Working with resin / 3D printed parts

[RocketFoot]

So I bought some resin parts such as an engine kit and some 2 piece wheels.  I'm looking for some tips on painting and assembling these parts...specifically, WHEN to paint?  Should I assemble the parts first?  Like the wheels, they are 2 parts wheel sets that have a spoke part and then a outside ring that varies in size for offset options.  Would you glue the ring to the wheel first and then paint or paint first and then glue?  Same question for engine parts...I will be painting several of the parts different colors and it would be easier to paint them before assembling but then I have to worry about messing up the paint while gluing them together? 

Sorry for the questions...I am very new to painting and air brushing and not familiar with all the tips, tricks and etiquette!

[espo]

I'm fairly new at using printed body parts myself. One thing I would suggest is a lot of sanding as part of the body prep. What I have found is that often there will be very fine lines on a flat or curved printed body part.  These will not always show up under a light coat of gray primer. My thought is that a flat paint finish does not show these lines the way a gloss finish does. After a first or even a second coat of the gloss color they start to show when looking at the part at an angle. My suggestion would be to first sand the part going to even a finer level than normally done before premiering. Next apply a coat of whatever gloss finish you are going to use or even a light coat of gloss clear just enough to get a shiny surface if you're going to do a multi laired candy or pearl color. Then a light sanding with a 2000 or higher sanding cloth should reveal any under lying lines still on the part. I also think that starting with a higher fill type primer may help fill these very fine lines to begin with.  

[Oldriginal86]

I haven’t used any 3D printed body parts but have built several engines. Depending on the vendor, there may be print lines in the part. Several coats of primer and sanding sessions should take care of all but the most severe lines. Choose the vendor carefully. The better the print, less work. No difference in painting and assembling printed parts versus plastic kit parts other than the glue. CA adhesive and accelerator works well. The paint was just Testors bottle paint either airbrushed or brushed on. No issue with paint drying other then silver.

[stitchdup]

I would use automotive filler primer when preparing the bodies, and i hold the can low to the part I'm painting so more paint catches in the print lines. It makes priming take longer as you can only do one direction at a time but it saves on paint and sanding. If there trim or detail you want to save mask it off before priming and then dust it with ordinary primer after the main bodywork is comlete. Then its just paint as normal

[bobss396]

I'm doing a 3D printed engine now, just getting into the prep part. Lots of tiny pieces to contend with. Most I was able to drill a small hole (won't show on assembly) so I can spike them on a toothpick. Others I will have to hold with fun-tack.

Choose vendors wisely for sure. I just did a couple of disc brake assemblies from one vendor, the rotors were way too thick, lots of labor on my part. I tried another set from someone else, like night and day.

I have some parts from VCG Resins that require almost zero prep. I can go right to a top coat without primer. On things with post-finish assembly concerns, I'll drill them for small pins, so the parts register well for assembly. Less chance of messing them up. I have yet to have to strip a printed part after it was painted.

[MeatMan]

Before doing any painting make sure you test fit everything. Sometimes there are inconsistencies between parts while printing or casting.
As for painting, I'd paint anything that's a different color before assembly if you're airbrushing, and especially the wheels if the centers are one color and the rim chrome or aluminum.

Enjoy!

[Brizio]

Not knowing the engine you have, some parts can be glued together before primer and paint. Some it is easy to prep and paint them separately. 
Same with the wheels. if you glue them, they are going to fit the tire? Of is better glue them directly on the tire?

Maybe post a photo so we can give you more info.