Metal Casting: Tips and tricks! (MODS Please Archive!)

Discussion in 'Replica Props' started by Rook 3, Apr 23, 2003.

  1. Rook 3

    Rook 3 Sr Member RPF PREMIUM MEMBER

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    A while back we had a thread that was started by Hydin, a thread that asked several questions about how to cast items in metal.

    Several people (I can only remember Theatrix and Megatron?) posted personal experiences and suggestions on what to do and NOT do, as well as safety concerns/experiences.

    And despite repeated requests to archive the thread, it's gone now and the information is lost.

    SOOoo... I propose that those in the know please offer their insights again.

    Web links to materials or pre-existing tutorials are a plus.

    Thanks in advance,

    Rook
     
  2. hydin

    hydin Sr Member RPF PREMIUM MEMBER

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    yea [​IMG]

    i looked for it when i got back to the board, and apparently a thread that has a lot of information in it isnt worth archiving.

    maybe we can start up a new one though, specially since i still dont have any metal casting equipment [​IMG]

    chris
     
  3. replicaprops

    replicaprops Official Licensee RPF PREMIUM MEMBER

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    I have been fooling with metal casting for a little while.
    I did a few parts in lead from old fishing weights.

    I think the best info source on this topic has been www.backyardmetalcasting.com

    I have personaly been attempting lost wax casting. I have had some good success with this when I did a vader shroud and some other parts.
    Sand casting seems like its made for large objects rather than small detailed parts.

    I can tell you that in lost wax casting, you should use the wax made for the process. Candle wax does not burn out clean enough to make a good cast. Also, if your doing anything hotter than 600 degrees use the proper mixture of plaster and sand, The plaster of paris I used tends to get very brittle when burning out the wax.
     
  4. Scott

    Scott New Member

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    The wax casting, I believe, is what you see in the prologue of LotR, just FYI. [​IMG]
     
  5. Xeno Kenobi

    Xeno Kenobi New Member

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    I heard from 5postboy that sand is what they use for molds. For High Quality Industrial molds use metal.
     
  6. Rook 3

    Rook 3 Sr Member RPF PREMIUM MEMBER

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    Here's a couple of the sources that were listed in the last discussion.

    I found them while crawling through the mountain of forgotten links in my own archives. [​IMG]

    Metal Casting Supplies

    http://www.miniaturemolds.com/mainframe.htm

    They sell a 20/1 by weight RTV siliconewith a max temprature
    of about 700 degrees, which should be good for casting pewter.

    The small-ish kit (2.2 lbs) is about $45 for the silicone and catalyst.

    Other Metal Casting Supplies Sources

    http://www.imperialinfo.com/sca/pewter.htm

    Metal Casting Tutorial

    By Theatrix.

    http://home.att.net/~tk1066/Casting.htm

    Enjoy!

    Rook
     
  7. TK2692

    TK2692 New Member

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    The Theatrix tutorial you are looking for the link to is the last link in your post.

    TK-2692
     
  8. CJP

    CJP Well-Known Member

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    What's the typical shrinkage rate when casting with metal?

    Chris
     
  9. Cyland Props

    Cyland Props New Member

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    I learned lost wax casting in High School along with aluminum casting, now 14+ years ago ouch! For lost wax casting you want to use investing compound which is a fine grain powder that doesn't shrink with heat and doesn't retain water like plaster. I've always wanted to run into a centrifugal caster at a swapmeet so I could do some killer casts.

    For white metals the silicone mold method will work well when you make the mold walls real thick to hold the weight of the metal. Basically the same things used for resin casting is followed. Powder the molds with talc, wire the molds shut or make a metal box to go around it and heat the molds before casting. As for shrinkage the parts tend to expand do to the weight and cooling. For a vader shroud (rotj) I made, the inside shrunk back about a 1/16" so the hole instead of being 1 1/2" it was now 1 5/8"
     
  10. Rook 3

    Rook 3 Sr Member RPF PREMIUM MEMBER

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    How many white metal casts can you do in a row before you start damaging the mold?

