D&D Miniatures11/30/2006


Plastic Makes Perfect
Introduction to Design 08



It might sound odd, but the type of plastic we use in our miniatures and the means we use to form that plastic can affect their design. The best example of this is the gelatinous cube. You don't have a gelatinous cube? Well, there's a good reason for that.

Designers have dreamed about a gelatinous cube miniature since Wizards of the Coast started producing plastic miniatures. It's been on designers' set list three times without ever appearing in an actual set. We're not intentionally withholding it. Instead, the realities of plastic have prevented us from producing it.

It's not so bad, once you get used to the burning.It doesn't seem like it should be that hard. It seems like a simple task to float a skeleton and some weapons in a clear plastic cube -- like the gag toy of a fly in an ice cube. To explain why it's not that easy, I enlisted the help of one of our resident plastics experts, Bob Carrasca. Bob has a degree in Plastics Engineering, so he knows what he's talking about.

Bob related that the plastics can be broken down into two broad types that have different manufacturing processes -- thermosets and thermoplastics. Thermosets are made like waffles. The plastic is cast or compressed into a mold with a male and/or female half and then subjected to heat. This process changes the material, curing it into its shape and preventing it from being reprocessed for a different use. Most dice are thermosets. Thermoplastics are more like an ice cube. The liquid plastic is blown, extruded, or injected into a mold and allowed to cool to create a piece of solid plastic. D&D miniatures are made using a thermoplastic process.

The plastics used in a thermoplastic process are divided into three basic types -- amorphous, crystalline, and semi-crystalline.

Amorphous plastics have a mixed-up molecular structure that gives them decent resistance to environmental factors such as light and changes in temperature. They are strong, flexible, and tough, but their mixed-up structure means they lack clarity and they can change size unpredictably in the process of cooling.

In crystalline plastic, the structure of the molecules locks into place, allowing light to pass through. Crystalline plastics have great stability of size and shape, and they resist environmental factors well. Unfortunately, crystalline plastic tends to be rigid, hard, and brittle. It's more likely to break than bend.

Semi-crystalline plastic has properties of the two types described above. It retains its shape and size while remaining flexible, and it has good resistance to environmental factors. Unfortunately, it's generally more costly to produce, and it has poor clarity.

D&D miniatures are made of our own secret plastic recipe that offers tremendous resistance to breakage and ability to retain its shape.

Now that you have a basic understanding of some of the elements of plastics, let's look at some ideas for how to make a gelatinous cube, and Bob can explain the challenges involved in each strategy.

Matt: I imagine it might be possible to stick a painted skeleton and some weapons in a cube of clear liquid plastic and stick a base on it, much like you might put a toothpick in an ice cube tray. Bob, what would happen? Would it work?

Bob: The best process for your desired result would be a casting process. You could use clear crystalline grades of polyurethane or acrylic. This would allow you to cast harder or softer materials with small components randomly placed inside. However, this process takes much more time to output a part, and it's more expensive than our normal injection molding process. Also the material costs more.

Translucence is Hot!Matt: That sounds impractical. OK, so how about if we sandwiched a skeleton between two hunks of clear plastic molded to perfectly fit the skeleton. How would that work?

Bob: Of course, this is an option as well. Basically we'd create two halves of a cube and glue the skeleton between the two halves. Due to the propensity of thick plastic to sink, we'd have to hollow out the inside so that it would be like putting in a glass box or within a bubble of air inside the cube. The cost of assembly would be high because of the complexity, and the end user would see a seam line between the two halves of the cube due to the refraction of light.

Matt: That's not really the effect I'd like. What about if we just did a solid block of clear plastic. Would that work?

Bob: You can do this, but as I mentioned, the plastic would sink due to its thickness. Using our plastic, a thick chunk like you'd want would form a dip in its center as the plastic cooled. You could use a different plastic and a casting process, but the cost would be higher than for any normal miniature.

Matt: OK. So would an empty cube work? Like a box with no plastic inside?

Bob: There is no easy way of accomplishing this. You might be able to do it using living hinge technology -- you'd create a flat pattern much like how packaging is designed, fold it up into a box shape, and then have the seams sonic-welded together. But you'd still have seams. This process would be limited to certain materials like polypropylene, and the clear grades are not perfectly clear.

Matt: Ugh. Are there any other options?

Bob: Sure. You could make a box shape with one side open, like a squared-off drinking cup. The whole thing could be made of a single piece of plastic. We'd have to use a different type of plastic than our normal stuff to get it to retain its shape and to have enough clarity. We'd also have to run the piece through a separate production process. Still, it's possible that with enough quantity we could bring the cost down to a reasonable level to put it in a set.

Matt: Really? That might be pretty cool. If it didn't have a base then you could . . . Hmm . . .

Tell Me What You Think

Would you like a gelatinous cube miniature even if it has nothing inside? Email me your comments.

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