good effort, but any smoke that goes outside the funnel entrance will never get sucked up.
Sorry , but yours wouldn't be any better than the ones that already exist with the sucker tube mounted to the iron handle.
If you do not have these big external fumes extraction horns, it is likely that some fumes will escape using iron-embedded systems. Even the weller ones do escape if you move the iron too fast.
Space, convenience and cost is important.
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2. The horn shaped extraction tube with the heater in the centre will cool the heater by the air flow, and the control of the temperature will be tricky. The flow will now depend on the angle the iron is held.
3. The wide extraction tube near the tip will interfere with visual positioning of the tip and the control (I prefer the tip to be at an angle of 30-45 degree to the board).
4. A tip that is resistant to oxidation and easily wetted (controlled) near the tip (does not need cleaning so often) will be a real nice thing. Ceramic coated tips are great! The tip should have the embedded heater.
Based on your points:
2. The heater will be more cooled, however because of the horn shape of the handle, it will be cooled more near the cold end (fan side) and less near the tip end.
3. It will interfere only if it is too big. This should not be too big eitherway, because it would be difficult to handle. If you keep the iron at a very low angle, it will interfere, but you cannot have everything, I mean either you will have precision or a long heater tip extending out of the handle. Obviously some kind of compensation must be done between openning, tip distance to the opening and air flow, in order to ensure most fumes will be sucked in without extensively cooling the heater.
The tip temperature keeping scheme has to change a bit, the tip will need more frequent pulses (due to the cooling) to be kept at the same temperature.
4. Are there really any ceramic tips nowadays? Ceramics are generally not conduct heat well. I do not know if any kind of exotic material exists. Hey why don't they make these by higly toxic Beo?
I do not try to convince anyone that this is the best scheme that solves all the problems, but this provides:
More precision to the working piece.
Coaxial fume sucking system that is believed to attract most or all of the fumes depending on air flow.
No expensive pumps are needed and the air flow can be adjusted by adjusting the fan speed.
The handle could be possibly made even 3d printed and no special heat resistant materials are needed, due to the internal cooling of the handle.
However the sucktion tube is of higher diameter. It can be made smaller, but then you lose some of the above advantages.
Also the cooling of the heater or power efficiency might be a problem (it might not).