    Is there a certain length of time you should wait between pours?

    Rook
     
  11. theatrix

    theatrix Member RPF PREMIUM MEMBER

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    </SPAN><TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD CLASS=$row_color>
    Rook 3 wrote:
    <HR></TD></TR><TR><TD CLASS=$row_color>
    How many white metal casts can you do in a row before you start damaging the mold?

    Is there a certain length of time you should wait between pours?

    Rook
    </TD></TR><TR><TD><HR></TD></TR></TABLE><SPAN CLASS=$row_color>

    We did approx 1000 castings in 2 molds of 3 copies/positions each. The molds showed little or no deterioration. Regarding how long to wait, I first dust the molds with graphite, rub it in and then start casting. Normally, we get around 5-10 sets of castings from the Silicone RTV (platinum catalyzed) before they molds are "too hot". We then set aside the warm mold and switched over to the cool one. Repeat as needed.

    How hot the mold gets depends greatly on how large the cast object is. You can tell the molds are getting too warm for good casting by touch (i.e. how warm they feel through the gloves) and by the fact that the silicone molds start to deflect (i.e. edges don't line up right).

    Also, this only applies to the 2 part platinum catalyzed silicone RTV that we use a lot. Other silicone/vulcanized materials can behave differently.
     
  12. phase pistol

    phase pistol Master Member RPF PREMIUM MEMBER

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    How can it be the "lost" wax method if YOU guys know how to do it... [​IMG]

    - Karl
     
  13. WolfMorganFX

    WolfMorganFX New Member

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    Here's my metal casting set up... [​IMG] Cheap & easy, everything from Home Depot...

    I use the same silicone molds I use for my resin pieces, & a propane torch for the heat source... All you have to do is liberaly coat the molds with talcum powder, & prewarm them for about a minute in the microwave...


    [​IMG]

    My crucible, a 1.5" copper endcap, with a dowel handle screwed to the side, the base is a wood block with an old CPU heatsink...
    [​IMG]

    1# roll of silver alloy plumbers solder, solid wire ( No flux!!!) About $12 a pound... This stuff is excellent, & make a very strong, solid casting, that cleans up beautifuly... Looks just like pewter or sterling silver...
    [​IMG]

    Examples, you can do both small & large castings with this setup, with excellent detail... [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]


    Any questions, feel free to ask...


    Wolf
     
  14. Dusza Beben

    Dusza Beben New Member

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    Would an open face mold made of high fire ceramic (stoneware) work for casting small items in metal? I want to cast my Naboo SOG emblem (Below left in my banner) for use on my armor and as a hat insignia. Sculpting it is no problem. And I've got a kiln and plenty of clay.

    DB

    (edit; clarified [ I Hope [​IMG]] )
     
  15. kimncris

    kimncris Well-Known Member

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    I tried silver solder a couple of times, but I found that I got much better detail using Kurt's SFProps brand metal.

    Otherwise I pretty much do the same thing as above, melting the metal right in the ladle (stainless food ladle) with a propane torch and pouring into regular old silicone molds.

    -cris
     
  16. Rook 3

    Rook 3 Sr Member RPF PREMIUM MEMBER

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    Do you have to re-dust the molds after every pull, or can you do a couple before needing to re-dust?

    Where do you get "Kurt's SFProps brand metal?" Cost/weight?

    The "pewter" metal from miniaturemolds.com is about $7.00/10oz

    Rook
     
  17. WolfMorganFX

    WolfMorganFX New Member

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    The medallion would be a snap to cast, but a silicone mold is your best bet... I think a clay mold would pretty much be a one shot deal, like casting into plaster molds...
    I dust my molds before every pour, keeps them from burning out or losing detail to quickly...
    The other solder I use is the 60/40 tin/lead solid wire... It's esentialy the same mix as the casting ingots, & it works extremely well for crisp detail, & costs less than the silver solder... I use both, depending on the castings I'm doing... I've found the tin/lead mix tends to burn out quicker than the silver when remelting scrap pieces or bad casts (meaning the castings get duller & more brittle, & often have more flaws)... Occationaly I'll mix them half & half, to revitalize remelted pieces... I also clean the slag off with pretty much every use, so it keeps the impurities to a minimum...


