FDM print filler materials

I’m curious what materials everyone uses for smoothing out cosmetic FDM prints? I’ve seen different videos on using Minwax wood filler, Minwax wood filler thinned with acetone, Bondo glazing and spot putty, and 3M Acryl putty. But I haven’t found a good comparison of these.

I have a particular upcoming need on a print that will be painted after filler, and live outside in the elements, but it seems like any of the above would be fine for that.

I’ve not tried it but I found this process pretty compelling albeit a lot of work.

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What filament type do you want to smooth? The options vary widely with types.

Some can be hit with a heat gun set very high and moving too fast to melt the interior.

A Dremel with a sanding flap wheel is very effective too. I’ve used it to deburr the sharp stringing exit points on 0.4mm single wall petg without harming the structure.

I buy those sanding flap wheels in bulk from ali express. One of the most useful, versatile tools I own

I didn’t realize this was a technique for FDM. I had seen it for resin prints but I guess it makes sense you can also apply it to other types.

PETG and PLA. My immediate need is for PETG but was curious in general for future projects.

Dremel flap wheel sounds like a good idea, I’ll give that a try.

I really like these with one arbor and replaceable low cost wheels. There are many sellers.

In many cases you want a more rounded sander that won’t leave a mark from the far edge of the cylinder. That’s simple, just spin the flap wheel against a cinder block to take the corner off and now it’s rounded. This makes an amazingly good surface sander for curves and specifical concave dome features.

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cool! I’ve never seen those before - they look like a huge step up from the fiddly Dremel drum sander

Please wear gloves with resin. Videos like this make me cringe… Cool technique though!

Another consideration if the 3D print is intended to be an original for mold making, platinum silicone can be inhibited by UV resin that is not fully cured. This will ruin molds and waste lots of expensive silicone. If you attempt this, make sure you give the last coat a very throughout wash in solvent (alcohol or water depending on the resin). I see he coated his in primer which also works to prevent the inhibition

Living outside in the elements will eliminate the UV resin method. UV resin (resin in general) is not very UV resistant and will break down within months to years outside. I would think Bondo would be a good choice since it’s designed for vehicles that stay outside year round. Does your underlying 3D print material have the properties to live outside? PLA definitely will not hold up, especially in the summer. PETG seems to perform ok but will still become brittle over time. I haven’t tested ABS or ASA extensively.

ASA filament is ok to use outdoor in UV indefinitely without a protective paint finish.

There is a popular white gourd-shaped purple martin birdhouse whose design specifically excludes starlings from using them. They’re printed in ASA and always white to keep the interior temp under control

Wet sanding is my typical technique.