Mold Making, what methods do you use?


Trucklover

Trucklover

BNSF SD70MAC's
What methods do you all use when you are making molds? What is the best material to use? Is it better to make a rubber mold using the original part and then pour resin?

Im looking to cast some things for a cement batch plant/rock quarry im starting, Im using the Walthers Glacier Gravel Deluxe Kit as the base kit and need to copy several more of the resin parts that are included with the deluxe kit. These things are already damn near impossible to find, and expensive when you do, so I want to make a mold for the parts that I need multiples of and cast some. Just wondering what you all use when making molds of your own?
 
I have molded most of my coal loads. I used the kits from Hobby Lobby to make the molds, I think its a Alumlite brand. They have a quick-set mold or high strength mold. Both work fine, the high strength is more flexible, but costs more. Then I mix the two bottles (small amounts, only make what you can mold in a couple minutes as it starts reacting immediatly) of casting resin to create my peices. its really simple and works great.
 
Our club has had several really nice clinics from some of our senior members. They taught us to use the Smooth On products. Their secret was to make the molds extra thick but very pliable, using an RTV type product. We would build a mold box (water tight and square), put the object in the bottom of the box the pour the material in the box making sure the mold was 1/2" or larger than the object. This allowed the molds to be reused. I have some that I've used a couple of dozen times and the results (plaster) were excellent. here is a link to the website with more info that you want on the subject. :) http://www.smooth-on.com/
 
When I've made molds in the past off a natural formation such as shale, coal etc. I've first sprayed the area to be molded with mold release. Then I start painting on multiple layers of RTV. I wait until the RTV is almost dry before starting another layer. At 7 layers, I reinforce the mold with a layer of gauze, painted onto the RTV. I will add gauze for the next 2 layers. The mold is finished off with a thick layer of RTV, or multiple layers until the gauze can't be seen. If I need a real flexible mold, I'll only put in 1 layer of reinforcement, (gauze).

When the mold is completely dry, I peel it off, wash it with mild soap and water, and let it dry. Now its ready for use.
 
I use liquid latex sold in craft stores for making rock molds.

For casting cars, buildings and parts I use 2 part RTV. I have used the Alumilite and Hobby Silicones types of RTV. If you search YouTube for RTV molds or resin casting you can find lots of videos on how to do it.
 
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