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I see hotends made from a lot of different materials. Most tips are brass, while the tip/heater/sensor holders are made of aluminum, or stainless steel.

Wouldn't it make more sense to use something with a higher thermal conductivity for the heater/sensor holder, like Copper? C110 Copper is as cheap or cheaper than Brass.

Then I see hotends with cooling fins to keep the heat away from the incoming filament. But they use a thermal conductive material there to be able to dump the heat. Why dump the heat? keep it concentrated in the tip. It seems to me that we're wasting heat. We throw more power at the tip to melt faster to make builds faster, but we dump so much heat.

Why not use a non-thermally conductive material to hold the tip/heater/sensor? Yes this does start to move out of being able to machine a piece of commonly available metal to a different type of material. But with a 3D printer you could print a mold for any anything that could be poured into a mold, dried, and possible fired. Nijna Flex TPE comes to mind for making a mold. Just about any mold-able material can have it's thermal conductivity reduced by adding glass microballons. (I've thought about those in a filament to make it thinker... carbon fiber, and glass microballons... hmm.)

Or why not just coat the whole hot in exhaust ceramic powder for exhaust systems and bake it on. At least you can keep come heat in...

So am I just way over engineering?

I don't think you are over engineering at all. The Companies want to make them as inexpensively as possible and sell them for as much as they can get.
Your type of hotend would be great but the manufacturing costs go up, the sell price goes up and they would not sell as many, that is basically why they
don't manufacturer them.

I think your last idea is the best idea.

I think it's more about availability of materials and cost that brass ends were used. I'm not sure about which is softer. Of course, copper is more conductive but the difference isn't significant for these purposes.

Isolating heat - to avoid creep is the big thing. There are loads of new hot ends coming out to take on the heat containment issue but your idea about a ceramic coating is very interesting. The thing is that tips are only about $15 and in the SeeMeCNC design, they're cheap to replace.

The bigger opportunity with heat is on the heated bed. It would be fantastic to have a hot end that only heats up in certain zones - and it has been suggested before.

Max wrote: Then I see hotends with cooling fins to keep the heat away from the incoming filament. But they use a thermal conductive material there to be able to dump the heat. Why dump the heat? keep it concentrated in the tip. It seems to me that we're wasting heat. We throw more power at the tip to melt faster to make builds faster, but we dump so much heat.

Here's my guess as to why:

1) The only way you can keep heat concentrated is by insulation. Entropy is a harsh mistress.
2) You need a smooth uninterrupted path for the filament to go through up until it hits that hot zone. For ease of manufacturing, right now that means something threaded, which means something metal, at least if you want to be able to get your hot end up over 240C. That means we have to dissipate heat. We reduce the conduction by having a small cross-sectional area through the heat break, and then fins/fan to radiate it off.

So, to avoid active cooling above your heater block, you need a material which can withstand 300C at least, is easy to manufacture on small/moderate scale (no one in the 3d printing world is 'large-scale' in manufacturing), and is not thermally conductive over the time period of a large multi-hour print. (keeping "some heat in" isn't going to be good enough when dealing with PLA)