Different color filament vs painting the parts

Has anyone experimented with painting 3d printed parts rather than using different color plastics? If so, with how much success? I'd prefer to be able to use different colors once in a while, but stocking a ton of filament is costly, takes space, and the plastic can potentially soak up water over time (even ABS, and bad enough to clog nozzle constantly, spoken from experience). Seems like it'd be nice to keep a bunch of spray cans (~$4-5 each, work on plastic as well as other materials so potentially useful for other projects), print parts in something like white or natural, then color them as needed.

Advantages I see:
- Cheaper, takes less space, easy to stock many varieties
- No need to change filament
- Could give the parts a smoother coat, masking the layers or other defects without need for (or in addition to) acetone vapor (if printing ABS)
- Less common filaments like HIPS, PC, etc. which often come in a single color can be colored this way
- Could easily apply many colors to one object by using masks (e.g. cellophane wrap).
- If natural is the "base" color, the rolls might keep better since dyes often attract more moisture

Disadvantages:
- More post-processing (possibly offset by lack of need to change filament)
- Once painted, ABS parts wouldn't be as easy to bond together with acetone at a later time
- Does it work?

I'm planning to test it out with some spray paint I got recently, but would be interested in any info that's already around.

Well, I usulaly do post treatment to my parts. Not only for aesthetics. The plastic can be painted pretty well. But you can use different coatings, like resins, varnishes, textured coatings, electro-coating... whatever ! The most important step in my post-prod is tumbling (I've got a vibratory tumbler at work and a barrel tumbler at home). The best is the vibratory because the barrel one is a bit too agressive on corners. But both do a great job : deburring, smoothing, and unexpected : preparing the surface for painting. When the parts are out of the tumbler, I just wash them then classic degreasing. I allow them to dry. Then you can coat them as you like without any primer. Thick resins fills any printing artefact and leave a perfect finish. I love the plasti-dip cans than leaves a smart mate finish with a nice rubber touch and feel, and speed up the painting process. Of course, the worst disavantage is time consuming. Tumbling is at last a night process and coating can take several days depending of the type of finish and the numbers of colours/varnish layers. Hard resins can take up to 48 hours to cure at 20°C. But with plasti dip, you can have a multi layer coating with previous tumbling within a day.
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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

Could you clarify what "tumbling" is in this context (can't find a definition online)? I understand it's some sort of mechanical abrasion process, but not sure what exactly.

I was actually thinking of acetone vapor smoothing my parts a bit, then sanding lightly before applying a spray paint that's also a primer to avoid the hassle of multiple coatings. That would make for a decent surface finish as well as the incorporation of color. The fundamental question being, can reasonably effortless coloring substitute for multiple-color filaments.

I mostly used my printer for fairly rough-looking parts for DIY projects (does job = pass), but I do appreciate both the aesthetic and practical, so I'd like to start learning techniques for improving the visual appearance of my parts, without stretching the budget or the clock.

Hmmm, maybe "tumbling" is not the proper word. Search "vibratory tumbler".. Basicaly it's a machine that shuffles parts in a moving abrasive media.

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

That does seem a bit time-intensive, plus the requirement for additional equipment. Perhaps I can get away with the sanding.

You're right. It's and alternative to a hand sanding and it can sands what the hand can't reach. If you don't want to sand, you must accept to see the layers, or use several coats of a thick filler which are time consuming too. For some projects, the layers lines can be a part of the esthetics. But you should at last use some paint primer prior to any paint. Coating can greatly improve your prints, but it is time consuming anyways.

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

Hello,

I am not familiar with vibratory tumbler. What king of material do you use to polish the prints? sand?

I'm actually trying to acetone vapor smooth my prints right now: ideally, that should make the layers invisible. I agree that I can't sand everywhere, but getting a tumbler is outside my budget right now. My spray paint is a paint/primer, and I successfully managed to coat some test pieces fairly well. So it looks like a valid method.

I have pained a few dozen printed items. There are many ways to do it. There is a primer filler that is made for cars that helps considerably remove the print marks as well as vapor smoothing, sanding, and spot putty are all different methods.

it seems that vibrating tumblers are not so difficult to make: DIY vibrating tumbler
I will try to make one as soon as I find a motor!