Mold Making Question

Smooth On makes many different mold materials and casting resins. I have used their OoMoo 30 and Mold Star 30 with good results. The latter having a longer shelf life.
I have not used it for building sides but have friends who have. Learning curve is very short.

Most recently I cast this pilot.

Pete

Hey Norton, what did you use for the casting material itself?   Very good work by the way...now I'm getting interested in the possibilities.

Thanks, Dale

Dale, for that pilot I used “Alumilite Amazing Casting Resin”. I have also used Smooth On “Smooth Cast 300” with similar result. A local hobby shop carries Alumilite. You can order direct from Smooth On or Amazon or many other sources. Best if you get a number of projects lined up if you decide to jump in, some products only have a one year shelf life.

Here are a few other items I have made over the years.

Pete

I understood the original question to be that the poster has a building, and wanted to press something against the assembled building to make a mold for a part. If that is the case, it isn't as simple as pressing a loose detail part into a pile of mold-making material. The problem here is the mold material has to be flexible enough to form on and around the assembled structure detail part, but not so flexible as to distort when removing it from the assembled building and laying flat for using. Plus, he doesn't want it to leave a residue.

If it were me, I would try something like silly putty. In my experience (which may differ from yours based on various brands and compositions) it doesn't leave a residue. I think you could bend it over the part, remove it, and then "unbend" it to use as a mold. However, over time silly putty will flatten out so you need to use the mold relatively quickly. If it works, make a mold and quickly make a part in it, and then use that part to make a proper flat mold.

Yes, there might be some shrinkage and distortion from several generations of molds, but heck.... silly putty is relatively cheap. Worth trying.

Mold materials are not pressed around an object, rather poured on and allowed to cure. The master is easily removed from the mold when done providing you apply a thin film, scotch tape works, over any opening otherwise the master gets trapped in the mold. There will be no residue left on the original part.

Pete

@Norton posted:

Dale, for that pilot I used “Alumilite Amazing Casting Resin”. I have also used Smooth On “Smooth Cast 300” with similar result. A local hobby shop carries Alumilite. You can order direct from Smooth On or Amazon or many other sources. Best if you get a number of projects lined up if you decide to jump in, some products only have a one year shelf life.

Here are a few other items I have made over the years.

Pete

I am really amazed at the smoke deflectors, did you have a two piece mold for that?

Ray

@Rayin"S" posted:

I am really amazed at the smoke deflectors, did you have a two piece mold for that?

Ray

Ray, it was single mold for each side. I found the key to do that is make the mold just a little bit larger than the master so you can easily pry the castings out. Blue mold means it was done with Smooth On Oomoo 30. The deflectors have some give and not easily broken with careful handling.

The resin deflectors are on 3038. They have since been replaced as I wasn’t happy with the first set.

These Post War doors were done using the same technique. Single mold with thin sides.

Pete

Well, I'm impressed with your work and now I'll have to come up with some 'opportunities' to see what I can do with castings - apparently lots more than I expected.  Thanks for the tips!

Dale

@Randy Harrison posted:

Oh, great scenery gurus, I have a question about making molds to copy parts of models that have 3-D detail and shape.

A picture would be useful.....

Is there anything that I can press on a casting on a model building to form a mold to create copies in either plaster or resin that will not hurt by leaving a residue on the original being copied?

Pressed on; not the best solution.

Pressed into the RTV to make a mold; possible.  Again, a picture would help.

Residue? Not leaving that if it's good RTV - lots of types and sources.  More a question of the paint and/or finish being removed by the RTV process being possible.  Depends on the what you are copying and what's there.

I’m just throwing an idea into this discussion as food for thought…

Have you considered 3D printing to solve this problem? There are several large structure projects in the OGR 3D Catalog that show this could be done. It’s a bit more involved than making a mold, but once it is done, it’s done. Duplicate parts can be made without any danger of the mold changing shape slightly.

Making a mold is the “analog” way to approach this. 3D printing is the “digital” way to solve the problem. Might be worth some thought and exploration. Post the question on the 3D Forum and see what happens.

