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First casting project, looking for materials advice

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First casting project, looking for materials advice

Postby Jack.Straw » Mon Sep 14, 2015 12:54 am

Hello. I'm making plans to embark on my first casting project. I would like to make a night-time version of my favorite yard game, Kubb. The idea is to cast translucent versions of all the pieces pictured below (i did make those pieces, mahogany & maple), each with a thin channel in the center where a glow stick can be inserted. I've been watching videos and reading online about a lot of different types of resins but am still unclear on which would best suit my project.

Image

I guess the biggest concern, and something that none of the tutorials seem to address, is impact durability. The nature of Kubb is to toss the long baton pieces and knock over the short pieces (the kubbs), and eventually the king. Tosses are underhand and most people do not throw hard. I'm not worried about dents and other impact marks so much, but it does need to be a material that wont chip away and create sharp edges.

I'm thinking that i'll use a threaded rod to mold the center channel that will accept the glow stick so that the end hole can be closed up with a corresponding threaded insert. That means the material also has to be durable enough to maintain thread interactions.

With all that in mind, what resin do you think best suits my needs? Something cost effective would be great, but i will certainly spend a little extra to do it right. I could also use a recommendation on a mold creation material. I figure i will create molds using the wood pieces pictured above so long as it wont harm them.

Thank you for your time & advice!
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Re: First casting project, looking for materials advice

Postby mangozac » Tue Sep 15, 2015 2:55 pm

Hi Jack, welcome to RA!

I must start by saying that your woodworking looks absolutely beautiful! You've certainly got some fabrication skills! With that in mind, I can't help but wonder if a better solution would be to machine some solid plastic blocks such as polycarbonate into the shapes that you want? I guess it comes down to how many you want to produce - are you doing this as a personal project or do you aim to produce many sets?

Reproducing parts like those in a clear resin is definitely not a simple task. You will need at the very least a vacuum degassing system and clear resin products often require a post-curing step in an oven around 70°C. Softer resins could be selected so that they are resistant to chipping. I'm not sure how well a screw in piece like you described will work: large pieces like these will likely exhibit a significantly different shrinkage rate to a small, threaded cap piece, preventing them from being able to mate.

Just some food for thought ;)
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Re: First casting project, looking for materials advice

Postby Jack.Straw » Thu Sep 17, 2015 1:41 am

mangozac, thanks! After i posted this i continued researching, and as much fun as i think this might be, i think it will be way too expensive. I calculated the volume for the pieces and it would take over 3 gallons of resin, plus molding materials, to make this happen. From what i'm seeing that means several hundred dollars and then I don't even have the right tools to do it right. I think your idea to just machine plastic blocks is probably what i should do, and my chances of screwing it up are marginally lower. I did some searching yesterday, before i read your reply, and was unable to find anything in the way of large plastic blocks. Pen blanks and flat sheets is all i could come up with. However, now that i've seen your post i will use the keyword polycarbonate and see if that helps.

Right now this is a personal project. I admit that i had grander ideas at first. If i already had the molds made, churning out sets for my friends and perhaps even to sell would be easy. Now that i see what it would cost to produce 1 set, both those things are out the window.

Thanks for taking the time to reply, and for your advice
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Re: First casting project, looking for materials advice

Postby mangozac » Thu Sep 17, 2015 8:19 am

You're right: the cost of both silicone and resin would be quite high, not to mention the chambers and other equipment required. Casting with clear resins isn't the easiest either.

Sorry I can't provide any suggestions for where to buy the plastic. Have you approached industrial plastics suppliers? This is the kind of requirement that they generally won't list what's available but if you speak to them they will be able to consult more obscure sections of their suppliers catalogue. They might even be able to suggest a more appropriate plastic material than polycarbonate. Acrylic/perspex is no good as it's far too brittle and will chip.

Good luck!
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