Supports, Infill, and Not Overthinking It
Last lesson was slowing down your first layer. That's the settings that matter most. This lesson is about the two settings that make beginners overthink everything: supports and infill.
I'll save you some time. Neither one is complicated. People make it complicated.
Supports, plain and simple
Supports are scaffolding. The printer builds temporary plastic underneath any part of your model that would otherwise be printing into thin air, and you snap it off when the print's done.
Here's the rule I use: if a part of the model overhangs more than about 45 degrees from vertical, it probably needs support under it. Anything less steep than that, the printer can usually bridge it on its own, layer by layer, no problem.
Your slicer will offer to figure this out for you automatically. Turn that on. It's called something like "support enable" or "generate supports" depending on your software, and there's usually a dropdown for "support everywhere" versus "support touching build plate only." For most beginner prints, touching build plate only is what you want. That means supports only grow from the bed up, not out from the middle of your model where they're a pain to remove and leave marks on your part.
Once the supports print, you pull them off with your fingers or flush cutters. PLA snaps clean most of the time. You'll get a slightly rough patch where they were attached. Sand it if you care, ignore it if you don't.
One caution here: supports touching your part means more plastic touching your part, which means more heat concentrated in a small spot. If you're printing something with fine detail near an overhang, don't be surprised if that area looks a little melted or blobby compared to the rest. That's not a failure, that's just physics doing its thing at 4,600 feet same as anywhere else. Slow that section down if your slicer lets you adjust speed by feature.
Infill, plain and simple
Infill is the internal structure inside your part. Nothing prints fully solid unless you tell it to, because that would take forever and waste filament. Instead the slicer fills the inside with a pattern, a grid or a honeycomb usually, and you set what percentage of the inside is actually plastic versus air.
For most things you'll print in this class, 15 to 20 percent infill is plenty. That's the standard the slicer defaults to for a reason. Save higher percentages for parts that need to hold real weight or take real stress, brackets, hooks, anything load bearing. I run my garage pegboard bins around 20 percent and they've held up fine for two years.
Don't go printing everything at 100 percent infill because it feels like more is safer. It's not safer, it's just slower and it uses three or four times the filament for barely any strength gain past a certain point. I've done the math on this more than once, sitting there watching a print clock climb from three hours to eleven for no real benefit.
Where this still gets me
I'll be honest with you, because that's how I teach. Curved bases still fight me. Anything round, a cylinder, a dome, a circular base with any real diameter, likes to lift a little at first before it settles into the shape. I've read three different guides on this. I've adjusted my first layer speed, my bed adhesion settings, added a brim, all of it. It's better than it used to be. It's not solved. If you print something round and the edge lifts a hair before flattening out, you're not doing anything wrong. You're doing what I do too.
I say that so you don't sit there thinking everyone else in this class has it figured out and you don't. Nobody has all of it figured out. I've been at this a while and I still lose a little sleep over round bases.
Don't overthink it
Here's my actual opinion on this whole lesson: most beginners spend way too much time tweaking support angles and infill percentages down to the decimal before they've even printed the thing once. Print it with the defaults first. See what actually happens. Then adjust based on what you're looking at, not based on a forum post about a completely different printer.
Slow down your first layer, use the default support settings, use 15 to 20 percent infill, and print the thing. You'll learn more from one real print than from an hour of second-guessing settings you haven't tested yet.
Before next time
Pick something from your model folder with at least one overhang and print it with supports turned on and infill at 20 percent. Bring the part in, snapped supports and all, so we can look at where they pulled clean and where they didn't.