# molding?

Discussion in 'Off-Topic' started by Mathematics!, Jun 19, 2013.

1. ### Mathematics! Thread Starter Senior Member

Jul 21, 2008
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Metals, plastics and many other materials (concrete,mortor ,...etc) can be molded to any shape or design buy heating them to liquid form and cooling them to solid form in a particular mold.

But what I am confused about is where did we get the first molds from...
The process is pretty simple to understand provided you have the mold/design already...

My question is how did we get the infinite molds or another words how do we have a mold for every shape/design we want to make.

Seems like the chicken before the egg complex.

Since molding or having a mold plays so many parts in sculpting , designing, embroidering ,...etc
So I am very curious on the most important aspect of it all the actual mold itself

And today how does one obtain or create a new mold/molding design

2. ### Ron H AAC Fanatic!

Apr 14, 2005
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Molds can be made with hand tools and/or various combinations of power tools. The molds for cast metal statues were made by hand, from plaster, clay, wax, etc.
When I was a kid, I made a one-barrel to two-barrel carburetor adaptor from molten aluminum. I carved a positive from wood, made a negative (mold) with plaster of Paris, melted the aluminum in a hand-made furnace, and poured the metal into the mold. I used the adaptor on "my" '56 Chevy until my dad discovered it (he owned the car).

3. ### Mathematics! Thread Starter Senior Member

Jul 21, 2008
1,022
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Ya, forgot about etching/dremels and other electronics tools to do the mold design but before the discovery of electricity it must have been hard to mold as précises ... or at least it would take a hell of a lot longer.

4. ### THE_RB AAC Fanatic!

Feb 11, 2008
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I watch some of those ancient history type shows on the history channel.

Molding was used as far back as the copper/bronze ages. Probably first for small things like jewellery and belt buckles for horse bridles etc.

They showed an original mold for a bronze age sword, it was cut in stone. Pour molten bronze in, sword comes out.

It's pretty logical when you have something molten that hardens. Even on the smelters where the molten metal comes out they would dig a small trench in the dirt and pour the metal in it, later dug up and it's a ingot.

That's where the term "pig iron" comes from too, the mother trench would have little side trenches and the resulting ingots looked like a mother pig and suckling baby piglets.

So you can probably say molding is as old as melting?

Viking bronze jewellery casting in clay moulds;
http://web.comhem.se/vikingbronze/casting.htm

Last edited: Jun 19, 2013
5. ### GopherT AAC Fanatic!

Nov 23, 2012
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Molds (moulds) were originally carved by hand or made from a positive model by covering the original in plaster of Paris. With casting, everything can me done freehand, that is why brass artists love casting.

More difficult is actually the tools that cut straight lines. I want to know where the first straight edge came from two measure or guide a cut.

6. ### #12 Expert

Nov 30, 2010
16,670
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The method I am familiar with is called, "The lost wax process". A wax positive is made, then that is covered with something that will survive the heat. When this clay-like substance is "fired" to make it like a brick, the wax is destroyed. Then, the "precious" metal is poured into the hole the wax use to be in.

7. ### tracecom AAC Fanatic!

Apr 16, 2010
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Wow! I wish you had been my friend back then; I bet you could weld, too. You could have cut some holes in my exhaust pipes just behind the front wheels and welded on some "cut-outs."

Last edited: Jun 19, 2013
8. ### tracecom AAC Fanatic!

Apr 16, 2010
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That's a very interesting process...also called investment casting, I think. I did a brochure once for a company that did that. They used induction furnaces to melt the stainless steel.

9. ### tracecom AAC Fanatic!

Apr 16, 2010
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Years ago, I visited an exhibit (at the Smithsonian) that had huge cast iron, steam-powered machinery on display. I tried to imagine the process of creating the molds, casting the parts, and having everything fit together and work so precisely.

10. ### Markd77 Senior Member

Sep 7, 2009
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There are many methods. If it is a fairly simple shape you can make a 2 part mold using a positive original, separating the mold halves (can be sand with some oil to bind it together) and removing the original. For more complex shapes something like the lost wax method or a multipart mold is required. Back at school I made a cast by using expanded polystyrene as the positive and just pouring aluminium straight in, which vapourised / burned the polystyrene as the metal was being poured. Then there are methods that don't involve molten metal, like forging and sintering.

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11. ### #12 Expert

Nov 30, 2010
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A special thanks to Markd77. Some years ago, and I think it was on this forum, I suggested that any material can be used as the "wax" if it will be completely destroyed by the heat of the molten metal. I was firmly corrected (but I still didn't believe whomever it was that corrected me). I am quite happy to know that you actually did a lost wax process with another substance, and it worked.

12. ### shortbus AAC Fanatic!

Sep 30, 2009
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Much of the core work (the metal parts that are made in a casting) in modern car engine parts is done today by poly cores. In the past the mold was made of sand cores (that made the hollow part in a casting). This needed a hole to anchor the core to the out side of the finished part. Then they discovered the poly core mold technique, that allowed the making of parts without the anchor holes. Examples of the anchor holes are "freeze plug" holes in an engine block.

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