I am currently experimenting with making plastic parts via rubber molds for HO scale buildings and structures. The results have been encouraging so far. I am interested in the experiences of others who have used molding of parts to build structures of their own.
Does anyone know a website or anyone here that would like to trade their molded parts for structures for mine? I have molded a couple of buildings and would be happy to trade for other molded parts and structures.
I have been very successful making castings from my own molds. I notice you said “rubber” molds. Forget that. Rubber takes forever to cure and many, many coats, and is too flexible to provide straight parts.
I use RTV mold material and hydrocal or casting resin form Micro Mark.
First make a mold box. It should be at least 1/2 inch from the edge of the pattern and 1/2 inch over it. The best method that I have found is to use the FOR RENT signs from HD. I rip them up on on my table saw to whatever height I need to fully cover the pattern plus 1/2 inch. I then measure the length and width and saw two sides and two ends at the same time so they are exactly the same dimensions.
I use 1/4 inch plexiglass, also from HD, as a flat base which is absolutely essential. I then stick the pattern to the base using rubber cement. I also use rubber cement to glue the bottom edges of the mold box walls. I then scotch tape the corners. I finish that by pressing modeling clay all around between the side walls and the base to prevent any leakage.
If the pattern is wood I seal it with a spray can of shellac to prevent the RTV from adhering to it. If necessary I use a mold release.
I have made a vacuum box of 3/4 inch plywood large enough to hold my biggest patterns. I use a piston type air pump to generate enough vacuum to de air the mold immediately after it is poured. This is absolutely essential to prevent little beads from forming on the finished casting.
I installed some threaded pipe fittings into the end of the box to which I attach the suction hose and the other end goes onto the air pump air intake with the filter removed. Cheap and effective.
When pouring the plaster or resin into the finished mold it is important to put it under pressure. I just reverse the air hose to the output of the air pump and pu