Casting for Dummies

[DaKra]

For some reason I always put off casting, but I needed some repetitive parts and there was no sense in avoiding it any longer.  Just took my first baby steps and thought it might be helpful to show other timid souls how easy it really is to get started.   As easy as baking cookies, maybe easier.  Doesn't smell as nice.  Doesn't smell at all actually.  Can't comment on the taste.      For starters I made a flat back casting, which is very simple because there is no need for a two part mold.

Here is a drawing showing a wall with cast iron star turnbuckle plates or wall washers that I needed in quantity (thanks Google, I wondered what those were called!)

 

I made a few masters from plastic craft store "jewels" and commercial NBWs, and glued them into the bottom of a styrene box I made from scrap.       



Mixed and poured the RTV rubber mold glop into the box and waited.   



Result was one RTV mold



The next thing I did was mix up the casting resin according to directions and poured it into the mold.  I don't have a photo of this because it starts to set quickly.  Use your imagination here.   

This part isn't necessary, so skip to the next  if it looks intimidating.   Bubbles can be avoided in a number of ways, but I like tools and I like overkill, so I put the uncured casting into a pressure chamber at 40 PSI.  Its really just a paint pot with the paint flow tube removed and blocked, hooked up to my airbrush compressor.     The pot is rated for 80psi and has an overpressure relief valve, so its safe to use.   



Waited about 10 minutes and got this



When I trimmed the flash I had four of these.  The resin part, I mean.  Not 40 cents.



The original master is re-usable, so I can make more molds, which means I can make more castings with every pour.  And the more molds I have the more efficiently I can make castings.   

Pretty easy.  Just follow the directions that come with the rubber and resin, and use newspapers to catch the drips.     

[eTraxx]

Thanks for the heads up on that .. especially that Pressure Paint Pot. One more thing to keep an eye out for

[Chuck Doan]

Thanks for that! A casting dummy I be!

[finescalerr]

Excellent information. Worthy of publication. -- Russ

[marc_reusser]

Dave,

Thanks for the SBS. What scale are these?

Two quick tips if you don't mind.....when you get around to doing larger parts, consider placing the rtv mold back in the box, while doing the casting, as this will keep it from deforming.  This obviously can be a difficult to do if one doesn't build the rtv box perfectly square/rectalinear.....so for those that have concerns about that, you can use lego blocks, on a lego base plate, to build the casting box....that way it is also easy to open the box to remove the rtv mold, and build it back around the mold whenever you need to cast.


Marc

[DaKra]

Hey Marc,

Good idea on using the RTV box as a brace, something to keep in mind when I make bigger molds.  With these small parts in small molds, distortion isn't an issue, but I'll anticipate it with larger jobs.

Next things to try is a 2 part mold, and adding color to the resin.   

The wall washers are for a 1/87 scale model kit. 

Dave 

[mobilgas]

Thanks.....for the how to         Craig