The Ship Model Forum

I seem to remember someone posting tips on this but can't find the thread. I've used 3D printed parts on a couple of projects so far and I've now bough a 1/2400 3D printed ship.

As you probably know, the parts have some fine "slime" on them, similar to release agent on resin kits but far more persistent. In one case I soaked a 3D printed funnel in oven cleaner for a few hours then scrubbed it with an old toothbrush until my hand went numb and I STILL had trouble painting it. Now in that case it didn't matter because it was all one colour and had minimal surface detail so I just drowned it in layer after Lauer of paint until it looked OK.

But I need a more reliable technique going forward, especially if I plan to paint finer parts e.g. whole small scale ships. I have a feeling this will give me a headache otherwise.

Any tips?

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Vlad

You don’t mention which type of print, which does make a difference. I’ll assume that you’re buying the finest detail material from Shapeways, their “Frosted Ultra Detail” (or the slightly rougher “Frosted Detail”), both of which are UV-cured acrylic plastic, and specifically “Visijet SR 200” from 3DSystems, printed on a multijet machine such as a Projet 3510 HD from 3DSystems.

“Cleaning” has several aspects:

1. These parts are printed with a soft gooey support wax UNDER all overhanging part surfaces… basically the entire vertical shadow is a block of this wax. Most is washed off by Shapeways, but depending on the technician’s willingness to scrub your delicate details, much may be left behind. The stuff can be cleaned with strong solvents, but warm water and water based cleaners will do the job too. Spic’n Span, Simple Green, etc. I use a cheap ultrasonic cleaner, and follow up with pipe cleaners into any holes.

2. Wherever the wax touched your part, the part will have a frosted surface. After cleaning, this will look like a white crust of mostly parent plastic, but it seems to contain some residual wax too. I scrape/scrub/sand this, as best as I can manage.

3. This mechanical cleanup can also address any visible “print lines”, but it’s made harder for you if the designer has included a lot of integral surface details. (I prefer to make loose details for later assembly, rather than one solid and complete model).

4. Finally, paint ONLY with water based acrylics. This plastic seems to be “wet”… I don’t know if it’s uncured resin, or excess plasticizer or what, but SOMETHING in my printed parts prevents oil based enamels from curing. Water based acrylics cure just fine.


If you are trying to save $$ by buying the cheaper "Strong Flexible" material, then you are getting an "SLS" (Selective Laser Sintering) part, which is fine nylon powder fused into a solid mass. Not only do you have coarser print lines to deal with, you also have a porous sandstone-like surface to seal... AND a very tough nylon material which is near impossible to sand. Yes, layer after layer of sealing material is needed... fill with sanding sealer or primer/surfacer, and then good luck avoiding a globbed-on appearance.
I have used SLS on larger structures where I could smooth out large flat surfaces... I then populated the details with finely printed FUD parts.




FUD details on my latest 3D Printed model in 1:24 scale (cabin was made with yet another process, "stereolithography"):

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Pat Matthews
Get your boats wet!
Blog: [redacted]
Shapeways Shop: [redacted]
MWS Gallery: http://www.modelshipgallery.com/gallery/users/Pat-Matthews/user-index.html

Hi Pat,

Yes, I am using Shapeway's FUD. It's reassuring to know that it can be cleaned with household products but I'm still a bit worried because like I said, my past experience was that painting was difficult even after substantial scrubbing with fairly strong products. I will have to pay attention to this wax, but the thing is the parts feel slimy even on surfaces that are not in the "shadow" you mention. I don't see any residue on my most recent purchase at a glance.

I am also using enamel paints, always have, and I really don't want to switch to acrylics just because of this. Can you elaborate what you mean by the paint "not curing"? I had no problem with the paint drying, just the first couple of layers were very streaky as if it was interacting with something on the surface or just not sticking to it. After that though I managed to make it look OK and I had no chipping or peeling even if I put 4 or 5 layers on. Is there perhaps a primer I can use?

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Vlad

Invest in a good ultra sonic cleaner,the Airbrush Company supply a good one.

Scouse.

My experience is similar to yours, Vlad... sometimes enamel paint seemed to work, other times it simply wouldn't cure (harden)... the paint remained gooey.
We know not to apply oil based enamels over acrylic paint, just as you don't put lacquer over enamel. Maybe not the exact same mechanism- the hot lacquer solvents will dissolve enamel... but does enamel dissolve acrylic, or does something mobile in the acrylic keep the enamel from curing? Either way, it's a mess, and the 3D printed FUD acrylic parts seem to react in the same way.

