Heater block materials, shape, heater & sensor position
Before the last burn had healed I have given myself another one, looks like it's going to blister too.
I have been printing in Vanilla White PETG (great match for retro computer cases) but this roll seems to have been cursed; it must have been a blocked nozzle (though it had multiple cold pulls to try and clear it between print attempts) but it was starting a job perfectly and then failing after four hours or so, click, click, click! Switching to a different .4mm nozzle seems to have fixed it but now I have a leak from the top of the block.
Anyway in removing the nozzle and performing many, many clearings of the PTFE tube some questions came up about the heater block.
- why aluminium and not copper? Is it important to keep the mass of the extruder low? Copper would be more durable. Conducts heat far better. Very likely more expensive though.
- why are the heater and temperature sensor where they are? Their position makes holding the block with an adjustable wrench while trying to unscrew a tight and hot nozzle very difficult. There is little room and the wrench is dangerously close to the delicate wires. Could these be inserted from the rear of the block? I understand the arrangement is heater-nozzle-sensor so that when the sensor reads a temperature the nozzle is at least that hot. But the nozzle could still be placed between the two inserted from the rear, leaving the sides of the block unobstructed.
- why not remove the need to hold the block with a wrench? Instead have a threaded hole for a tool that could screw into the front of the block and make holding it while hot much easier. A simple M5 bolt with an insulating wooden handle would do for starters.
- when you have a leak from the top of the block it's a mess. Also I have that .4mm nozzle that keeps clogging. Is there a way to chemically clean PETG? Is Methylene Chloride a solvent or only useful as a welding glue? I am wary of more burns trying to clean it while hot and don't think I will be able to completely clean the thread above the nozzle that way.