ELI5: ironing

What is ironing in 3D printing?

Ironing is when a 3D printer uses its hot nozzle to smooth out the top layer of a printed object, kind of like how you'd use a clothes iron to flatten wrinkles in a shirt [1][5]. The nozzle goes back and forth over the finished surface without actually squeezing out much plastic [5].

Why would you want to do this?

Printers can leave tiny ridges and bumps on the top of prints, so ironing helps make the surface look smoother and flatter [1]. It's like sanding down rough wood to make it nice and smooth [8].

What are the problems with ironing?

Ironing doesn't always work well and can actually cause problems like clogging your printer's nozzle because there's so much pressure pushing down [5]. Many people find it doesn't look as good as just printing the object a different way [1].

Can you control which parts get ironed?

Yes, you can tell your printer to iron only some surfaces and skip others by changing the printer settings in the software [2]. This gives you more control over which parts of your object get smoothed [2].