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So here’s a random idea I had.

Most readers are probably familiar with Dave Gingery’s series of books on building a set of homemade machine tools. The technique, basically, involves building an inexpensive homemade charcoal furnace and crucible for melting aluminum, then using traditional green-sand casting techniques to mold the various machine parts from wooden patterns. Much of the content of Gingery’s books details the construction of these patterns.

As I have recently discovered, however, lost-foam casting is a much more accessible metal-casting technique than traditional green-sand. It requires no special flasks, no special sand, and no consideration of parting-line placement in designing patterns. Basically you make your pattern from styrofoam, bury it in sand, and pour hot aluminum into it. The foam vaporizes and diffuses into the sand, and you’re left with a perfect aluminum duplicate. The only downside is that the pattern itself is destroyed, so if you screw up the casting or want more than one copy of a part you need a new pattern.

Here’s what I’d like to see: Some enterprising soul with a CNC foam cutter could sell kits of the Gingery machine patterns ready-cut in XPS foam.

Then, if you wanted to build the Gingery tools, you wouldn’t have to spend a lot of time learning the art of green-sand casting, or building the special tools required, or carpentering on the patterns themselves, most of which will only be used once anyway. You’d just buy a few ounces of pre-cut foam patterns in a kit, bury them in sand, and start pouring hot aluminum right away. Depending on sales volume, it might even be practical to make the foam patterns in conventional molds, the same way styrofoam packaging inserts are produced, at lower cost than CNC machining.

If you’re interested, supportive, or (for your own unfathomable reasons) furious, feel free to sound off in the comments.

Sean Michael Ragan

I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I write for MAKE, serve as Technical Editor for MAKE magazine, and develop original DIY content for Make: Projects.


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Comments

  1. Sprague says:

    That sounds like a good idea. I would purchase some foam forms!

  2. kdog says:

    Although building the molds, and patterns is obviously part of the “seriously, I did it ALL myself” experience”, some of the more complex parts are pretty intimidating.

    I would consider buying a set (or even two in case of screw ups, pending price). That is an awesome idea. Especially for (or even JUST for) the pulley assemblies.

  3. Todd says:

    I love this idea and would definitely purchase.

  4. DU says:

    A lot of the reason for building it yourself is to save money. Plus I don’t know about everyone else, but I’d be wary of screwing up a pour and having to re-buy parts. So the patterns would have to be pretty cheap.

  5. hiddentass says:

    It’s a great idea, but I think I’ll do most of it the hard way. For me, the project is more for the skill building — when I want to build attachments, or a different machine, I wont be able to get foam patterns for whatever weird thing I’m working on. Then I’ll need the green sand and pattern making skills. That said, being able to buy patterns for the many less interesting parts would be wonderful — perhaps a discount for the entire pack and a small premium for a la carte pieces.

    On a related note, while an argument could be made that selling your (whoever that is) interpretations of Gingery’s machine shop patters, I think I would be much more inclined to buy the parts if I knew a royalty of some sort was going to his family.

  6. Rob Logue says:

    I have the parts drawn up and saved in DXF file for the Lathe,Shaper and I believe the drill press if anyone is interested. Email me at jamielogue24@hotmail.com and I’ll round them up.

  7. PeterP says:

    Those would be very useful. DXF or Sketchup files would be nice as well.

  8. Andrew says:

    Anybody know how well the lost foam method comapres to the green sand/pattern method in terms of detail/finish? I now a big part of the lathe construction requires a lot of scraping, even with the green sand method. If a foam pattern is even rougher, it’ll take a lot longer to achieve the same results.

  9. Charles says:

    Sets would have to include extras incase there are casting problems or you would have to sell pieces individually so I could buy the ones that don’t turn out.

    Also it would be nice once the community grows to include new features like say a motor mount integrated into the bed foot.

  10. travis says:

    There are soooo many projects that could be started (or furthered) if there was a source for foam blanks. I’d use it just to finish my CNC project.
    Perhaps this is something that could be done using Ponoko.

  11. Dave says:

    This might work for the smaller parts, but the bed might not work well as a lost-foam casting. It’s pretty big and usually requires multiple steam holes.

  12. derek says:

    So many recent posts on metal casting. I smell a feature article in volume 21 or 22. I’m looking forward to it.

  13. Nathan says:

    Anyone know of what kind of chemicals are released when the foam is vaporised? Damaging to Lungs/Environment?

    I defintely WOULDNT subscribe to any service that produces new styrofoam objects.

    I would support reuse of styrofoam packaging to build these tools though.

  14. cdreid says:

    though you wont be able (as someone said) to use lost foam for the bed.

    Detail: Lost foam done right has much higher detail than sand casting. Using tape and spackle you can produce a stunning finish. Sand mold casting is good but the finish is what you think it is. Lost foam is more expensive (foam, spackle etc arent free) but less of a giant pita.

    Environmental concerns – not enough gas is produced to worry about it. If you stick your head over the hole you’re going to suck in some bad stuff but imho darwins law applies here

    This should NOT be done unless Gingerys family gets a cut. the man did this all free (or nearly so) and gave us a gift.

    BTW you dont have to use gingerys bed etc. I started constructing a lathe out of an old piece of Ibeam that made a FAR superior bed to aluminum. To those of you building it you should consider upsizing from the start and building a heavier,thicker, longer base.

  15. Northern DJ says:

    I built the lathe and tried building the molds out of wood and casting them in green sand. Lots of work, finished it using lost foam. The foam works great and is easy to use compared to the cavity molding. In the end the lathe works fine, but a set of foam for casting would be great for those who want to build the lathe and other machines but don’t have the time or wood working tools to make the molds. Contact the Gingery’s and see if they are interested in helping or even endorsing the project. Dave’s books helped me start working on metal casting, it has been a very satisfying and fun hobby. Good luck.

  16. Bill says:

    Anything that releases a styrene monomer (and I’m inclined to think vaporising a chunk of polymer, ie polystyrene, would do so…is EXTREMELY toxic!! Darwinian principles would certainly apply. I am no expert, but would seek clarification before I tried it around my kids.

    1. Sean Ragan says:

      Lost foam casting from styrofoam is a well-known technique. As in any metal casting operation, you need to be working with proper protective gear in a well-ventilated area, and, especially if you’re casting something as high-melting as aluminum, it’s not something I would be doing around young children in the first place. Your assumption that the process gives off styrene monomer in any significant amount does not seem reasonable to me, but don’t take my word for it: go read about the thermal decomposition products of polystyrene foam. Go look at the MSDS for styrene monomer to get a realistic idea of its toxicity and safe exposure limits. It is always prudent to err on the side of caution in setting up an operation and in choosing protective gear, but I hate to see chemophobia scare people away from trying something they might otherwise take enjoyment, learn, and/or profit from. Educate yourself and evaluate hazards rationally.

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