    Wolf
     
  18. Emuyshondt

    Emuyshondt New Member

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    What is best to dust the molds with? Talcum Powder, or this Graphite powder I read about? (Had never heard of graphite powder before).

    Are there any particular pros and cons to using one or the other?

    Where could graphite powder be bought?

    Also, do you dust the molds after each use (I'd assume so), or as needed?

    Does anyone here know the heat tolerances of Smooth-On Mold Max and Oomoo series silicones?

    A lot of questions, I appreciate the help of you all though.

    Thanks! [​IMG]

    -EM
     
  19. Emuyshondt

    Emuyshondt New Member

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  20. kimncris

    kimncris Well-Known Member

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    </SPAN><TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD CLASS=$row_color>
    Rook 3 wrote:
    <HR></TD></TR><TR><TD CLASS=$row_color>
    Do you have to re-dust the molds after every pull, or can you do a couple before needing to re-dust?

    Where do you get "Kurt's SFProps brand metal?" Cost/weight?

    The "pewter" metal from miniaturemolds.com is about $7.00/10oz

    Rook

    </TD></TR><TR><TD><HR></TD></TR></TABLE><SPAN CLASS=$row_color>

    I found it best to "dust" with dust made from the same metal I was casting (just rub on some sandpaper) and I did it every time.

    Try PM'ing SFProps about his particular formulation. I think it was about $11 per pound. He used to do a bulk order now and again.

    Like I said, I found it very easy to work with.

    -cris
     
  21. kimncris

    kimncris Well-Known Member

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    BTW, here's an example of how the cast's turned out and how they looked polished.

    [​IMG]

    another

    [​IMG]

    -cris
     
  22. Rook 3

    Rook 3 Sr Member RPF PREMIUM MEMBER

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    Wolfmorgan said...

    </SPAN><TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD CLASS=$row_color>Quote:<HR></TD></TR><TR><TD CLASS=$row_color>I also clean the slag off with pretty much every use, so it keeps the impurities to a minimum...
    </TD></TR><TR><TD><HR></TD></TR></TABLE><SPAN CLASS=$row_color>

    How do you do this? Is there a special tool, or just a certain technique?

    Rook
     
  23. kimncris

    kimncris Well-Known Member

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    I use a popcicle stick. Boring I know [​IMG]

    -cris
     
  24. Rook 3

    Rook 3 Sr Member RPF PREMIUM MEMBER

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    LOL! See, it's little tips of the trade like that that are helpful!!

    Thanks!

    Rook
     
  25. Gytheran

    Gytheran Sr Member

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    Iteresting... how well does this stuff work for larger applications? How soft is the metal when done?

    Joe
     
  26. kimncris

    kimncris Well-Known Member

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    That gun stock butt-plate was the largest thing I've made. That particular metal is VERY hard and somwhat brittle. It won't shatter or anything like resin, but it's not at all bendy either.

    -cris
     
  27. SFPROPS

    SFPROPS Well-Known Member

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    FYI: The stuff I get in bulk from a foundry, but I've got my "prop budget" tied up in a few other projects so I don't know when I'll be able to get together another big order so that it's cheap (compared to other sources). The metal in question is the same forumulation that Micro Mark sells as it's "280" casting metal. I think that the price Cris quoted was about right...the bigger quantity I get though the cheaper I can sell it.

    As far as the "slag" (sometimes refered to as "dross") goes, it's a by-product of heating the metal. As it gets hot, impurities float to the top forming a light "crust" layer. I just scoop it off with an old spoon and toss it in an old coffee can. Usually, I'll do that twice before the metal is hot enough, and ready to pour.

