Back about 1990 we built a mold for a fuel cap for a tractor that used a collapsible core like that. Worked great. What amazed me is it's just a two piece unit, the center round pin and the outer segmented collapsible core. The segmented fingers are all machined from one piece of steel with slots between the fingers to allow them to spring and collapse. What I always wanted to know is how they got the segments ground in between with it being one piece. If it's not a trade secret, I'd love to see how they manufacture the cores.
You can insert a larger plug in the middle or something between the fingers to spread them and then grind with a very narrow edged wheel. But have to careful, as the geometry is a bit different when it is collapsed vs. spread out.
We have a mold in our shop now that uses collapsible cores just like this; finnicky things, but they're great when you have everything dialed in. Much better and cheaper than a hydraulic "un-threading" mechanism.
Can this type of core be used in die casting aluminum? We are trying to eliminate a machined undercut in a cavity bore, and have the undercut as cast. Thanks!
A fine example of many people doing excellent work to produce a necessary part that most of us take for granted. Thanks!
Seriously 😢
Back about 1990 we built a mold for a fuel cap for a tractor that used a collapsible core like that. Worked great. What amazed me is it's just a two piece unit, the center round pin and the outer segmented collapsible core. The segmented fingers are all machined from one piece of steel with slots between the fingers to allow them to spring and collapse.
What I always wanted to know is how they got the segments ground in between with it being one piece. If it's not a trade secret, I'd love to see how they manufacture the cores.
You can insert a larger plug in the middle or something between the fingers to spread them and then grind with a very narrow edged wheel. But have to careful, as the geometry is a bit different when it is collapsed vs. spread out.
Always talking about these, good to see how they actually work. Great video!
We have a mold in our shop now that uses collapsible cores just like this; finnicky things, but they're great when you have everything dialed in. Much better and cheaper than a hydraulic "un-threading" mechanism.
Brilliant example of collapsible core threads. Thanks for sharing. 🍻
Please continue Mold-making Lessons. Don't stop teaching/passing knowledge.
Thanks for the help. Working on one now. Happens to be from DME as well
Thank you for posting such instructive content !
Very interesting. Thanks for the content.
Very cool Phil. good stuff
Interesting as usual Phil.
Strangely enough, I instantly recognized it from my 20 years in the Navy.
My father designed the mold for Kiwi shoe polish caps that were threaded back in the 70's
Much gratitude on valuable information
Nice video...please note that they are build by Roehr, not DME...
Can this type of core be used in die casting aluminum? We are trying to eliminate a machined undercut in a cavity bore, and have the undercut as cast. Thanks!
Did you succeed ?
Good design, we could make it, if you need any Collapsible Cores or mold, please feel free to contact us.
Thanks for ur nice class. It's really useful for me.... thanks... thanks... thanks
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What is the material type of core. I wonder what kind of heat treatment is applied. can you help me?
Vaccum hardening..to avoid destrortion
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sort of an anti-expandable mandrel