G+yellow, slot3, and castings

https://drive.google.com/file/d/0BzapArv08I07dWZjSnRNY0g4TWc/view?usp=sharing

Printed, molded in Mold Max 60, cast in lead free pewter. Flush set chrome diopsides.
4 layers @20000ms, remaining layers @6000ms. 50um layers. 


Comments

  • rkundlarkundla Member, Moderator, Backers, Ultimate Backer
    edited December 2015
    @Gary did you use lost wax with your pewter casting or sand/delft/other?

    It looks like you lost some of your resolution in the final output. Was that due to the molding or the casting?

    What are the dimension of your print? That is a very interesting medallion, is there a story behind it?


    Ron
  • GaryGary Member, Backers
    I've done both sand and silicone mold castings - these are from a silicone mold gravity poured. I'm still working on process.
    The sand castings actually had better overall resolution and nice texture. Downside is the mess and time involved for single pour molds. 

    The silicone mold looks good - there could be a lot of reasons for the fidelity loss in the final casts. I almost always get deformation/shrinkage at the bottom of the sprue There are lots of variables. I didn't cut any vents in the silicon molds. I'm not sure how much resolution to expect from gravity poured castings. Also these are about as thin as I can expect to go. The thickest area is 2.7mm. The details are raised about .8mm. 

    I'm not set up for centrifugal casts or investment burn outs. Might wind up heading in that direction.

    The design was inspired by a couple of pre/adolescent witch wannabes. A pentagram surrounded by 13 little maidens :)
  • rkundlarkundla Member, Moderator, Backers, Ultimate Backer
    I think centrifugal casting is your best bet for this type of object to consistently get the fine detail. Nothing like hot spinning metal to make your work a little more exciting! ;)

    For gravity with silicone? My first thought would have been that you need the face of the medallion to face downward to allow gravity to pull all the metal into the fine detail. Having the sprue on the back would better serve the metal supply for the medallion, but the mold won't support that, or can it?

    You probably also need a longer sprue to help provide a source of molten metal to deal with the shrinkage. Kind of what we do with the investment casting and the button of extra metal so as the metal cools it doesn't try to draw it from the item being cast.
    Ron
  • Joseph_OsbornJoseph_Osborn Member, Backers
    Gary, make sure you're using talc in that silicone mold so that the hot metal flows in there nice & easy.
  • GaryGary Member, Backers
    @ron Centrifugal or vacuum casting would surely improve results, as well as a much larger sprue - i'm printing up a pattern with a big sprue now. If course, the downside is using a lot more expensive silicone for the mold.

    @josepd_osborn -- The mold has been seasoned with acetylene soot, but I can certainly try a baby powder dusting. Works for sand, can't think why it shouldn't with silicone. I have tried a graphite spray, but it didn't work as well as the soot.

    I played with a plaster of paris mold today, and apart from having trouble releasing the model, and then releasing the casting, the results looked very good. Cast with the mold just out of a 450F oven. 

    My first molds were side pour - and I got good detail - but demolding was a real pain as the casting winds up pinned to one side of the mold by the sprue and vent. No problem for a throw away mold, but an issue for a re-usable one.

    The items I plan to model are not intended to be high end, but rather $20-30 range ornaments targeted at beaders or the etsy/artfire customer. multiple castings per mold are a necessity. doing oneseys  works much better for sterling, fine, and gold, for customers who will pay for them. But those customers are hard to find on a consistent basis!

    bare minimum of finishing - sanded edges, brushed surfaces. I'll put up a pic of the new model/sprue design in a couple of days after I've got a successful print/mold/casting. 
  • GaryGary Member, Backers
    Modified model with bigger button and vents.

    The new model take almost twice as much silicone to mold due mostly to the increased depth.


    Getting better detail, but still not as good as a forced cast would produce, but plenty good for my needs.

    Ready for stone setting:

    talc worked fine as a mold lubricant for casting, but soot works even a little better. a graphite spray did not work as well.



  • rkundlarkundla Member, Moderator, Backers, Ultimate Backer
    Wow, significant improvement in detail in my opinion! The crosses are way more detailed than the previous version, so I'd say it was a winner.
    Ron
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