Question 1

What is a nozzle?

Accepted Answer

What is a nozzle?
The nozzle is the small metal tip at the end of the 3D printer.
The melted filament comes through the nozzle during 3D printing.
Compare it to the tip of a glue gun, the filament gets heated up and comes out through the nozzle. At the exact spot where the printer wants it.
What size nozzle?
A nozzle has an opening, and that opening has a size.
The most common size for 3D printers is 0.4mm. This is a standard that often comes with your 3D printer.
A smaller nozzle, like 0.2mm, prints finer but takes quite a bit longer.
A larger nozzle, like 0.6mm or 0.8mm, prints a lot faster but you get less detail.
For most people a 0.4mm nozzle is the best choice. It just works well.
What is a nozzle made of?
The cheapest nozzles are often made of brass, which works fine for common filaments like PLA and PETG.
Are you using abrasive filament, like a filament with wood particles in it?
Then your brass nozzle will wear down a lot faster. In that case a hardened steel or sintered nozzle is a better choice.
When do you replace a nozzle?
A nozzle lasts a very long time with normal use.
But it's time for a new one when:
Your print suddenly has more problems
The filament isn't coming out properly
The opening of the nozzle is larger or irregular
A new nozzle is cheap, usually a few euros.
It's actually the easiest part to replace.
Replace your nozzle when the printer is hot, otherwise the filament has cooled and hardened inside the nozzle and you won't be able to get it out.

Question 2

What is an extruder?

Accepted Answer

What is an extruder?
An extruder is the part of the 3D printer that grabs the filament and pushes it towards the nozzle.
Without the extruder the filament never reaches the nozzle and your printer does nothing.
The extruder makes sure the material ends up in the right place.
How does an extruder work?
An extruder has a small gear that grabs the filament. A motor turns this gear which slowly pushes the filament towards the nozzle.
The faster the gear turns, the more filament gets fed through.
The printer does this on its own, you don't have to do anything.
Direct drive and Bowden
There are 2 types of extruders, and the difference is where the extruder is located on the 3D printer.
Direct drive
With direct drive the extruder sits on the print head. The filament gets pushed straight into the nozzle without traveling a long distance.
This works a bit better with flexible materials, and there is less chance of problems with feeding the filament.
The downside is that the print head is often heavier, which can make the printer a bit slower.
Bowden
With Bowden the extruder is mounted to the printer frame, so not on the print head.
The filament then travels through a thin tube (the Bowden tube) towards the nozzle.
This makes your print head lighter and because of that it can often move and print faster.
The downside is that flexible materials are harder to print, and it can run into feeding problems a bit more easily.
For beginners it doesn't really matter which type you have, both work just fine with PLA.
What does the extruder do?
During 3D printing the extruder pushes filament through the nozzle.
The nozzle heats it up and makes sure it comes out liquid and lands on the print bed.
But the extruder also does the opposite, pulling filament back.
This is called "retraction", when the printer moves from one point to another without printing anything, the extruder pulls the filament back a tiny bit.
This is how the printer makes sure you don't get little blobs of filament on your print.
When does the extruder go wrong?
The most well known problem with an extruder is a clicking sound during printing.
This means the gear doesn't have a good grip on the filament and can't push it through.
This can happen because the nozzle is clogged, or the print temperature is too low.
Or even with brittle or too moist filament.
With these kinds of problems it's best to check the nozzle first, that's more often the problem than the extruder itself.
Do you ever need to replace the extruder?
Normally the extruder lasts a very long time, and replacement is rarely if ever needed.
Especially if you are printing PLA or PETG.
If you notice the filament isn't feeding properly and the nozzle doesn't seem clogged, then it might actually be broken.
In that case it might be time to replace the extruder.

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