Finishing 3D Prints: How to Sand, Fill and Prime 3D Printed Parts
We are going to be taking this incredible 3D printed red hood helmet through all the steps that you need to do to get it so it is super smooth and ready for paint.
A 3D printed helmet using a traditional fdm printing is going to have layer lines. It's just nature of the beast. It's how the FDM technology works.
Now how do we do that first thing we're going to need to do is to sand it. You are sanding plastic into a dust. It's very important to wearing a mask to avoid breathing it in.
120 Grit Sandpaper
Usually we will start out at a rougher sandpaper and then work your way up. it's how you do most sanding. I usually start at a 120. 120 does a really good job of knocking down the the layer lines and really starting to rough that up. You can wrapped the sandpaper around a sponge. It helps to have a better hold of it. The more you work, the more you'll get rid of these layer lines.
Don't forget to get into the cracks and crevices. Wrapping the sandpaper around a sponge helps you get into all those little spaces.
220 Grit Sandpaper
Use 220 grit sand paper to sanding the whole helmet all over again. Sanding takes time because you do the whole helmet or the whole prop in one grit and then over and over again the same thing.
320 Grit Sandpaper
Now we jump up to a 320. Again a finer sandpaper, a finer finish on the helmet. And again you're going to do the entire thing.
Fillable Sandable Primer
After all that sanding there are still some layer lines you can barely feel them with your nail, but they're there. So we're going to use some fillable sandable primer for that. Key thing is wash the print before you use this primer.
I like to put it in a bath of hot water for a little while. This stuff is thick that's why it's sandable and fillable and this way it breaks it up and makes for a great mix and it'll coat it really well.
Make sure you're not getting too close. Stand off as the directions say 8 to 10
inches so you're not getting any runs. and just give this a really generous couple coats. let it dry. maybe even get another coat to fill in all those layer lines.
Sandable filler primer is magic.
We need to sand this sandable fillable primer so it is smooth.
Now we're going to go ahead and give this thing a wash. I wash the print multiple times during the process to get a lot of that grit off.
If you look at this thing you can see here almost no lines now in this helmet. It's gonna have a little bit of grit. But those major lines are gone now.
Filling for Cracks and Layer Lines
Here are some of those thicker layer lines in the top of the helmet. We're going to use our glazing spot putty and a piece of foam. The foam could help to get into the cracks and crevices.
Put enough in there to fill those lines to make sure that when you sand this you don't see them. You really only want to use it when you're taking care of these really thick lines and some of the minor lines throughout the helmet. While, if you really want to get that smooth smooth surface you might go through the whole helmet.
After that i will usually have to do some filling. There are some tiny cracks or some layer lines that you couldn't get rid of. This bondo glazing putty is a really good material to use. It fills really well it sands really well. You can also use wood putty. After i use the glazing putty i'll have to sand that again.
Once the glazing compound is dry you're going to go ahead and sand. This stuff makes very fine dust. Make sure you're wearing a mask. If you can be doing outside even better.
Once we've sanded it i've given it another coat of the sandable fillable primer. Because you want to make sure you have that on there before you do your final
Little Tiny Files
As you can see some of the details are getting gummed up with all this primer.
so we're going to use some of these rasps some of these little tiny files.
Go through the crack there into the detail to get rid of that and sand it smooth again.
400 / 600 Grit Wet Sanding
Use a 400 grit then 600 grit going over all the details and this takes care of all the sanding lines. Then go ahead and wet it again and wash it down and use a 1200 grit for a final wet sand. Takes care of any sanding lines and makes this thing glass smooth.
The key thing here is you're going to wash the helmet to get all this grime off with soap and water and let it air dry. In this way it will be totally ready for paint.
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