Molding/Casting

[ErMaC]

This thread will show you how to mold and cast your items in a step by step tutorial.

 

[ErMaC]

The first thing we did was make sure the item was sealed to ensure a good form. "Optional" we installed a flange on the bottom for the future, it will be explained why in a future post. Next we prepared 5 ounce plastic cups and filled them about and inch. we used those as keys for the mold, you will see those in pictures on the side. we let the keys sit in the cups for an hour. The amount of keys you need depends on the size of the object.
before we started to mold we cleaned and sprayed the helmet with 200 ease release. All product we used are smooth on products.

Equipmemt-

You will need gloves, mixing cups, mixing sticks and chip brushes. We used paint mixing sticks because of the thickness and size. We were able to get them free at Home Depot.

Products-

We bought 2 5gal buckets of Free Form Air Epoxy Putty, 2 gal of Rebound 25 silicone rubber, 2 gal of 65d "casting material", a small tube of THI VEX, it is a silicone thickener for the rebound 25 and is used on the 3rd and 4th coat, and a can of 200 ease release.

 

[ErMaC]

The first coat of the rebound 25 is a thin coat we used 150ml for each part A and part B 1:1 mix ratio. We had to make multiple batches until the first coat was complete. Spread the rebound around the helmet until every seam and crevice and surface was filled in. Use a chip Brush for the first coat.

 

[ErMaC]

I am going to note that you must do the rebound 25 in 8 hours. If you let a coat fully cure before the next coat, the next coat will non form to the previous coat. It will just lift off. We let the first coat cure for 1 hour. To test if its ready for the next layer dap it with your finger. If your finger doesn't pull any of the silicone off and is a tad pit tacky its ready for the next coat. Cut off the dangling drips carefully before applying the second coat. The second coat was complete with the same mixture amount as the first coat. 150ml each A and B. Spread it around with a chip brush and mix batches until the layer is complete.

 

[ErMaC]

Before we tested the second coat to see if its ok to start layering on the 3rd coat, we removed the plastic cups form the silicone we poured inside them to form the keys, Sorry I don't have more pictures of them. Next we started the rebound 25 again but we used a lot more at once this time. Because the 3rd coat is supposed to be a very thick coat. Add drips of tri-vex to the batch after the A and B mixture. Add about 5 drips at a time until the mix no longer runs form the mixing stick. Use the mixing stick this time to layer on the rebound 25. Make batches until the layering is complete and remember to add the thickener to each batch for the 3rd layer. Right after the layer is complete, install the keys around the item evenly on both sides of the. You might need to spread a tiny bit of the rebound on the surface of the key before you stick it to the sides. NOTE- Install the keys immediately after you completely layer on the 3rd coat, and layer the item with a thick layer.

 

[Shiroppi]

quick question . how much of rebound25 you endup using ?

 

[ErMaC]

quick question . how much of rebound25 you endup using ?

$190 for A and B mix
2 gal

 

[ErMaC]

The final coat of the rebound 25 gets mixed with thi-vex, which is a thickener so the rubber wont drip. For the final touch you add a thick flange straight down the middle for reinforcement. This is the end of applying rebound 25 and should be allowed to cure for a couple of days. REMEMBER TO THIS POINT SHOULD BE DONE IN 1 DAY.

 

[ErMaC]

Next is to take a razor and make a slit down the middle of the center bead. from end to end. You will be sliding something in the slit you just cut. The best thing to use is playing cards because of the coating they have. This is to separate the 2 halves of the mother mold. After the cards are in place spread wax or mold release all over the rebound 25 before the mother mold gets put on. This makes it easier to release the mother mold form the rebound. The last step is to install the mother mold. I used Free Form Air Epoxy Putty. It tested to be a perfect type of material to use for this job. It very strong and lightweight. Which is good because its a slosh cast.

 

[ErMaC]

After the Mother mold has cured for a few days drill holes and place bolts with wing nuts around the edge. Make sure you do that before you remove the mother mold. Remove the bolts then carefully pry the mother mold off with a flat head screw driver. Removing the mother mold the first time is the hardest time to remove it. It gets easier the more it gets removed form the mold. " be careful the first pull."

After the Mother mold is removed its time to cut out the original helmet form the mold. Make the proper cuts in the mold to safely remove. I cut a 5 inch line in the back and a 3 inch line in the front. To prevent detail inside the mold form tearing.

 

[ErMaC]

After the original helmet has been removed spray the exterior with mold release 200 ad make sure the interior is clean from and objects and also spray with mold release 200. Place the mold back into the mother mold and make sure the keys are back firmly in their positions, Then place the bolts and wing nuts in their holes.

I tried both 320 and 64d casting material. I didn't see a big difference so I used 320 for this mold. Its a 1:1 mix. The amount used is at your discretion. This size of the mold varies. This will have to be learned as you go along. To remove the casted helmet its the same process as removing the original. Just repeat the process.