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Step 6The Board- Making a mold from the Lego master
Now that we had a master, we wanted to make a mold in order to replicate it. After some research we found Smooth On, specialized in mold making, and after even more research we found a reseller in Spain, From FX. I ordered a bucket of Mold Max 30, a very resistant, rubber compound.
In order to make a mold it is necessary to encase the master:
-first, I cut a polystyrene square to make the base of the board. since I was using thin depron-s sheets that I had form the first prototype, I cut two and glued them together to make the base thick.
-I put the base under the grid; then I cut a slightly bigger polystyrene square, put it below both the grid and base, and "attached" everything with duct tape. I also covered the sides with duct tape to cover all the exterior seams between blocks and give it a smooth look (see pictures below).
-I then "painted" all the grid and board with alkyl (two layers). This step is ESSENTIAL, otherwise the rubber will get in the seams between the Lego Blocks and also between the lego grid and the polystyrene base, thus ruining the mold (and the grid too, since the only way to remove the rubber is by undoing the grid). After this step the blocks will stay glued forever, alas!
-Finally, I cut some walls of the same polystyrene board I used for the base and made a frame to contain the rubber.
Now comes the most delicate part of the process: preparing and pouring the rubber in the frame.
-Mold Max comes in two parts that must be mixed 10 to 1 in weight for it to become active. The main part is white and the catalyzed red, so the mix results in a characteristic pink colour. It is extremely important to mix both components thoroughly, or the parts that didn't mix well may not cure properly.
-Before we poured the rubber, we sprayed the board with a release agent to ensure that we could remove the mold from the master with minimal effort later on.
-Pouring the rubber must be done in a proper manner so that no air gets entrapped. "A proper manner" actually involves degassing the mold, but in this case we poured the rubber slowly from the sides to the center and then prayed.
-In order to make the rubber mold for the board, we used some 4.5 kilos of rubber. Mold Max is expensive, but it is better to order more than it is needed than not ordering enough, believe me :P Same applies when pouring: prepare more rubber than you think you'll need, or you risk having to prepare more afterwards on the fly, which is not a good idea.
-The last pictures show the rubber in the frame, and the finished mold. If you take a close look a the pictures you'll see some small defects. Releasing the mold from the master took some time and some strenght, but the rubber showed up its properties and came off on one piece :)
-Now that we had the mold ready, we moved on to...
In order to make a mold it is necessary to encase the master:
-first, I cut a polystyrene square to make the base of the board. since I was using thin depron-s sheets that I had form the first prototype, I cut two and glued them together to make the base thick.
-I put the base under the grid; then I cut a slightly bigger polystyrene square, put it below both the grid and base, and "attached" everything with duct tape. I also covered the sides with duct tape to cover all the exterior seams between blocks and give it a smooth look (see pictures below).
-I then "painted" all the grid and board with alkyl (two layers). This step is ESSENTIAL, otherwise the rubber will get in the seams between the Lego Blocks and also between the lego grid and the polystyrene base, thus ruining the mold (and the grid too, since the only way to remove the rubber is by undoing the grid). After this step the blocks will stay glued forever, alas!
-Finally, I cut some walls of the same polystyrene board I used for the base and made a frame to contain the rubber.
Now comes the most delicate part of the process: preparing and pouring the rubber in the frame.
-Mold Max comes in two parts that must be mixed 10 to 1 in weight for it to become active. The main part is white and the catalyzed red, so the mix results in a characteristic pink colour. It is extremely important to mix both components thoroughly, or the parts that didn't mix well may not cure properly.
-Before we poured the rubber, we sprayed the board with a release agent to ensure that we could remove the mold from the master with minimal effort later on.
-Pouring the rubber must be done in a proper manner so that no air gets entrapped. "A proper manner" actually involves degassing the mold, but in this case we poured the rubber slowly from the sides to the center and then prayed.
-In order to make the rubber mold for the board, we used some 4.5 kilos of rubber. Mold Max is expensive, but it is better to order more than it is needed than not ordering enough, believe me :P Same applies when pouring: prepare more rubber than you think you'll need, or you risk having to prepare more afterwards on the fly, which is not a good idea.
-The last pictures show the rubber in the frame, and the finished mold. If you take a close look a the pictures you'll see some small defects. Releasing the mold from the master took some time and some strenght, but the rubber showed up its properties and came off on one piece :)
-Now that we had the mold ready, we moved on to...
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