Not true for all parts though... a different UV-cured acrylic resin is used in stereolithography (the process wherein a laser draws on the surface of a liquid pool of resin, curing the resin wherever it touches). The stereolith parts I have used have taken enamels happily.

Enamel primers will have no more luck on the FUD parts. Perhaps a lacquer primer followed by enamel... you'd have to experiment.

I have also complained about the acrylic paint, but have come to accept it into my shop...

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Pat Matthews
Get your boats wet!
Blog: [redacted]
Shapeways Shop: [redacted]
MWS Gallery: http://www.modelshipgallery.com/gallery/users/Pat-Matthews/user-index.html

Bestine works best on everything I've bought from Shapeways FUD plastic. Works in just 10-15 minutes of cleaning.

you sure they are UV resin? why would there be release agent on UV resin?
we do prime UV masters for casting. they can be too soft, and warp in vacuum. A thin layer of primer adds a bit of strength to surface layers.

TBH, we don't even use release agent/oil for casting resin. Good silicon rubber these days don't need that.

I've found that most of the residue disappears during the sanding (wet sanding under a faucet) to remove the printing artifacts. Denatured alcohol and a stiff brush can also remove the residue if the part has small details. Mr. Surfacer works well on FUD parts and it sticks nicely to the resin. On some parts, it's enough to greatly reduce the printing artifacts.

The nylon SLS (Strong & Flexible) is not sandable. I dangled a part in a can of auto primer overnight and let it soak up the primer. Once dry, it can be sanded to a smooth finish (basically, you're just sanding the primer).

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My Web Page

Thanks for the additional tips. Sanding is essentially out of the question since the sorts of things I would be dealing with are 1/2400 whole ships or parts for 1/700 ships e.g. bridge levels, weapons, funnels that are either thin, fragile or have surface detail.

Speaking of alcohol, would soaking it in the concentrated car anti-freeze (the one you're supposed to dilute before putting in your car) do the trick? What about Bleach?

It doesn't seem to be the case bit just for peace of mind, at any time did you have issues with solvents dissolving the part or affecting the surface?

So far on my 1/2400 Fuso I have scrubbed it with a toothbrush, scrubbed it again using strong bathroom tile cleaner, soaked it in my paint thinner (white spirit), scrubbed some more using dishwasher liquid (partly to clean off the other stuff I used) then rinsed. I've put one coat of Humbrol enamel on the deck and it seems to have gone on OK. Will need a second coat but I'll do that tonight and see how it goes.

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Vlad

Yes it is UV cured resin, and there's no release agent.

The slime in question is support wax used in Shapeway’s multijet printing process. It is soft and has a low melt temperature… the first cleaning operation uses an oven to carefully melt much of the wax off the printed part. The stuff is like bacon fat, ugh.

If you get parts from a stereolithographic printer (where a laser draws on top of a pool of liquid resin), then there is no support wax, just a lattice-like support structure printed in the parent material and which is placed under any overhangs. Then one needs to deal with the little nibs where the supports have been clipped or broken off the part.

For the stereolith parts I’ve used, there’s been no problem with enamel paints.

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Pat Matthews
Get your boats wet!
Blog: [redacted]
Shapeways Shop: [redacted]
MWS Gallery: http://www.modelshipgallery.com/gallery/users/Pat-Matthews/user-index.html

Moved this to the FAQ section, upon Tracy White's recommendation.

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Martin

"Tomorrow is the most important thing in life. Comes into us at midnight very clean. It's perfect when it arrives and it puts itself in our hands. It hopes we've learned something from yesterday." John Wayne

Ship Model Gallery

Thanks Martin, it's a good idea but it would be nice to have a sign post in the other forum for a couple of days when these moves happen.

My experience so far with my 1/2400 Fuso is that the first layer of enamel on the deck looks dry and can be touched, but scraping with any hard object will easily remove the paint. I haven't second coated it yet because I wanted to see how time affected the final curing. My options now are to strip it and try cleaning again, or put another layer on. I'm tempted to do the latter as originally planned since this is a bit of a guinea pig project.

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Vlad

Ok I've come to the conclusion, as PATMAT, that this is not a cleaning issue but something about the plastic itself that prevents enamels drying.

Now my "mission" has switched to trying to find a suitable primer. Acrylics dry fine on the part, but enamels won't cure on top of the acrylic primer either so that doesn't solve the issue. Next step, lacquer.

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Vlad

I believe you're on the right track with the primer. Vinyl figures have the same problem, enamels will never dry on them. Use lacquer and acrylics, though, and you'll be fine.

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We like our history sanitized and theme-parked and self-congratulatory, not bloody and angry and unflattering. - Jonathan Yardley