Nozzle Selection

On my understanding the nozzle diameter it is a balance between the growing speed (per layer) and the level of desired detail. Yes, I am a beginner and I am trying to figure out how to do the correct selection for building my first Prusa. Do you have any documentation about the best practices in order to select the best size according to the required application?.
Anyway the nozzle does not look as a interchangeable part without the rest of the hot end.
I read that it is better begin with the bigger one 0.5mm; and just after doing some good jobs with that, test the smaller ones 0.35mm and 0.25mm. And they say that it is more difficult start with the smaller ones. It sound obvious because it is easier melt through a bigger hole. But that it is not related with the printing goal itself.
I have also a similar doubt about of the diameter of the filament (3mm or 1.75mm) that implies to change the extruder kit also? How to select it?
Sorry for my English (it is not my first language)

Hello and welcome,

0.5mm is a good starting point and is good for most things, you don't find much bigger sizes any more, but smaller is getting more popular.

With a 0.5mm nozzle you can be quite a bit out on flatness of the bed and also most other little things, after a layer or so it will all level itself out.
You can also use 'SKIN' in skeinforge to give you smaller layers, this will give you smooth outer walls but not provide any more horizontal detail, for that you also need a smaller nozzle.

With 0.5mm then 3mm or 1.75mm is ok, you can extruder faster with 1.75mm feedstock or use a smaller extruder motor (that also allows faster speeds = less mass moving about)

You need to select a layer height that's compatible with your nozzle, so the smaller nozzles need lower and lower layer heights, making the time to build much longer and everything starts to be more critical (temperature, moisture, hot-end design).

You will see a big difference with 0.35, but only when your machine is setup well, and at that point 1.75mm is a good idea, but not essential.

Some people are down to 0.15mm but leave that until you are a little more confident with running a RepRap.

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[richrap.blogspot.com]

I have a 0.35 mm nozzle and use 3mm filament. It produces nice high resolution prints but I can drive the bot fast when I need to (> 120 mm/sec). Moving to smaller nozzles actually helps less than you might think; most of the detail our FDM machines can achieve is determined by your layer height, which is pretty much unaffected by the nozzle size. All a smaller nozzle does is make individual layers slightly more detailed since smaller features on those layers become possible to trace without becoming indistinct blobs. But I think you'll only really start to notice the difference if you're already printing at small layer heights ( < 0.1 mm). The Ultimaker uses a 0.4 mm nozzle and produces some of the most beautiful high-resolution prints out there today, so I think it's clear that moving to a smaller nozzle isn't the biggest thing you can do if you crave more detail. You want to first dial down your layer height, and that will expose other problems that you can miss with thicker layers, such as slight misalignment between layers or temperature variations causing your extrusion width to slightly change in places.

Honestly, I'd recommend you start with a 0.35 mm nozzle and not worry about moving to a smaller one until everything else is in place to support tiny tiny layers.

I use a .35 nozzle on the Fablicator, .4mm works about equally as well. The actual nozzle diameter is what matters least in print quality, until you have an extremely well tuned machine.

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www.Fablicator.com

Thanks Richrap,

Your explanation help me a lot.
I began reading your blog; and now... I have a lot of work to do. . Congrats, What a good job!
It looks like rocket science each day. I am a little bit afraid, but a lot excited, anyway.
The nozzle diameter, is also related with the hot-tip and Heated Bed
temperatures? Changing and adjust those temperatures coordinating with Z axis displacement appears challenging also. I know, computers (and microcontrollers) can handle very complex tasks; and RepRaps are no toys, and I must grow up, act as a adult and to face the threats.
But adding some fans and ducts for cooling, make bigger the puzzle.

Thanks