Finishing RP Models?

Hi all,

Im currently studying for a product design degree, have spent the last year using the range of RP machines my university has at its disposal. Theyve been most beneficial to my design process on projects however after a recent trip to a degree show at another university i was struck by there much more realistic prototypes. One of the students expalined they were just finished RP models.

I have FDM, LOM and Zcorp machines at my disposal. But i believe the finished models i saw were mainly SLA models. Im interested to know if anyone has any experience with finishing RP models and whether i could finish models made on the machines availible to me.

I pressume its a proccess of priming and painting but after a web search and a search on this forum i couldnt find any info. And then im not familiar with spraying and wouldn’t know what kind of thickness to expect it to add to a part.

Any information on this topic would be much appreciated. cheers in advance.

Josh.

It’s nothing more than what you’d expect. A lot of hand finishing with sand paper to get rid of the typical stair-stepping effect, then prime and paint.

Ideally for the higehst grade appearance models you’d want to CNC them from ABS or Renshape to get the best surface quality and finish.

You should be able to finish FDM models as long as they’re thick enough - but Zcorp stuff would probably just fall apart.

Elbow Grease. A little Bondo (really little).

That’s it, the whole story. I’ve seen people try everything from Aqua Resin to coat the model, to using some kind of dip… but in reality, it’s not any faster/easier. Just like anything else, work he surface up through sanding grits, and start priming. Any really deep stair steps, fill.

Z Corp is the most difficult option. I have had some success coating with CA, and sanding it out.

For abs FDMs. brish on a couple coats of Methylene Chloride, (used to glue acrylic, PS, etc) It will harden the outer laayer of ABS solid, then you can sand and prime fairly easily. Otherwise, the ABS stings start peeling off and it’s a mess.

methylene chloride = really nasty stuff; the main ingredient in most “paint strippers.” Enters blood stream through the skin snf/or inhalation, and attacks the central nervous system, and liver tissue… suspected carcinogen.

Too bad it is so effective.

Nitrile gloves (2 pair), well ventilated area, and saftey glasses.

No cheating.

METHYLENE CHLORIDE MSDS: Avantor is setting science in motion for a better world | Avantor

if you need guidance on getting superb finishes with spray painting, wet sanding, etc. check out car finishing sites. I found a great collection of tips and tricks at http://www.hotrodders.com/kb/body-exterior-articles… you can skip past the articles on detailing your hood ornaments.

Thanks for all the responses, its been really interesting. is there an alternative to the rather dangerous looking chemical? would primer do a suitable job with enough sanding? I need to think of something to model to try all this out, think i will reverse model an existing project and try finish it. if all goes well i will take a picture or two so you can give me some feedback :stuck_out_tongue: lastly what kind of paint should i be using? any suggestions on a brand or retailer?

Cheers again, really keen to try this out!

JT, with regard to materials/suppliers, are you in the U.S.?

JT pictures would be a good idea, so we can better get an idea of what your trying to achieve. Just to clarify you are asking what is the best way to finish RP only, or are you asking how to make the best models? Often when model making I cast the parts in RTV material, It gives you and array of materials available… such as transparent or softer rubber materials. Tell us more info :slight_smile:

My school has a zcorp machine and I actually love it for finished models. Take a model straight out of the machine and sand it VERY carefully to get rid of the stair steps, then dilute some fiberglass resin with acetone and spread it on in 3 or 4 thin coats. Because it is thinned, it seeps into the pores rather than just globbing on. It ends up quite strong and quite smooth. then just a little more sanding, prime and paint. I always use auto body paints and a “sandable primer”, it is a thicker primer to fill any tiny holes. You can get spray paint cans of it for cheap at any autozone, checker, schucks, or whatever.

We have an FDM printer & I have found that floating a thin surface of body filler or glazing putty with a bondo spatula works well. Apply the filler just enough to fill in the steps, then wet sand it smooth with 400 or 600 grit sandpaper. Then prime, paint and dazzle!

with regards to suppliers im in the UK.

Answering Earthmans question, im more interested in finishing the rp models as im currently making unfinished models using them. However im keen to learn new things so feel free to expand on the RTV stuff if you fancy it :slight_smile: Currently have a Zcorp model sitting on my desk of my current project and the stepping is a lot less severve than with the FDM components. I guess that means a bit less efforts needed to get a smooth surface finish. Am i right in saying bondo is quite a thick putty like material?

Josh.

JD, basically its a game of what works When I ran my first Zcorp model I used cyanoacrylic (super glue), but that gets expensive quick. What I did was print small test tiles and tried different materials, I made the tiles an upside down 7 so I could see if dipping made some materials run. I remember I used spar varnish for one Zcorps project because that was all I had and need to get it done quick :slight_smile: . Zcorps prints will suck up material pretty well, they’re just a pain to finish, especially small detail. I like themonet suggestion about trying thinned resin. If you want to try RTV molding PM me I’ll send you some info… maybe you can get free samples
Good Luck!

Here’s my formula for finishing Zcorp prints

  1. Quick sanding to remove really high spots - but leave some ridges for yourself be able to tell when your at your CAD surface (you don’t want to sand too much off)

  2. Wear a mask while dripping some water-thin CA (ZAP works) onto the surface. you want to do this slowly because the reaction that happens will cause heat\ warping in thin walls if you move too quickly.

  3. Once the entire surface has been hardened and has cooled (done reacting) shoot it with some good filler primer (evercoat is the best). After drying another sanding to sand down the ridges - use the ridges as a guide coat to see when you’ve made it down to an even surface.

  4. Use glazing putty to fill in any cracks\ pits\ remaining ridges - this stuff is great but you have to apply it very thin and quickly - also you’re doing this in a well ventilated are - same place you would paint.

  5. Sand from 220 - 600 - more surfacer then continue with wet sanding till you’re happy with the finish -

then final paint
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I have been doing the same thing for this motorcycle concept which i’ll add to my thread over in the projects section. I got it SLSed, and it initially had quite a rough surface finish. I bought white primer, VW Mars Red auto paint, and a variety of different sandpaper grades. All from Halfords, except the sandpaper from B&Q.

I did a LOT of thin coats with the primer, with dry then wet sanding between. After I had it nearly to the surface finish I wanted, I painted it red, again with more wet and dry between coats. I think it ended up with maybe 8 coats of primer, and 4 coats red. I finished off with one quick coat of clear gloss - lacquer i think. I did lose some detail with the painting, but it was a quite small part. In between coats I did kind of scrape excess paint out of parts and also had to sand off globs of overspray.

To spray it all, I actually ended stringing it from the ceiling in the cellar so I could get to it from all angles and so it didn’t have to rest on anything.

Photos soon.