    I usually just use baby powder on the molds. I've got an old sock filled with baby powder, with the top tied off that I tap against the inside of the mold then tap out any excess. At least for the metal I've used, in silicone molds, you HAVE TO powder your molds or the surface of your metal will come out pitted with small pours. Cris's idea of using the fine metal shavings sounds ingenious. I'll have to try that sometime.

    When fully cooled, the metal is pretty hard. Much harder then lead and most regular pewters. It's about as solid as resin, but with a lot more mass so it doesn't seem quite as fragile,
     
  28. Rook 3

    Rook 3 Sr Member RPF PREMIUM MEMBER

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    </SPAN><TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD CLASS=$row_color>Quote:<HR></TD></TR><TR><TD CLASS=$row_color>
    Type 280. Tin/bismuth alloy; lead and cadmium free. Melts at approx. 280ƒF. Can be melted with small butane torch. One 11.4 oz. bar (approx. 3/4 inch x 1-1/2 inches x 1-7/8 inches)

    Type R.(also the same metal that 'Miniaturemold.com calls it's 'PS1') Lead-free Crown Pewter (92% tin). Melts at approx. 575 degrees F. Can be melted with propane torch (plumbing type torch sold at hardware stores). One 21 oz. bar (approx. 1-1/2 inches x 1-5/8 inches x 2 inches).

    Note: Molds last longer when used with Type 160 or Type 280 alloys.
    </TD></TR><TR><TD><HR></TD></TR></TABLE><SPAN CLASS=$row_color>

    Info quoted from Micromark's web site. [​IMG]

    Rook
     
  29. Gytheran

    Gytheran Sr Member

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    Cris, btw, I can't see your pics. Is one of those the stock?

    Joe

    *edit
    cool I can see them now. [​IMG]
     
  30. kimncris

    kimncris Well-Known Member

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    really? My pics aren't showing up?

    the pic is just the butt-plate thing. Not the whole stock.


    -cris
     
  31. Gytheran

    Gytheran Sr Member

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    for whatever reason they aren't showing up for me


    Joe
     
  32. kimncris

    kimncris Well-Known Member

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  33. Gytheran

    Gytheran Sr Member

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  34. kimncris

    kimncris Well-Known Member

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    that is so wierd. I can see the pics and use the links too. I'll have to ask my webhosting friend about that.

    -cris
     
  35. WolfMorganFX

    WolfMorganFX New Member

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    The pieces I've made are extremely tough... They feel like cast aluminum, but perhaps a little heavier. they don't bend, & I haven't broken any yet...
    The belt buckle shown about is about 1/8" thick, 1/16" in the grooves, & I can't bend it... maby if I clamped in in my vise & put my whole weight into it... [​IMG]

    LOL & I use the popsicle sticks as well... [​IMG]


    Wolf
     
  36. theatrix

    theatrix Member RPF PREMIUM MEMBER

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    I get the OR-8 alloy for around $4.60 a pound with similar prices for the aquaclean (a silver bearing alloy). Both are lead free and work well with the Silicon RTV. Regarding strength, we have cast a lot of medallions, from 1/16 (and thinner) to over 1/4 thickness. While the thinner pieces can be bent, anything over 3/32 to 1/8 is pretty darn sturdy. It certainly can take more abuse than resin, however it does weigh more than aluminum (based on approximations from use).

    My ladle has a small extension for skimming the dross. I also wear a full catridge respirator when casting as the fine particles from the metal (especially when skimming) can get inhaled and it will stay with you. You can also make a "L" shaped "scoop" out of a larger nail (hammered and dished a bit), then clip and hammer one end into a piece of spare scrap wood cut to size (it was one of my first hand built tools).

    Regarding graphite, I buy mine from the same place I buy my silicone. I also only dust the molds as I rotate them or I notice pitting on the surface of the castings. With a properly dusted mold you can acheive near mirror finishes right out of the mold.
     
  37. Rook 3

    Rook 3 Sr Member RPF PREMIUM MEMBER

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    What are the melt characteristics of the OR-8 and Aquaclean?

    Melt temprature I mean. Is the strength you describe common between the 2 different metals?

