Question on permanent molds for aluminum

[CPS]

Hi,

I've been sand casting aluminum for several years. I'm to the point where I make the same 10-15 parts over and over (and over and over and over and over.....). If I could eliminate the time (which I consider wasted) where I ram up the mold and have to make another (and another and another and another.....) that would be great. I've posted a question in another section of the forum about a CNC foam mill to make my patterns, but I was also wondering if I should consider permanent molds. Some of the things I cast are extremely detailed, yet large enough that I don't think lost wax is a viable option. Plaster of paris and I don't get along, and I'm worried about it sticking to my part anyway. I'll try to post pics of the things I cast later, but what do you guys recommend I go with?

If you think I should do permanent molds, how should I make them? This is strictly for aluminum casting at this point.

Thanks for any help!
Craig

[Geof]

Originally Posted by CPS ..... Some of the things I cast are extremely detailed,.....Craig

You need to give an example of 'extremely detailed'. Some detail is possible in permanent mold casting also known as gravity diecasting; much greater detail is possible with pressure diecasting. It also depends on the alloy composition; some are more fluid when molten so you get better replication of fine detail but they may have properties that are nt suitable for your application. You need to spend a lot of time in a good library.

[CPS]

Here's a link to my website (which I haven't updated in a loooooong time). http://www.angelfire.com/pa5/casting/FG42project.html You can get an idea of what I'm working with here - it's a complex pattern to just lift out of the sand once it's rammed up. I usually have some stick to the pattern, and ruin some more by moving it around to loosen, and finally screw some more up when lifting out.

I do have a buddy with a machine shop, but I'm afraid when I show him this and tell him I need a 2 part steel mold made for it he'll either bash my skull in or tell me no problem, that'll be $4.5 million with half due before he starts.

The funny part about the whole deal is when I tell people I'm casting dummy guns - they're like 'oh....wow.....uh.....that's nice......' and then they're gone. I guess to some people guns are just too scary, even when they're solid aluminum and would make better clubs than guns lol.

Craig

[Geof]

Originally Posted by CPS ..........I do have a buddy with a machine shop, but I'm afraid when I show him this and tell him I need a 2 part steel mold made for it he'll either bash my skull in or tell me no problem, that'll be $4.5 million with half due before he starts.......Craig

I think that type of detail would be possible in a permanent mold; it is not very deep, just surface detail. But I suggest you wear a hardhat when you approach your buddy . $4.5 million is an overestimate; I think you can safely take 2 zeroes off; but taking a third zero off may not be possible.

[NC Cams]

PM's used to make automobile blocks and heads are constructed of H13 tool steel. Check it out for machining and heat treat characteristics.

The intricacy of the part to be cast is inter dependant on how and how well you cool the mold so it will "pull" away from the part being cast. Highly empirical process from what I saw when I visited many shops.

You might be better off, cost wise, with investment cast parts. Since the investment is merely wax and the molds aluminum, much less costly and easier to do for the beginner....

[Geof]

Originally Posted by NC Cams ....Highly empirical process from what I saw when I visited many shops.....

This is a fancy way of saying there is a lot of voodoo and magic involved; but correct.

What you might re-consider is lost foam but not by machining your pattern; expand your own pattern from the beads. To do it correctly requires fancy steam heated molds and things but I think with a bit of imagination you have a good chance of making something that will work. Aluminum molds are used and it is possible you could make yours by casting them. Use plaster to take a negative image from each side of the pattern you use for sand casting then use these plaster images as the pattern to make aluminum castings that will be the mold for expanding your EPS beads.

[CPS]

Obviously from my other post, I have been thinking of doing lost foam but did not know about expandable EPS beads - thanks! What suppliers have these and do you know of any websites showing their use? I built my equipment and learned all my procedures from the net and probably wouldn't even be casting without it, so I like to find as many websites as possible to help me along.

Craig

[Geof]

Originally Posted by CPS Obviously from my other post, I have been thinking of doing lost foam but did not know about expandable EPS beads - thanks! What suppliers have these and do you know of any websites showing their use? I built my equipment and learned all my procedures from the net and probably wouldn't even be casting without it, so I like to find as many websites as possible to help me along. Craig

Just Google lost foam casting or EPS foam and you will get buried with links.

[gregsnovas]

this guy has some great ways of doing things

http://www.buildyouridea.com/foundry.html

[epineh]

Nice work, have you thought of using a diy cnc machine to do the same thing, I'm not saying it would be an easy option but you would get great repeatability, not to mention all of the other stuff you could use the machine for...

Russell.