Large Scale Central

Making molds and castings

Modeling
#1

Ok I’m starting a new post for this subject cuz last time I didn’t mean to, but kinda opened a unexpected can of worms…Anyways… I picked up a box of Alumilite High Strength 3 mold making kit at Hobby Lobby today. I went with this to give this part of the Hobby a go at. I also got 40% off the price too!. So You guys that have experience with anything like this stuff?. I need all the help I can get.

Dave Taylor…I am ready to take you up on your offer to help me along to learn, and anyone else that has experience in any type of castings and molds. I want to learn to make my own stuff to save a little bit of money, but foremost to say that “I built that” So ready or not mold making I’m here…LOL

#2

I have approximately 100 RTV molds both made by me and acquired (club ownership) from Peter Todd a professional train landscape artist. I buy mold with both polyurethane and polyester. I purchase most of my RTV and monomers from ww.rawmaterialsupply.com. The price is about 25% of the Aluminalite with is polyurethane. These materials are very to work with. The suppliers are very friendly to talk with and will guide you through proper selection and/or problems. I would be willing to privately(email [email protected]) answer any questions or assist.

#3

OK Travis… et all… it’s really easy to start and get good results. Where are you for knowledge on what to do? What have you read, and a little basic of where you want to go, and what you would like to cast would help.

Here is a link that covers the basics pretty good,

http://www.b9robotresource.com/molding1.htm

One of the first considerations is what you want in the finished product, and what and how it will be used for. Knowing where you want to end up, sets up what you will need to get there.

There are a variety of RTV rubbers, each with its own properties to be used for certain needs, some more stretchy and some much less so. some will hold up for a long time usage and others much shorter life cycle.

Let me know where we need to start and where we need to go…

And remember rule #1; Thou Shall Not Copy Someones Work Without Permission.

#4

Im looking at making some detail parts for railcars…building windows, doors small stuff like that. What does it take to make a master and how?. I have used and mixed resin before. I do not have a vaccum pump as shown in the article, is one neccesary?. I also have no plans to copy anything as you talked about in earlier post… Is the kit I bought worth messing around with?, made by Alumilite. …Travis

#5

The vacuum pump isn’t required, it does make things easier, but if your careful you’ll make perfect molds with out it.

What you’r wanting to make is the perfect things to get started on.

Rule #2: ANY CASTING WILL ONLY BE AS GOOD AS THE ORIGINAL YOU START WITH!!!

Keeping that in mind, we tend to use the 3’ or 5’ or 10’ rule a lot in the garden. I wouldn’t spend a ton of time on a master for something that won’t be seen up close. OTOH detail parts on a show piece, needs to be perfect.

You can make the master out out of any thing that’s not porous. At this experience point I wouldn’t suggest trying anything to complex yet, keep it simple without any undercuts or complex shapes. Finnish is important on the master (Rule #2). If in doubt you should seal the master with a light coat of clear acrylic spray. The RTV won,t stick to most things, except itself, glass, and a few other things, unless they are porous like wood, and it doesn’t stick to the wood, it kinda soaks into the openness of the surface. The RTV (Room Temperature Vulcanizing) will pick up an incredible amount of detail from the master. So if you want a wood grain on the final piece, make the master out of wood, but seal it before molding.

I haven’t used that particular kit, but they are mostly all alike and will do just fine for starters. You must follow the mixing directions for that kit… When the time comes to pour the mold.

Time to make the master!

#6

ONe thing about Alumilite, it cures like a door slamming shut,Im you find you need addidtional working time chilling it in the refrigerator slows the cure time…

Like Dave says, start small, with a one piece open face mold…that majority of stuff I do for RR purposes are simple one piece flat molds…I use the CR300 resin and RTV from Micromark, its good stuff easy to use, and comes in quantities that won’t go bad before you use it all up…

#7

I’d say that an air compressor and a paint pot work just as well as a vacuum pump to make bubble free molds. Yes it does tie up the compressor the whole entire time the RTV is curing, but I can live with that.

If you already own an air compressor, go out to your nearest big box hardware store and buy yourself a paint pot. You can then cap off one outlet, and then on the other add a ball valve and a pressure gauge. Voila instance pressure vessel that will hold fairly good sized molds.

Garden Railways had a series on casting and mold making by Burl Rice. He’s over on MLS, so I’d talk to him about casting questions. Edit: GR articles are June 2007-Feburaury 2008.

I use Alumilite, and RTV from Tap Plastics (not sure the exact name brand).

I felt the Micro-Mark stuff was good for a brief introduction, but the alumilite works much bet in my views.

Craig

#8

Travis, the weekend is ahead, where we stand on the casting? Any ?s.

#9

Dave,

I bought the resin kit today at Hobby Lobby. 40% off sale again… :slight_smile: Alumilite kit also. So I will be ready to go soon. We are out of town so no railroad work this weekend til Sunday nite when we get home…Travis

#10

Dave,

I bought the resin kit today at Hobby Lobby. 40% off sale again… :slight_smile: Alumilite kit also. So I will be ready to go soon. We are out of town so no railroad work this weekend til Sunday nite when we get home…Travis