    And, where can you order it from?

    Thanks !

    Rook
     
  38. theatrix

    theatrix Member RPF PREMIUM MEMBER

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    The optimum melting temperatures for OR-8 and Aquaclean are approx 580 degrees F. Yes, they both have approx the same strength. OR-8 is alloyed for strength, finish and it fills detail well. So does Aquaclean, but it costs a bit more due to is silver bearing alloy (only around .5 percent).

    I buy mine from Conquest Industries in Santa Fe Springs, CA.

    www.conquestind.com

    They are a subsidiary of Fry Metals. You can probably also find that Tin/Bismuth alloy at a much better cost than through MicroMark and other resellers. Conquest sells great amounts of both lead bearing and non-lead bearing alloys, solders and pewter each month to large productions houses in the So Cal area, so their prices are very good.

    They prices I get are a bit ($4 ish) are lower as I buy around 50 to 100 pounds at a time and I have bought from them in the past. However, even their full price is only around $6.00 per pound (in 5 pound bars). They also have plate stock in lead free pewters.
     
  39. theatrix

    theatrix Member RPF PREMIUM MEMBER

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    FYI-

    I spoke with Joe up at Conquest (he is the Sale Rep I work with). They carry the Tin/Bismuth alloy for approx $7.25 per pound. It is called 4258 in the Fry/Conquest catalog for its alloy composition:

    Tin - 42 percent Bismuth - 58 percent

    It casts at 281 degrees. He also said that it was crap for spin casting as takes a long time to set up vs other alloys. However, it is fine for "one-off"/gravity casting as we can leave it in the molds longer. It is just not that well liked by large volume/fast production folks.

    He also said that it is used a lot for Oncology work. They make some sort of shield for use during cancer treatment (you would have to ask him for details).

    Anyway, if folks are interested, I could pick some up. I can probably get it cheaper than the $7.25/pound since I buy in bulk from them pretty often. Also, if we did a bulk order, I could pick it up and then ship out bars for folks. I did that for a few folks a couple months ago for some OR-8 and Aquaclean.

    If you want to buy it yourself, here is their contact info:

    Conquest Industries
    9915 Bell Ranch Drive, Santa Fe Springs, CA 90670
    Phone (800) 368-2278 Fax (562) 906-1112

    Ask for Joe in sales.

    Tim Knapp
     
  40. Rook 3

    Rook 3 Sr Member RPF PREMIUM MEMBER

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    Boy, I was gravitating away from the higher temp stuff, but now I'm not so sure.

    Assuming I go with the OR-8, and I powder/graphite the mold well, any idea how many casts I could get before the mold becomes damaged?

    The parts I want to do are mostly internal re-enforcing parts (model gun parts) but potentially I could also do a trigger, mag release and a hammer, so theose parts will see some use, not "real world" use though.

    Thanks for all the info everyone!

    Rook
     
  41. hydin

    hydin Sr Member RPF PREMIUM MEMBER

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    still, the cheapest metal melter ive found for the high temp stuff was that one on lurecraft.com . if it can melt lead (something like 900 degrees), itll handle the smaller stuff too. a 10 pound melter was something like 50 bucks. not too shabby.

    ive got an idea forming, but i gotta ask a few more questions before i start up on the whole thing.....

    chris
     
  42. Emuyshondt

    Emuyshondt New Member

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    A bit of an "extension" to what Hydin said, I'm building a small metal casting furnace at the moment, will run on charcoal.

    If it works I'll let you know how it turns out - it's supposed to be able to melt aluminum and bronze. So, it should be hot enough to cast most practical metals.
     
  43. Rook 3

    Rook 3 Sr Member RPF PREMIUM MEMBER

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    Depending on how large of a thing you need to make, it seems you can just melt the metal in your ladle using a standard plumbing propane torch.

    Rook
     
  44. theatrix

    theatrix Member RPF PREMIUM MEMBER

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    Mold Damage is going to depend on a number of factors including, but not limited to:

    1) How thick you make your mold walls. If your mold walls are too thin, they are very "wobbly". Also in my earlier molds (when I tried to go cheap on silicone), the molds would start to tear from the outer edges (mostly near the thinest spots).

