Resin Casting Guidance

Hi Hobo Tim,
Are you using super glue(cyanoacrylate) to stick the styrene walls to the base to make the frame for the mold?
Thanks in advance for your reply.
-Rainer

Rainer,
I'm not Tim, but I use CA, (super glue) to glue my styrene mold box pieces together.
I use a slightly thicker piece for the base, but you do not need real thick pieces for the walls.

You can build a mold box in a couple of minutes. I use a paper cutter to cut my styrene pieces. That way, the sides are always straight. I use medium CA to do the gluing job.
Loren

Thanks Loren:)

I use Ambroid's Solvent for plastics. I prefer it for it dries quick and seals the styrene sides to the styrene base. The sides are .040" and the base is usually .080". The base will warp if you use .040".

If the base plate gets build-up from being glued alot, I use a hobby knife blade to scrape the raised gunk off and gives me a smooth base again.

Loren has a great idea of using the paper cutter to make straight square edges as this is needed.

What I try to do once the first half of the RTV mold is cured is to remove the sides carefully from the base in one piece with the RTV mold. I leave the sides glued to themselves except for one corner.(picture a box with no top or bottom, just 4 sides. Then cut one of the corners leaving 4 sides secured by three corners) Carefully separate one corner and peel the sides from the RTV mold. When you are ready to pour the second half of your mold, all you have to do it re-position the sides around the RTV mold and re-glue that one corner and the shape of the sides remains the same as the first half of the mold. Just a trick I learned. Doesn't always apply, but does for most molds I make!

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Complex Molds!!! I have made several molds in the past that consisted of three pieces. Two halfs and a squish center. The Grain Elevator Storage building (the red elevator side building) and the Top casting on top of that building were 3 piece molds. These molds take lots more time making them. They were a challenge, but well worth it. I think I made a 4 piece mold once, but can't recall what it was for. Anyways, a challenge like that is good.

Hobo Tim

And Tim, that is some snazzy means to keep your mold box in tact for future use.
I admit that I use too much glue in cementing my sides together, but I've never tried anything fancy as you describe so I don't care if I tear the mold box apart when removing the mold from the box. Plus, I have yet to use that cement you mentioned.

I will gladly bow to your expertise in the mold making business..

I am grass hopper, you are master:) darn rice paper anyway:blink:

In the past I've used lego bricks to make mould boxes. It works quite well.

soccrdad30 wrote:

Wow... This has turned into a very interesting thread. Tim, I love your project details. And I have seen alot of different videos on how to make a mold base whether out of Legos or hot glueing styrene/glass strips. I want to start out the simple way of course with simple impressions, and then to the squish casting.

Am I assuming the pressure pot is more for mass production? or higher quality?

And for the resin to have a longer setting time, is that better so one can work with it longer? Meaning getting bubbles out better, and having more time to modify casting?

Thank you again.

John K.

Some very good questions John.

I use the pressure pot for higher quality. Depending on how complex the detail is in what ever you want to cast multiples of depends greatly on how you design your molds. Most of my complex detail molds have to be filled very, very slowly to allow the resin to creep into all the nooks-n-crannies on its own. To force a pour quickly will develope huge air bubbles that a pressure pot with 1000psi won't make disappear. Pressure pot is for those castings you want to come out perfect every time, or at least give them a higher percentage of success than not. Higher Quality.

Also with this is the fact of using vent holes in the places where they most likely will congregate. Remember, most air bubbles move up, unless some mold detail prevents them from moving. Mold design is key to first of all eliminate bubbles. When I first started making molds and casting I probably had a 45% successful rate at casting, some items maybe 25%. With a limited budget that hurts when most of a set of resin was wasted. With the use of a pressure pot and with a better knowledge of making molds now I have about an 85% success rate or better but there are still those few items I try to cast that give me heart ache every time.

Designing a Master; When I scratchbuild anything that I indent on casting multiples of, I will design it for easy casting and assembly. Some items I have been working on recently are just that, complex yet easy. It's all in the design. Don't scratchbuild a sophisticated item in one piece, make it in easy to cast pieces. Might eventually make 4 pieces that will easily glue together into that one piece. Simplicity is a key for scratchbuilding masters for casting.

Man if I ever knew what I would be getting into when I jumped in the world of mold making and casting I doubt I would have made that leap, but here I am!!!

Wow, that was a long answer to the first question, but everything seemed to fit.

Working time; If you have a simple mold that has limited detail, then a quick set resin may work for it, but most of the molds I make I need the resin to remain watery till the molds are filled and I can work out any bubbles that might be a norm. Once the resin starts to gel all you can do, if you are not finished it to set it to the side and once it is hardened, toss it in the trash. Work time is key when filling the molds. Remember, room temperature is a key when mixing resins. The warmer the room the faster it will set, even faster than the listed time. 3 minute resin might start to gel in 1.5 minutes. Can you effectively mix, pour and top off the mold before time runs out. Give yourself some extra. I know, 3/10 minute resin compared to 10/30+ resin is a big difference. I use the later and still set my timer at 54 minutes because 30 minutes is not enough. Mix, pour and finish mold in less than 3 minutes and break part out in 10 minutes. Not with the detail that my masters have. Maybe one casting at a time, but not 4 or more. When I mix resin I am filling many molds, even if it is 1.5 ounces. Remember, we are working with Z scale, 220 times smaller than life itself.

I view a longer work time as being better for me, your castings may be simple and you prefer to use the quicker setting resins. Call it personal preference! Heck, most of what I have described in these messages is my personal preference of how I cast and make molds. Experience is personal.

Master Craftsman Joe D'Amato of Micro-Trains had the priviledge of working at a Disney design studio. Some of the photos of things he has made and the things he has written about creating have amazed me. I know from reading his messages on such topics that he has his own personal way of molding and casting that are similar and yet different than mine.

Mold making and casting is a road least travelled but very accessable. Take that fork in the road up ahead and give it a try yourself. You can always put it in reverse and get back on the road you were travelling on. My personal experience is nothing more than a map for you to follow and hopefully not get lost!!! Unfortunately I can't forsee all the bumps in the road, those you will learn from as I am constantly doing.

Have fun!!!

Hobo Tim

i ve been molding for 21 years now,, and the best i find is alumilite products!!!! but it all depends on exactly what your molding. go to their site,, they ve got all the info needed on what you need for everything from plastic to metal casting. i ve molded more cars than you ve ever seen using their products. i go through their gallon jugs monthly, and even have full account status there,, thats how long i ve used there products. it s super easy to do, and actually alot of fun. i ve bought one kit of something, and made hundreds ,ofcourse just for me!! i even designed my own vacuum machine for bubble removal(((www.joewoodworker.com) contact me anytime if you need any help. liltoot