3D printing nozzle characteristics

Nozzle shapes and nozzle materials

Obviously the nozzle diameter is one of the major parameters when 3D printing. But you may have wondered about the many nozzle shapes that are available on the market. Some brands have preferred shapes. And, even though will not have a drastic impact on the print, they may be significant and worth a post.

Overall length of the nozzle?

Marketbot vs Ultimaker nozzles.
Both are quite long, but the former has a
bigger flat ring around the nozzle hole.

In my opinion, long nozzles are more convenient for cleaning, and they let more cooling air flow around.

Shorter nozzles reduce heat loss a bit and they probably give a better control and reading of the temperature (remember: the sensor is on the heating block, not on the output).
They could arguably help to reduce the overall length of the hot end, so they reduce could positioning error slightly. And they may spare a few grams... But this is marginal and for the most hard core players: they will not help make a bad design better!

Cooling 3D prints with an aquarium pump

3D printing cooled with an aquarium pump!
It works well and it cannot be quieter. The pump is bulky,
but the overall is a very compact hot end.
(the above was a preliminary experiment)

Interestingly, while this trick is not new, very few people seem to use it. For years I had an air pump on a shelf for this purpose. Only recently did I use it, and I really like it better than fan on the hot end.

The good thing is that aquarium pumps do build some pressure in order to pump air down into water. No regular radial or axial fan can do this, they only move air around. Do not get me wrong: regular fans works well, but the smaller the fan the noisier and the shorter its lifespan. And they are bulky anyhow and obstruct the view.

Actually, I printed almost years without fans attached to the hot end at all. Instead, I used a large, powerful and silent 120mm PC fan on the printer chassis. It blows a lot of air on the whole part, which is often even better, but it fails to cool down tiny towers or islands when the hot end never move aside (flowing air is very lazy and will not reach tortuous parts). Also, the big fan blows air only from one direction, which shows up on opposite sides.

So I still needed air again on the head....

E3D v6 hot end: ideas and assembly tricks

Assembled E3D v6 with a few particularities

You may remember that I wrote broadly about hot ends in an another post, but this short new one is specifically about the sixth revision of the E3D family (E3Dv6).

This is probably the best hot end on the market right now (in my opinion -- and I did not check them all). It is not cheap, hence expensive as all the good quality hot ends. But this is a critical part where you cannot really lose money if you value your time...

However there are still some room for some improvements. 

Thoughts and hints around hot ends

This post finally documents ideas and hints I had during the design of two hot ends I made last year.

My extremely small "cheesy hot end" (all-metal and actively-cooled), here with an Ultimaker printed support.
This hot end was very easy to make (only used basic tools) and also because the barrel is quite short.

At the time I already had ordered an E3D hot end, but the lead time was so big that I decided to give it try myself. Actually, since I attached it with this tiny E3D support on my Ultimaker, I almost never swapped my hot ends anymore because it is just so reliable... The only drawback is that the efficient heatsink could be made almost half the size for more Z space, less vibrations and less weight (hence my smaller, low cost --and low quality-- copycat by the way, see below). And it does not mean I stop thinking ;)

Robust bowden attachment with a blind rivet nut

Using a blind rivet nut to fix the bowden tube once for all

Blind rivets nuts give you a nut where you cannot reach the other side of the support.

Presenting my eBay Ultimaker clone (part 2): the head

An improved hot head that looked like an official V2

You may want to check also the first part.

To the credit of my seller, the printer came with a few special improvements from the real machine. To his discredit though, freely using the name Ultimaker is illegal, and I am far from sure that he released these modifications under an open hardware licence, as required by the initial designers of the Ultimaker. As a general rule, consider also that your free support should come from your seller and especially not from the company that got abused in the first place!

Isolate the hot end with Kapton and fight plastic leaks

Simply use kapton on your hot end !

My head came pre-assembled but it had a small leak between the Peek isolation and the aluminium heating block, that appeared at high temperatures. This resulted in oxydized PLA liquid (the brown juice that becomes crusty when cold), and it dropped on my prints, leaving a dirty dark trace in the object.

I first wrapped the peek and heating element with aIn any case I see no reason to do otherwise now. paper towel. But I had to change it often, and it becomes so dry that I was fearing it could start burning with the smallest trigger. But the leak finally reduced on its own.

Filament plug, hot head and the short bowden tube

Get rid of a plastic plug in an early Ultimaker V2-like hot end

Updated: check my alternate blind rivet nut setup, it is way more robust.

Shortly after I changed the small bowden tube between the two plates of my V2-like hot end, I made the mistake to cut it a bit too short. Well, I did not try to find a place that would specify this the length, given that my head was not designed by Ultimaker in the first place -- I think.