@Rich Melvin posted:

I’m just throwing an idea into this discussion as food for thought…

Have you considered 3D printing to solve this problem? There are several large structure projects in the OGR 3D Catalog that show this could be done. It’s a bit more involved than making a mold, but once it is done, it’s done. Duplicate parts can be made without any danger of the mold changing shape slightly.

Making a mold is the “analog” way to approach this. 3D printing is the “digital” way to solve the problem. Might be worth some thought and exploration. Post the question on the 3D Forum and see what happens.

@Rich Melvin

Rich:

Your suggestion is a good one. My son, Chris, has a 3-D printer but no CAD software to do the drawing nor time to do the drawing if he had the software. We have been using files from the OGR 3-D Library and from other similar file repositories. Is there any way of scanning the original piece and converting it to a file that is readable by a 3-D printer?

For sure 3D printing is an option and may be the only option for complex shapes like a track bumper but casting requires no computer or programming skills and no expensive equipment other than a sharp knife to make a container and a beaker of some type to mix the components. My observation is it also produces better resolution than a filament printer and at least as good as a resin printer.

I have a few molds I made 15 years ago that still produce as fine a casting now as when I made it.

Another example. When I detail an older steam locomotive I like to add cab curtains and a cab apron. I just made a mold using MTH cab curtains.

Pete

@mwb posted:

A picture would be useful.....

Pressed on; not the best solution.

Pressed into the RTV to make a mold; possible.  Again, a picture would help.

Residue? Not leaving that if it's good RTV - lots of types and sources.  More a question of the paint and/or finish being removed by the RTV process being possible.  Depends on the what you are copying and what's there.

@mwb

Thanks for the reply. What I wanted to copy was a section of a wall on a Department 56 building, but I now realize that this is an impractical idea. However, I also would like to duplicate small architectural details on models of buildings that would lend themselves to a press-on type of mold template. Is there a substance that would accomplish this?

N.B. that it is quite possible to use a 3-D printer to make a mold that can then be used for producing multiple parts. Sometimes this is the cost-effective solution.

Also, the 3-D scanning ability of phones that have lidar sensors is getting pretty impressive. Useful when matching or reproducing existing parts with a 3-D printer.

@Avanti posted:

Also, the 3-D scanning ability of phones that have lidar sensors is getting pretty impressive. Useful when matching or reproducing existing parts with a 3-D printer.

Scanning is what I was thinking @Avanti because measuring curved sections requires a bit more effort and massaging in my experience. I only have calipers to work with though.

@Randy Harrison posted:

@mwb

Thanks for the reply. What I wanted to copy was a section of a wall on a Department 56 building, but I now realize that this is an impractical idea. However, I also would like to duplicate small architectural details on models of buildings that would lend themselves to a press-on type of mold template. Is there a substance that would accomplish this?

If you read my response near the top I suggested a method to do this. It may or may not work, but it won't hurt anything to try it.

Randy, post your question about scanning an item for 3D on the 3D forum. I think someone there may have an answer.

I cannot personally answer this because I have no experience in 3d Printing.

@Randy Harrison posted:

@mwb

Thanks for the reply. What I wanted to copy was a section of a wall on a Department 56 building, but I now realize that this is an impractical idea. However, I also would like to duplicate small architectural details on models of buildings that would lend themselves to a press-on type of mold template. Is there a substance that would accomplish this?

Maybe not impractical, just something that takes planning and a bit of applied thought.

May just be like a build a "dam" of clay about the feature to capture it in RTV to pour resin kind of exercise.   Quite doable with care and probably most important is getting everything level.

Need clay suitable for purpose and most any type of RTV.  Resin is easy, but I prefer a 6 min working time resin vs. the usual 3 min stuff you get from Micro Mark, etc.  Check out:

Freeman Manufacturing & Supply Company

https://www.freemansupply.com/...ials/silicone-rubber

I had crown made (several actually) and the dentist makes a mold of your teeth with this rubbery goop that sets up in seconds, Then they make a new tooth from that mold. Not sure what the stuff is, but I can see uses for it here for small parts...yes/no??