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The below shots will bring you up to date on the last two days work:
Both the single disc tool, used for metal casting and the other tools, used for resin casting comprised two-piece construction. The trick is to imbed the masters half-way in clay and to then pour the first half of rubber over the exposed portions of the masters. Here I've taken some of the masters off the cardboard I used to figure lay-out and have gotten them into the clay. The MDF mold-boards give a firm backing to the clay and the tape wrapped around the mold-boards forms a damn, or containment to hold the liquid rubber till it changes state to a solid.
The masters are pushed into the clay and a stiff brush (kept wet) is used to stipple the clay around the perimeter of each master to bring the clay up tight against their edges. The shank end of various sized drill bits are pushed into the clay to form a network of dimples that will materialize in the clay as positive indexing tits -- those tits will produce negatives in the second mold half which forms the indexing network that keeps the assembled tool halves in perfect registration to one another. I lightly scribe into the clay the feed and vent channels. The centrally running brass dowel will form the main sprue channel.
Once all masters are in place, stippled down tight into the clay and the feed and vent channels identified, the entire face of the retained masters and clay is given a coat of mold-release agent. The Mann 200 is perfect for this job, and it's also the stuff I used to prep the tool before each casting operation -- the stuff is great and extends tool life considerably when compared to other parting liquids I've tried.
Starting the pour of the first tool halves. The catalyzed rubber has been de-aired by subjecting the mix to a hard vacuum for several minutes -- a vital step for tools that will be subject to positive/negative air pressure and/or heat during the casting operation.
The blue rubber is TC-5050, available from BJB Inc. This stuff was used for the disc tool because this rubber ability to work at temperatures as high as 600 degrees. The Purple rubber is the more flexible and quicker curing Polytek 70-21 ... expensive as hell, but time is money in my shop.
One of the resin casting tools, only one-half of the tool did at this point, next to the masters and clay that gave its face form. The masters will be transferred to the rubber just as soon as the face and cavities of the tool is given a good shot of mold-release spray.
Pouring the second half of the disc tool.
Almost done with tool fabrication.
Finally! ... production parts! Here are some metal shots from the disc tool. I cast in white-metal, 95% Tin, 5% Antimony.
Molten metal is introduced through the central sprue hole only after the disc has been brought up to speed in this modified blood separation centrifuge. At the bottom of the shot, to the right is the metal melting pot. To the Left is a Moto-Tool speed controller I used to set the speed of the centrifuge.
Cast metal parts.
And assembled rudder foundation piece, to verify proper operation of the rudder linkage using production parts. Worked great, no problem. And some of the cast metal parts I produced today.
Both the single disc tool, used for metal casting and the other tools, used for resin casting comprised two-piece construction. The trick is to imbed the masters half-way in clay and to then pour the first half of rubber over the exposed portions of the masters. Here I've taken some of the masters off the cardboard I used to figure lay-out and have gotten them into the clay. The MDF mold-boards give a firm backing to the clay and the tape wrapped around the mold-boards forms a damn, or containment to hold the liquid rubber till it changes state to a solid.
The masters are pushed into the clay and a stiff brush (kept wet) is used to stipple the clay around the perimeter of each master to bring the clay up tight against their edges. The shank end of various sized drill bits are pushed into the clay to form a network of dimples that will materialize in the clay as positive indexing tits -- those tits will produce negatives in the second mold half which forms the indexing network that keeps the assembled tool halves in perfect registration to one another. I lightly scribe into the clay the feed and vent channels. The centrally running brass dowel will form the main sprue channel.
Once all masters are in place, stippled down tight into the clay and the feed and vent channels identified, the entire face of the retained masters and clay is given a coat of mold-release agent. The Mann 200 is perfect for this job, and it's also the stuff I used to prep the tool before each casting operation -- the stuff is great and extends tool life considerably when compared to other parting liquids I've tried.
Starting the pour of the first tool halves. The catalyzed rubber has been de-aired by subjecting the mix to a hard vacuum for several minutes -- a vital step for tools that will be subject to positive/negative air pressure and/or heat during the casting operation.
The blue rubber is TC-5050, available from BJB Inc. This stuff was used for the disc tool because this rubber ability to work at temperatures as high as 600 degrees. The Purple rubber is the more flexible and quicker curing Polytek 70-21 ... expensive as hell, but time is money in my shop.
One of the resin casting tools, only one-half of the tool did at this point, next to the masters and clay that gave its face form. The masters will be transferred to the rubber just as soon as the face and cavities of the tool is given a good shot of mold-release spray.
Pouring the second half of the disc tool.
Almost done with tool fabrication.
Finally! ... production parts! Here are some metal shots from the disc tool. I cast in white-metal, 95% Tin, 5% Antimony.
Molten metal is introduced through the central sprue hole only after the disc has been brought up to speed in this modified blood separation centrifuge. At the bottom of the shot, to the right is the metal melting pot. To the Left is a Moto-Tool speed controller I used to set the speed of the centrifuge.
Cast metal parts.
And assembled rudder foundation piece, to verify proper operation of the rudder linkage using production parts. Worked great, no problem. And some of the cast metal parts I produced today.
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