People Keeping Mold-A-Rama Alive | Hacker News Reader

People Keeping Mold-A-Rama Alive

atlasobscura.com

70 pointsartsandsci17 comments

I grew up collecting these from the Milwaukee County Zoo. I never realized they were a somewhat regional thing. Neato!

Just seeing the picture of the machine brings back the melted plastic smell. I remember trying to collect each one at the Milwaukee zoo, and inevitably breaking the head off of them before long.

I've always found these machine fascinating, never seen one in person though. I am surprised the molds are aluminum instead of steel. Typically aluminum molds are considered suitable for smaller runs only. If they do 100 parts a day that's 36.5K cycles per year.

Why is aluminium considered suitable for smaller runs only out of interest?

Aluminum is softer than steel, so the mold wears out quicker—the models lose details.

and it's much cheaper to work. If you're only doing a couple thousand moldings, you don't care as much about mold life

Ah cheers that makes sense. One thing I was wondering would they use stainless steel for moulds, to prevent them rusting?

Nope, "real" molds are made out of tool steel. Corrosion isn't really a problem since machines are typically stored indoors.

The casting material is so soft, I suspect the molds are barely perturbed.

Might the thermal properties of aluminum make it a better choice for these quick turnaround castings? Quick to heat, quick to cool.

They have several machines at the Lowry Park Zoo, in Tampa, Florida. I got one a few years back—the hippopotamus that is shown in the article. I love it, and if I ever get back there, I'm going to get a few more. It was cool to do!

They're all over the San Antonio Zoo as well. My kids loved making them.

I am actually coveting one of those little plastic toys. I need to think on this for a while :)

I find myself coveting a Mold-a-rama machine to make molds for it :-). Injection molding is pretty expensive to do in small quantities, I would like to have a 'table top' machine where I could trade time for money.

Combine this:

https://makezine.com/projects/make-41-tinkering-toys/diy-inj...

With this:

http://www.instructables.com/id/Home-Plastic-Injection-Moldi...

Alternatively, you can purchase a hand injection molding machine as mentioned in the above instructable, if you don't want to build your own:

http://www.easyplasticmolding.com/model_150/home.html

...for $1800.00. So - if you have more money than time, materials and skill - well, it's possible.

And they are reasonably close in Scotts Valley. I'm definitely going to have to get one of those.

EDIT: Interesting that the Makezine article has a pretty big problem. It doesn't actually show you how to make the 'second half' of the epoxy mold. To make the second half, you would have to assemble the mold and then pour epoxy into the assembled mold. Depending on the material you'd probably end up some how pumping that epoxy in, and you would need to pull a vacuum on it to avoid bubbles.

Its a nit of course, but worth considering.

For desktop use, it seems like mold-making combined with a lab heater for ABS/whatever you're going to use would make it cheaper-still.

I used to do investment casting with silver, and that's mostly the way it worked. ABS is much lower-temp and cools faster, so some experimentation with the "crucible" would probably be in order. But that's home-brew for you.

Oh wow, I totally forgot I had one of those (the T Rex) growing up.

Ended up being one of my favorite bath toys.

Memories.

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