Mold Making

Prime

I want to start making my own molds for resin to knock out items for D&D and other table/boardgames. I've researched bits that I need and it seems fine. So im after any advise/experience. I want to start small and work up. So starting with simple geometric shapes like wooden crates etc. I've roped an artist mate into joining me and making the master object to build the mold with so dont have a problem there.

Advise on best and hard wearing resin to use for the casting itself also welcome.

msuitepyon

Hands-down the best supplier of casting materials I've ever encountered.

http://www.smooth-on.com/

ceres

@tapeslinger

Asher

For making the kind of molds you want, Lego is your friend. I usually build a box of lego around what I want to cast to make the mold itself. This makes it super easy to do 1 part moulds and pretty easy to do 2 parters as well. Do you want detail on all sides of the box, or are you ok with flat bottoms? One part molds are how I got started as they are really easy.

In terms of materials I use a silicone rubber for the mold called Pikysil, but I don't know whether that's a uniquely Australian thing. Forthe casting I use a generic 15 minute setting resin.

Prime

Im fine with flat bottoms for now. Lego is a genius idea. I was thinking about how best to build a box.

Got any tips on how you started?

Echo

@Ein knows stuff.

Crazy stuff.

tapeslinger

Hi there, Prime!
(thanks for the @, @ceres!)

What sort of shapes / items are you looking to make, in terms of board game parts? Having a good idea of how simple or complex the item is will be helpful for explaining how to mold and cast it.

Full disclosure: my day job is literally "technician" for a company which sells Smooth-On and other brands of molding and casting products.

Prime

Anything you can recommend would be great. Starting Off with crates, chests and barrels, like to move on to tables, chairs and eventually statues and alters more detailed bits, In 28mm scale.

Dr_Keenbean

I'm actually looking into doing this myself. I want to start making my own custom parts for 28mm miniatures.

My initial searching turned up a series of youtube tutorials specifically to cast 28mm resin miniatures on the cheap. How fortuitous.

youtube.com/watch?v=jFfXT_Cjpuk

Asher

I'm fortunate enough to know a guy who does a lot of resin casting so I was able to bother him for advice. Aside from that, youtube tutorials like the one Dr_Keenbean posted are where I got most of my info.

My gut feeling is that one part moulds will be enough for simple crates, but for barrels which are fatter in the middle, statues etc you will need a 2 part mould. Part 2 of the posted tutorial is pretty much how I go about making 2 parters.

tapeslinger

Vids like @DR_Keenbean linked there are pretty much how it's done, yeah. The only problem with the Pour-On Mold-Making starter kit Smooth-on sells is that it's like, their least awesome rubber, and they make a lot of really great stuff. In terms of price and value, Smooth-On is pretty much on top of the game. (It's just the rubber which is the least likely to be able to be fucked up, tbh: you practically have to try to fail with Oomoo 30. The learning curve with some of their other stuff is steeper, but Oomoo 30 is not exceptionally durable, and for a silicone it's on the firm side, which means demolding delicate things can be super frustrating.) That kit also comes with a DVD from Smooth-On, which can be useful. The price of the kit is less than the retail price of each of the components if you picked each one up separately, so as far as "a place to start" goes, it's not a bad deal. You might find yourself wanting to switch-up to a better silicone pretty quickly, as you get better at mold-making, but it depends on the volume of parts you want to make, too. If you need like, 5, and then you're done, that kit's going to be just fine.

Depending on the flexibility of the rubber you choose, if you end up buying separate rubber and casting resin, most of the items you want to make for your initial run would probably work as one-piece molds, but it depends on the number of casts you want and how perfect you want them as well. Do you have your original models ready to be molded, or are you sculpting them yourself?

Barrels might need to be a 2-piece mold if you use a stiff silicone like the Oomoo 30; chairs and statues will depend entirely on the design of the chair, statue, etc, but will probably be 2 (or more) piece molds. For 28mm, it's often simpler to mold those tiny things by breaking them down into their component parts; that's why parts from Reaper, Citadel, et al, or from resin statue kits, are broken down the way they are (with the added benefit that they're easier to ship and the end user has a lot more ability to customize the figures they make!)

Lego and foamcore are my go-to mold box materials; super simple. I usually use hot-melt glue for securing one-piece molds; for two-piece molds I use a clay we sell at my shop called PermoPlast. (In a time long ago this clay brand was called "Klean Klay," it's one of the standard terms you might see in a mold tutorial. In any case, "clean" here refers to a lack of sulfur and other rubber-murdering chemicals.) It's so freaking important to make sure that whatever clay you use for your mold parts is sulfur-free because otherwise you're gonna have a bad time. Sulfur basically prevents the silicone from curing; solvents like denatured alcohol, d-limonene, and acetone, if they're lingering on the surface of your models, can also cause cure inhibition. Additionally, some components of things like soap, such as stearates and perfumes, can cause this as well. The Oomoo 30 is a tin-cured (condensation-cure) silicone, so it's a little more stable in contact with undesirable chemicals, but it's best to bypass that problem entirely if you can.

One thing I noticed is that the explanation in the linked video regarding what RTV means is sort of confusing. (Vulcanization is the process by which a material becomes a rubber; old standards like latex require aging processes with heat in order to be "vulcanized." RTV -- room temperature vulcanization -- means the material rubberizes at room temperature, meaning it doesn't need boiling or other methods to rubberize it.)

Release agent is another key thing for multiple part molds. it's not mission critical for one-piece molds in silicone but it can make things go a lot smoother.

I think that's enough information to get you started! Let me know if you need more help. (If you would like my work email address, I can PM you with that information as well.)

Prime

Great, excellent info. I found the UK distributor for smooth on stuff. Looks like I can pick up a trial Oomoo 30 kit for around £30 so thats fine for messing around with. But there doesnt seem to be a middle ground. Its either trial kit or super large kit. Also not seeing mention of a DVD. So might be looking at the wrong kit? Or are you thinking of this one?

Went back to my parents over the weekend and raided the loft for lego so im fine there, despite the funny looks!

My friend is hand crafting the original objects, he's already made the first crate, although im not sure what out of, from the looks of it from the photo a type of soft modelling wood? But I dont know what materials I should tell him to use or avoid. Can any materials damage the silicon during the vulcanization process?

tapeslinger

oh, the one depicted in the video Keen linked is the Starter Kit, which has trial sizes of the rubber and the resin as well as some accessories. Oomoo 30 is only available in a 2-pint or a 2-gallon; there's no middle size. I'd start small though. The price on the Starter Kit looks much better than the per-unit price on the individual products, especially if you are in the UK.

As far as things to avoid for your models-- wood is ok, just make sure it gets sealed with a clear sealer like Krylon or any other clear acrylic sealer; amber shellac is a sulfurated product so avoid that.

Cure inhibition is pretty much the only thing you'll need to be wary of, really-- like I said, Oomoo is a good starter rubber because it's pretty difficult to mess up.