I can’t find something more economical than pennies! I think I am taking crazy pills or something, how is this possible?
Pennies are 11c / oz or 400c / kg and of reasonable density (much higher than PLA, not quite as dense as lead, but im ok with staying nontoxic)
The cheapest wheel weights I could find were 19c / oz
The cheapest washers I could find were 22c / oz
The cheapest non-lead BBs I could find were 21c / oz
I don’t quite like nuts or bolts form factor (for stuffing) but I could only find 20c / oz
Sand works, but can just be a bit messy. I’ll bet you can also go to a local wheel shop and ask them if they’ll give you some used wheel weights - I went to mine for another project and they happily gave me a whole 5gal bucket full of them. They’re typically just steel so almost worthless in scrap weight. Just ask nicely!
I’ve been working on this issue for the better part of a year to find an optimal solution. There are none, each solution, whether it be sand, steel blanks, ball bearings or pennies, all have advantages and disadvantages.
TL;DR: Pennies are the most cost effective solution on the basis of weight and volume.
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Little-known fact: Pennies (both Euro and USD) are actually copper-clad aluminum. They weigh approximately 30% less by volume than steel. However, on a cost-per-volume basis, pennies are cheaper than purchasing aluminum blanks of the same size. It may seem contradictory, but the metal’s value is higher than the currency’s face value. So why aren’t people melting down pennies for the aluminum? The answer: The energy required to melt the metal exceeds the combined value of the metal and the cost of electricity or a gas furnace.
You might consider different sized ball bearing balls which you can buy off Amazon and probably Aliepress. I needed small bearing balls for a project and because I was unsure which size would work best I bought various sizes, some of which were quite tiny.
A side note but copper is toxic. Not as toxic as lead but it is. Also used in pesticides.
This, coming from a community that happily sniffs molten plastic fumes…
I have a feeling the Chicken Little brigade that declared copper toxic didn’t get the memo that they have zero credibility. Why? Because if copper were truly as hazardous as they claim, you just know the EU would have banned coins overnight, labeled the material a biohazard, and waged war on every electronics company on the planet. Funny, I must have missed that breaking news segment.
But don’t worry—if the tree huggers had their way, they’d wipe out 80% of humanity for being enemies of Gaia, force the survivors to live off the land, dig under rocks for grubs, and die of staph infections since life-saving technology is inherently evil. Fortunately, no one takes them too seriously.
This would probably be the same brigade that declared lead pipes topic, moved to copper… oh no, copper, is toxic… PVC… oh, nuts, that’s toxic also! What do we do now? Maybe it is the cynic in me, but it seems might convenient each of these “concerns” were raised once the market had reached saturation… time for a new model?
There was the minor detail that lead pipes were only “toxic” if you kept messing with them… once they formed a skin they were perfectly safe. Anything in the right circumstances is toxic… i.e. see how you feel after having stuck your head in a bucket of water for 10 minutes… or being stuck in a 1000psi oxygen rich environment for 10 minutes… somehow I don’t think you’ll have anything to say about it.
Rather than just sticking heads in the sand, we should be evaluating the risks of the materials on a case by case basis, and using the best material for the job. i.e. a lead sinker entirely encased in a plastic print… who exactly is that going to harm? If you are concerned with handling it, wear gloves.
Thanks for the replies. Pennies it is, I guess. I like the idea of used wheel weights but it would need cleaning, and I am terminally lazy My bank’s gonna be really confused as to why this guy wants 100 pounds— err, 100 dollars worth of pennies.
The sand thing is hilarious Some things seem like such a good idea till you try it. I have been guilty of the “pause print, drop magnets in” just to have them ripped out by the ferrous extruder passing by. That’s the story of why i have the bottle of ultraquick-dry superglue next to the printer…
As far as copper clad currency being toxic as compared to lead shot, I award you +100 pedantry points, and the Gold Star of Whoosh
Fortunately, no one takes them too seriously. 
Maybe it is the cynic in me, but it seems might convenient each of these “concerns” were raised once the market had reached saturation… time for a new model?
My bank’s gonna be really confused as to why this guy wants 100 pounds— err, 100 dollars worth of pennies.