3D printed parts look cool and unique, but sometimes you want them to look like something that isn’t 3D printed. And to achieve this, you need to cover up or smooth out the ripples caused by the FDM process.
I ran some early experiments with scratch filling primer, but it took four to five coats before getting the smooth surface I was looking for. And this took several days between wet-sanding and waiting for the parts to dry.
Not sure why I didn’t in the first place, but I remembered using automotive Glazing Putty when I customized my Jeep’s console to fit a VGA touchscreen.
To apply the putty, make sure you wear some nitrile gloves (the purple ones are cool because you’ll be like Depp’s version of Willy Wonka!). This stuff is petroleum based and will eat right through regular latex gloves and might do nasty stuff to your fingers. Anyhow… get a dab on that gloved finger and rub it into the part. Make sure to rub against the grain so that it fills in the layer gaps. If you get a little too much on at this stage, its ok… it just means you’ll have to do a bit more sanding at the next step.
Let the glaze dry for at least 20 minutes and then hit it with some 400 grit sandpaper until you see the high points of the layers coming back. Then I recommend using the previously mentioned scratch filling primer as a base layer and sanding that with a 400 grit before you apply the final color.