October 17, 2012
From 3D Drawing to Small Scale Production.

When we began planning the prototype production of our Dice Domes for The Roll Call Project, we hoped we would find something on the market that fit our needs.

We checked Alibaba.com, Uline.Com and other suppliers for containers that would meet the requirements we had for our game. While Alibaba had many many things to offer, and we were offered many things that they didn’t actually have, it quickly became apparent that what we needed was not out there- even as a makeshift stand-in.

Once we made the decision to customize, we began looking for small run production companies. The lowest cost we could find was 800 Dollars for setup, and 75 Dollars a unit- this for silicone molding. How hard could it be to do it ourselves? So, we decided to get underway. 

1) Create a 3D Model. While there are great open source 3d Options available, we had access to Solidworks and used this option. The final design included a raised copy of our logo. The logo design was made in Inkscape (http://www.inkscape.org) and imported to Solidworks as a DWG file.

2) Get a 3D Print. Once the model was finalized, it was uploaded to Shapeways (www.Shapeways.com). On our first attempt, we were rejected due to a problem with our tolerances, we had lines thinner than .7mm. After correcting this problem we resubmitted the model and were in possession of our Dice Dome within ten days or so. 

General precautions from here on out: This isn’t photoshop, autocad, or minecraft. This is real life: fumes, stains, and all. Make sure to work in well ventalated areas, wear eye and skin protection, and make sure to take breaks. Don’t get scared off though, its no more precautions than you would need for scrubbing your tub! 

3) Make a Two-Piece Silicone Mold. While we loved our prototype, you can’t play Roll Call with one cup. You can play Roll, I suppose, but that is only half the fun. No, we needed to make more. Shapeways charged us roughly 48 Dollars for our dome, which is very reasonable for one model- but becomes expensive quickly when you need fifty. We decided to go for Silicone Molding.  A big, big help was the detailed series on youtube by XanderXereus (Part One begins here: https://www.youtube.com/watch?v=jFfXT_Cjpuk). This gave us a solid place to start. 

 I think its going to be time for a nice, ordered list to describe the process from here on out. It is a cycle pretty much repeated twice, once for each side of the mold. 

  1. Create, find, “acquire” a container that fits comfortably around your mold. The video above used Lego to form the outside shape of the mold, but sadly we didn’t have Lego on hand anymore (please, don’t take our geek cards). Instead, we used a shadow box hot-glued to a flat piece of plastic. Because the shadowbox is basically a box that is open on two ends, it made it easy to cut off the hot-glue and eject the cured piece of mold from this outer mold of the…mold. Keep this in mind when selecting your container!  We recommend a straight-sided container, as it will allow more stable orientations for the finished mold.
  2. Fill the base of the container with Plasticine or modeling clay. Try to make it smooth, as any texture or flaws will be reflected in your final mold.
  3. Apply sealant to any and all porous surfaces. This will include the model if it comes from Shapeways. Pay special attention to detailing, but do not flood the details with sealant.
  4. Place your model on the clay.
  5. Make “Keys” by placing small objects halfway into the clay, around the edges and away from the model. These will help you line up the two halves of the mold later. Do not make them symmetrical: either arrange them so that only one alignment of the mold sides could ever seal properly, or use a mix of shapes.
  6. Apply releasing agent to any and all surfaces coming into contact with the Silicone. Pay special attention to detailed portions of your model.
  7. Mix your silicone of choice according to the included instructions. We tried OOMOO 30 and OOMOO 25 and went with the 30. It created a firmer, more stable mold and was well worth the extra curing time. OOMOO25 cures in an hour and a half, while OOMOO30 takes six hours. Its two parts mix in a simple ratio of 1:1, making a nice smooth lavender color when properly blended. 
  8. Pour the mixed silicone as slowly as you can starting from the farthest edge, allowing the silicone to slowly fill over any detail you may have in your mold. Give yourself a half-inch to an inch of clearance between the top of your object and the fill line of your mold. 
  9. Allow to cure.
  10. Remove the mold from the container. Remove clay and objects used as “Keys”. DO NOT REMOVE MODEL. Clean the surface to remove any clay particles. 
  11. Replace mold half into container, with unmolded side facing you. 
  12. Apply release agent to all surfaces that will be touching Silicone. 
  13. Mix and Pour Silicone Rubber again. It will slowly flow, filling the cavities left by the removed keys, and covering the model. Once again, allow a half inch to an inch of clearance.
  14. Allow to cure. If your model has fine detail, we recommend letting the silicone cure for 24 hours before extraction.
  15. Remove mold from container, open and slowly remove the object. You now should have a negative of the object you are trying to make. 

4) Prepare the Mold for Casting. Study the location of the seam on your mold. Where will the resin flow once it is poured into the cavity? How will the air that the resin is displacing escape from your mold? Once this is understood, determine an appropriate location for your sprues. A sprue is a channel through which you will pour resin, or through which air will escape the mold during resin pouring. Much like pouring the silicone, you will want to make sure the liquid resin can flow OVER the detailed portions of the cavity. Consider the different orientations your mold will allow you to use. Often, the side that was “up” when you poured your mold will not be ideal for pouring into the cavity within. Remember that the resin will always flow down, while air can only escape upwards. Find a point at the top of the object you are casting that will naturally collect air bubbles, and locate the end of your air escape sprue there.  When you have determined the where resin should fill the cavity, and where air should exit- use a hobby knife to cut small channels from the seam to the outside of the mold. 

5) Make a Resin Cast. Make sure to have plenty of small cups and craft sticks handy for mixing and pouring. Use rubber bands, or other mechanism for putting reasonable pressure on the mold for the purpose of holding in the resin. Be careful though, as the silicone is flexible, and you might warp the cavity inside. Try to apply pressure across a broad surface area.  Mix your resin according to the included instructions. We used SmoothCast 300 from OOMOO. Like the silicone, it mixes in a simple 1:1 ratio by volume with part A and B. Please read the data sheet that comes with these materials! There is lots of good information int hem.  After mixing completely with a disposable craft, slowly pour into the mold. When it has completed curing, remove from mold. Don’t futz with it for a while; even though it is firm enough to demold, it won’t be usable for a few hours. In our case, we needed the cup and lid to fit together nicely, so we fit our demolded cup into the lid at this point, so they could cure into a compatible shape.

6) Get Creative! Notes on Colors, Blending, and Additives to come!

There you have it. With one 3D print get enough prototypes to fit your needs.

In our case, a Launch Party!

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