3DPrinting
3DPrinting is a place where makers of all skill levels and walks of life can learn about and discuss 3D printing and development of 3D printed parts and devices.
The r/functionalprint community is now located at: or !functionalprint@fedia.io
There are CAD communities available at: !cad@lemmy.world or !freecad@lemmy.ml
Rules
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No bigotry - including racism, sexism, ableism, homophobia, transphobia, or xenophobia. Code of Conduct.
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Be respectful, especially when disagreeing. Everyone should feel welcome here.
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No porn (NSFW prints are acceptable but must be marked NSFW)
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No Ads / Spamming / Guerrilla Marketing
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Do not create links to reddit
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If you see an issue please flag it
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No guns
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No injury gore posts
If you need an easy way to host pictures, https://catbox.moe/ may be an option. Be ethical about what you post and donate if you are able or use this a lot. It is just an individual hosting content, not a company. The image embedding syntax for Lemmy is 
Moderation policy: Light, mostly invisible
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Not exactly the densest material out there, but pennies are cheap and easily procured. May not be quite what you're looking for for your use case. (You asked about "cost/weight ratio" and "weight to space" which makes it sound like you're looking to add a lot of weight.)
I've been known to make a fully-enclosed cylindrical cavity and set my slicer to pause at exactly the right layer to where I can drop a few stacks of pennies into the print before upper layers seal the cavity closed.
You're creating a time capsule that someone will later discover and say "o shit, remember pennies?"