    2) How big your parts you are casting are. The bigger the part, the more heat that is radiated from the metal into the silicone. I have done hundreds of 50 cent sized by 1/8 or so castings from a single mold. Thousands out of a group of molds made for mass production (using platinum catalyzed silicone). I had one mold that was approx 2 inches across and about 3/8 thick. The mold lasted for about 13 copies before its consistancy turned to that of thick jello on the obverse and reverse sides. I am not sure if this was due to how much heat came out of the casting or because the metal was just too hot (this was before I got a metal temp thermometer).

    3) How hot you get the molten metal in relation to your silicones optimum casting temperature. For example at 580 degrees and by rotating molds, I can get hundreds of castings from one mold (with 3 positions each). At over that I have had molds turn "gooey" (see #2). Having a good thermometer and keeping track of your mold materials, alloys and casting temperatures will help you figure out what works best for each alloy and mold material.

    4) While you can mold some small undercuts in models using silicone rubber molds, they will decrease the mold life. With any undercut, it is eventually going to tear out due to the repeated removing of parts from a mold that wants to lock the part in.


    Regarding Melting alloys, what you use depends on your finances and what you regularly cast.

    I have seen or used the following to melt pewter and/or lead (before I knew better in the 70's):

    A metal pot on an electric stove/hot plate or a gas burner

    Hand torches to melt the metal in a ladle, can, crucible, or even a spoon.

    Iron pots over coals

    Electric melting pots (i.e. Lee Pots/other similar brands)

    Melting metal directly in the throat/spru of a mold with a torch and then using steam to inject the metal into the mold.

    From my experience, the advantage of electrical melting pots is that you can bring your alloy to its optimum temperature and hold it there for extended periods of time without much muss and fuss. When I have used torches, I felt like I needed to be an "octopus" to manipulate molds, ladles and torches effectively. It is nice to have a "helper" to hold the torch for you so you can just bring the ladle filled with solid metal into contact with it. Once you reach your casting temp, you can focus on making a good pour while your buddy tends to the torch. You can also clamp the torch in place, but I prefer to have someone in control of it. Just my foible. It really boils down to what you are comfortable with and what you prefer to use.

    I like electric pots that I can keep large amounts of metal molten at a fairly constant temperature for doing BIG runs of items (hundreds at a sitting). Also, by using an electric pots, I can keep my metal from oxidizing too quickly (yes, pewter does oxidize, where do you think all that dross comes from). You can help keep dross from forming by not over heating your metal and by not stiring it up too much (turbulence can excellerant dross formation, but in the pot and while casting). So don't whip your ladle around in the pot too much and pour your castings in a nice smooth manner (i.e. not straight down your spru).

    Finally, you don't need a big elaborate set up. You can melt pewter on a hot plate in a aluminum measuring cup. For around $20.00 you can buy a 2 pound electric pot. For under a hundred and twenty five you can buy a big 5 or 10 pound pot, a good ladle and a good metal thermometer. Also, the electric pots I have can run up to around 900 or so. Though I almost never go above 700 (with high tin alloys for very thin castings in soap stone molds).
     
  45. theatrix

    theatrix Member RPF PREMIUM MEMBER

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    FYI -

    The low temp alloys can work just fine for making hobby parts like we would use on a prop. They just don't work so well for spin casting in "high production" situations where you want to de-mold quickly and prep/cast a new mold fast.

    For casting parts for a prop, the 280 alloy (i.e. the 4258 Tin/Bismuth) should work just fine. In addition, with the lower working temperature of only 281 degrees, you can cast in lower temp silicone (which is less expensive). You could even cast in a paper mold as it burns at 451 degrees (thank you Ray Bradbury for never letting me forget that one).
     
