Faking sand-cast texture?

Hello all,

I’m working on a cosmetic model of a product where several of the components would be sand-cast aluminum. Some of the surfaces would be ground smooth (brushed finish), while others would retain the mold texture. Does anyone know a way of faking that sandcast texture?

Right now I’m thinking:

A) Sandcast the part in pewter- Risky, as I have no experience sand casting, and I worry that I won’t be able to get good surface detail from it.

B) SLA/SLS the part, blast it with some coarse medium, nickel plate it.

C) SLA/SLS the part, nickel plate it, apply a textured paint/coating of some kind.

D) Have a short-run foundry cast the part- Any ideas how much this would cost for a part weighing about a pound?

Depending on the complexity of your shape, a foundry might be able to sandcast directly from your RP model. There will be shrinkage of the alloy so you may want to oversize the model accordingly. There is often a part line somewhere that requires finishing and may interfere with your vision of an over sandcast look.

The machines exist for selective laser sintering of the actual sand for sandcasting, a one off part can be sandcast directly from a one off mold with no tooling. If you can find anyone offering such a service at a good cost, check the resulting part texture and see if it fits.

For pure simulation, try a textured spray paint on your model as a base for texture, the texture can be very granular, and when recoated with a silver or other color can be quite similar in texture to sandcast or tumbled sandcast parts.

For pure simulation, try a textured spray paint on your model as a base for texture, the texture can be very granular, and when recoated with a silver or other color can be quite similar in texture to sandcast or tumbled sandcast parts.

Faux Fabrix; leatherette

You might want to check out FineLine Prototyping and their “FineLine SLArmor” material. It’s a nickel plating that they can do a DSM “NanoTool” part (SLA material with ceramic in it). Maybe they could roughly sandblast the part before doing this plating process and maybe it would look and feel like a sandcasting…

Hope this helps,

~w~

I’ve enjoyed “model making” since I was kid, and it became even more interesting when it became part of my career.

“Weathering” and faux finishes are always a challenge so it’s always rewarding when you get it right. And once you have that little technique it goes into your bag of tricks.

I was heavily involved in R/C model hobby industry for many years; primarily in the manufacture of scale warship kits. Simulated dirt, oil, smoke, rust, plate lines, rivets, etc. were the crowning embellishment our customers would apply.

For giggles I airbrushed panel lines, rivets, and rust stains on my fiberglass motorcycle fairing. I don’t know how many people commented that they didn’t know anyone made a steel motorcycle fairing.

“You can fool some of the people all of the time, and all of the people some of the time, but you can not fool all of the people all of the time.” > Abraham Lincoln

But it’s fun to try, especially when you get paid for it.

You might try approaching the problem of a sand-cast texture through the back door.

To simulate the coarse texture, consider masking off all of the smooth or brushed areas and lay down a good coat of paint, then sprinkle ground up walnut shells, or maybe even pepper from a pepper mill of the right granularity to simulate the sand texture. Just dust the entire surface while the paint is still wet, and those little granules will stick to the wet areas. Then a dust on another quick but very light coat of paint to seal the surfaces. Used to use this as a non-skid surface for decks. It was fairly durable, but was like walking on sandpaper, . . .

NOTE! TEST the process first with a variety of finishes and textures until you can control the effect!!! Should work well on any SLA part.

It’s possible that SLS (laser sintering) would naturally produce the right finish, Ask for samples.

Sandcast aluminium is usually very smooth and dull, almost soft looking. Prototype-faked by a reasonably matte silver spray paint would be adequate.

Thanks for the suggestions guys! I’m leaning toward RP->blast->nickel plate because I’m not 100% confident in my ability to get a really good finish out of a rattlecan, and the finish Warren linked to looks pretty darn close to what I’m looking for. I’ll contact some shops and see what they can do.

Actual metal would also give me opportunity to use a patina or wash to bring out the texture like this:

Going straight from SLS could be good, but I think the build lines would be visible through the texture, especially once plated.

I suggest going to Home Depot (or elsewhere, I know they have it) and getting Rust-oleum high performance enamel, the Aluminum color. It looks exactly like the “FineLine SLArmor” material in Warren’s link (at least based on their small picture) and goes on really really nicely. I wish all paint went on as nicely and easily as that stuff, and it dries fast too. I would think just that paint would give you a good finish, but a light texture paint beneath it should give a nice bumpy texture. Either way you should be able to get your finish without too much hassle and expense. Metal SLS is going to be extremely expensive.

Of course, you won’t get that orange-y patina you show (straight orange spray paint would be far too even, even with the right finish), but for plain aluminum I don’t think you can go wrong with it.