:
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The power resistor is thicker in some parts than in others. Its diameter varies along its length, and different resistors may also have different thickness. For more information about the internals of power resistors, please see this blogpost:
http://blog.arcol.hu/?p=1718

Open a satchel of fire cement at one corner with scissors:
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The power resistor usually does not fit snugly inside the heater block (ie. if it can move around in its channel), you can apply some firecement on the side before pushing the power resistor inside
(Note: In previous instructions aluminum foil was used instead. It works great but it is timeconsuming to mount it):

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After you pushed in the power resistor, you can add thermal paste if you have (cpu paste will work). To prevent power resistor moving, you can apply more firecement on both sides:

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Get a needle and expand the little hole for the thermistor in the middle.

Now you have two possibilities. You can either let the fire cement dry by itself at room temperature for 24 hours or more. OR you can heat it up using the power resistor and 12V power source.

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If you choose the second option, the fire cement dries within 5 minutes.
But do it carefully, because if you overheat it (>280C), you can kill the thermistor.
More clarification: Dont left 12V source for 5 mins on! You are supposed to apply and reapply the 12V source to reach around 100C (when you see smoke coming off of the firecement, take off the 12V source. So you act like a temperature control circuit).
The whole process takes 5 mins, and it is not continous on! You can reach 340-380C if you left it unattended for 5 mins! It will be destroyed for sure, at that temperature thermistor gets killed, and aluminium bonds (melts, welds) together.
Also its a clever idea to apply ptfe strip onto the nozzle even at this stage too (to prevent welding together)

Until the fire cement has completely dried, the readings from the thermistor will be wrong. It may display 140-160C at room temperature. Once the nozzle has been heated up to 240C, the thermistor will report correct temperatures, as the fire cement will be completely dry.

Any 12V power source will do, polarity is not important.

Heating in progress:
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Take the previously assembled thermistor with wires:
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Put firecement on the aluminium heater one thin layer (as thin as possible, but you cant see the aluminium!), pic:
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After you let it cool down, push the thermistor into the small hole in the heater block. Be careful not to let the leads of the thermistor touch each other or make contact with the heater block. Arrange it in a way, that everything will be embedded into the firecement:
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Embed it into firecement, wip picture:
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Here are the nozzle done. Please not the well embedded wires into the firecement.
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Kapton tape removed, as you can see there is a gap between the firecement and the nozzle, so when unscreweing it wont get damaged.
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