What is the practical difference between different nozzle tip shapes?

Question

Sooooo, I'm shopping for nozzles (E3Dv6 flavor), and there seems to be several shapes available, differing mainly (or even exclusively) in the size and shape of the cone coming down to the exit orifice.

The original E3D design has a flat step with an approximately 40 deg cone sitting on top of it, the cone's diameter being roughly half of the nut size.

This design seems to be labelled by chinese manufacturers as E-V6.

The other common design is what they call T-V6, with an approximately 60 degree cone that does not end in a step but instead widens right up to the nut diameter:

And then there are variations on the theme, with some nozzles having a sharper full-width cone (also seemingly an extremely common chinese design), others having a sharper/shallower/wider/narrower stepped design, and sometimes other slightly differing shapes.

Further, there are those weird nozzles that actually have an airbrush nozzle screwed into the brass body, and ones with carbide/ruby/etc insets, which can also have either a full-cone or a stepped overall shape.

My question would be, assuming identical material, quality of fabrication, etc, how would this difference in shape affect the nozzle thermally, mechanically, and in other aspects that have a practical impact on how it actually prints? How does it affect the print settings? If I change, say, from an E-V6 to a T-V6 nozzle, would I have to change my printing temperature or retune my heater PID? Would there be a noticeable difference between a sharper and a shallower full-width cone design?

Finally, while it isn't relevant to me right now, since I included the hard-tipped nozzles for completeness, what about them? What diference does that bring? And what about that airbrush tip thingamajig?

Answer 1

The differences are mainly thermal.

Long nozzles that keep the large thermal mass as far as possible from the print are theoretically good for very small scale printing at very low speeds, where the radiant and convective heating from the block (even with silicone sock) and large part of the nozzle will tend to soften the already-printed material. Think DnD-mini scale or smaller, with 0.2 mm nozzles or finer, etc. However, you have to keep the material inside the nozzle hot all the way to the tip, and you also have to cool the printed part, so controlling exactly where the cooling airflow goes with this sort of setup is really important and precludes high airflow.

For normal-scale and high-speed printing though, you need the opposite. High air flow, untargeted, blowing over as much as possible of the recently-laid material, and thus necessarily also hitting the nozzle tip. If the nozzle is long and pointy, it has a high surface area to thermal mass ratio, and the tip will end up being a lot cooler than the heater block due to air flow, impacting rate and consistency of flow, layer adhesion, etc. Thus, nozzles that are as wide as possible until near the very tip are appealing.

Another consideration not really used in practice is clearance. A nozzle with a sharp tip allows the tool to descend somewhat below the current layer height without colliding with the print, which could be used in advanced slicing, but is not used by any general-purpose present-day (as of early 2023) slicing software.