  46. theatrix

    theatrix Member RPF PREMIUM MEMBER

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    </SPAN><TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD CLASS=$row_color>
    hydin wrote:
    <HR></TD></TR><TR><TD CLASS=$row_color>
    still, the cheapest metal melter ive found for the high temp stuff was that one on lurecraft.com . if it can melt lead (something like 900 degrees), itll handle the smaller stuff too. a 10 pound melter was something like 50 bucks. not too shabby.
    </TD></TR><TR><TD><HR></TD></TR></TABLE><SPAN CLASS=$row_color>

    Depending on what you need to cast, you can buy a Lee 2 pound pot for around $20. However, I like my large 10 pound pot since I can put an entire 5 pound bar into it to melt at once. With my little 2 pound pot, I had to cut it into little chunks with a hacksaw, what a pain in the bu#%.

    I guess you could also use a torch to section up a big bar, but I didn't have one at the time.
     
  47. SFPROPS

    SFPROPS Well-Known Member

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    </SPAN><TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD CLASS=$row_color>
    theatrix wrote:
    <HR></TD></TR><TR><TD CLASS=$row_color>
    The low temp alloys can work just fine for making hobby parts like we would use on a prop. They just don't work so well for spin casting in "high production" situations where you want to de-mold quickly and prep/cast a new mold fast.
    </TD></TR><TR><TD><HR></TD></TR></TABLE><SPAN CLASS=$row_color>

    I agree. The 280 stuff would be crap for spin-casting. You've got to keep your molds still while it sets up. The metal hardens slowly from the outside in (I'd say a piece the size of a trigger would take about 4 minutes to demold...bigger pieces would take longer). If you jar the mold while it's cooling, the hot metal on the inside can push outward toward the outside and you'll end up with a pitted surface. Unless you're planning on doing hollow casts or spin-casting, it shouldn't be a problem though.

    I've heard good stuff concerning the Aquaclean as well, but haven't gotten to try it. It you don't mind the extra temperatures (even working with 280 can leave you with scars...I'm living proof) and aren't planning to paint your pieces but rather leave them bare polished metal, that might be the way to go. I've seen highly polished pieces made from that stuff and it looks great and seems to require less finishing work than the 280 to give it a "plated" look.
     
  48. Rook 3

    Rook 3 Sr Member RPF PREMIUM MEMBER

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    What kind of de-mold time are we looking at for small parts (say, under 2 oz of metal)?

    5 minutes?

    Room
     
  49. theatrix

    theatrix Member RPF PREMIUM MEMBER

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    </SPAN><TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD CLASS=$row_color>
    Rook 3 wrote:
    <HR></TD></TR><TR><TD CLASS=$row_color>
    What kind of de-mold time are we looking at for small parts (say, under 2 oz of metal)?

    5 minutes?
    </TD></TR><TR><TD><HR></TD></TR></TABLE><SPAN CLASS=$row_color>

    For our largest medellions, using OR-8, we were able to de-mold in under a minute. I haven't ever timed how long to de-mold, but with both OR-8 and Aquaclean, they set up pretty darn fast in Silicone RTV, Soapstone, Charcoal and plaster molds. They only time I have had to wait very long times to de-mold is when I do medieval period castings using 2 pieces of cuttle fish bone. The cuttle fish bone acts like a big thermos and the heat can't radiate away quickly. I have had buttons and stuff take minutes to finally "chill"/set up.

    One way to get cuttle fish bone cast parts to set up more quickly is to us a soapstone back on the reverse and the cuttle fish bone on the obverse (front). The soapstone helps to radiate away the heat very quickly.
     
  50. MDKronos

    MDKronos New Member

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    Scott, I don't want to come across as a know-it-all since the only posts I make are corrections, BUT when Sauron is casting the one ring, metal is being poured into a cuttlefish bone mold. It's a really cool technique, not great for fine detail as there is a strong tendancy for the casting to pick up the growth lines in the bone creating a wood-grain type effect. I laughed out loud in the theater when I saw that, thinking of all of the clean-up Sauron would have to do to make that ring look pretty. My wife was not pleased.
     

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