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Old 12-24-2018, 04:26 PM
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blackshire blackshire is offline
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Join Date: Jan 2009
Location: Fairbanks, Alaska
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Quote:
Originally Posted by teflonrocketry1
For Gluing ABS to ABS I have been using Testors Plastic Cement containing MEK. I use it to glue 3D printed ABS parts together, I let them set up or dry overnight. I did this for my Estes MX missile clone and later accidently droped it on the floor; the glue joints held up nicely but the thin ABS fins on the fin can didn't.

For gluing these 3D printed ABS parts to paper tubes I use tube type plastic cement and rough up the plastic up with coarse sandpaper. ABS is very similar to polystyrene and the techniques I use for gluing and finishing them are virtually the same. ABS is short for Acrylonitrile Butadiene Styrene it is a copolymer of styrene, acrylonitrile and polybutadiene. Typically around 50% styrene 30% acrylonitrile, and 20% butadiene, these amounts can vary depending on the characteristics of the plastic. Expxy and CA glues also work on 3D printed ABS. I should mention that I am a professional chemsit by training.

[A] For 3D printed ABS I sand down the corduroy finish with 220 grit sand paper followed by 400 grit and then apply Rust-Oleum Light Gray Automotive primer (#2081). If I am using the bare plastic as the exterior of a model I sand with 600 grit then 1200 grit and do a final polish with automotive scratch remover or whintening toothpaste on a clean cotton cloth. I then sometimes coat the plastic part with Krylon Crystal Clear Acryic spray paint (#89116).

[B] I have a huge indoor ventilated pinting booth and I only spray paint my models. I apply a heavy coat (slightly runny to almost dripping) of gray automotive primer over 3D printed ABS parts, polystyrene parts, bare deep grained balsa and basswood as well as over Estes textured paper body tubes with deep spiral grooves. I don't use sanding sealer anymore since the automotive primer works so well. I let this coat dry for over 48 hours then sand it back with 220 grit followed by 400 grit until the original surfaces just start to appear or show through. If you try to sand the primer coat in less than 48 hours the sandpaper will clog and you will not get good results. Next I recoat the entire models surface with Rust-Oleum American Accents Flat white primer (#327914). If I need to preserve fine details in the 3D printed or other plastic parts, wood carvings or paper embossings, I wil forgo the heay coat of gray automotive primer and use only a thin coat of the white primer. I wait 48 hours and then sand this coat with 400 grit paper. If there is a gray colored primer coat below this white primer it is eay to tell when you are sanding too far down into the previous base coat. I have had issues of CA glues causing both enamels and laquers to craze and wrinkle over the areas where they were applied even through a thick coats of primers!

[C] I only use brush paint for fine detail work and touch ups. The ring on the upper part of my Red Nova nosecone see http://forums.rocketshoppe.com/show...645&postcount=7 was hand pinted using a very fine nylon brush and Testors enamel paint. I sometimes use acrylic paints over the white primer mentioned above. I did this on the nosecone for my FlisKits Nantucket Sound (see attached) but I couldn't get as smooth of a surface as I do with enamels and lacquers. An overcoat of Krylon Crystal Clear Acrylic helps hide the brush strokes and other blemishes in the acrylic paint. My friend Andrew swears by Testors Acrylic paints and uses them on the exterior of his models. He gets a nice smooth finish; he is also a professional painter by trade, but he tells me its the paint not the painter!

[D] The Krylon crystal clear works great over acrylic paint, enamels, lacquers, home made inkjet decals and 3D printed ABS, but it is not compatible with some markers and silk screened decals; it causes the makers to run and the silk screen decals to warp and move. I use Future Floor Wax (FFW, now Pledge with Future Shine) over silk screened decal sets, enamel, acrylic, laquer paints and 3D printed ABS plastic. I apply full strength with a foam brush over an entire model. I have also used FFW in an air brush to spray it over small areas less than 2 inches square; you can thin it with water if desired. This clear finish can be removed with ammonia water and is compatible with all the above except water colors and washable markers.

[E] ABS is mostly styrene and I have yet to see anything different from the behavior of styrene itself; if it works on styrene it will also work on ABS. Most of the plastic nosecones Estes makes are thin polystyrene. That said there are still the general rules of painting like never put a laquer over an enamel finish or you will get alligatoring and crazing. Laquers dry smooth in about 15 minutes , enamels take at least overnight to dry to touch. Laquers are sensitive to moisture and humidity and never should be applied in over 70% humidity unless you are going for the fish-eye surface look in your top coat. I aways wait 48 hours or more before applying another coat over any paint; this was a hard learned lession. I always let the clear acrylic coat cure for at least 48 hours over my home made decals before I attempt to use them. I find the under coat of the flat white (and/or gray) primer which likes to go on the surface as a nice thin film helps to preserve the plastic parts and keep them from crazing even after application of a laquer.

I have also found the new Krylon white primer (#3455) is unsuitable for use as a primer under anything, I am not sure why Krylon even relaesed this new formulation; everything I have apllied over it wrinkles and crazes. Krylon laquers used to be my prefered spray paint, but with the formulation changes I now almost soley use Rust-Oleum enamels.
Thank you for posting this detailed guide for gluing and painting the different 3D printed *and* Estes-used plastics, Bruce! Formulations have indeed changed (and new paints have appeared) since I last worked with them. (You could probably also 3D print formulation- and shape-optimized hybrid motor fuel grains [and propellant grains, too, if you could make it in filaments wound onto spools and 3D print the grains at low enough temperatures to avoid self-ignition :-) ])
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