Needing more than a spark test?

WobblyHand said:
Here's something interesting, but not sure it is cost effective. Prusa has introduced 3d printing filament that is 75% by weight tungsten. It is designed for shielding radiation without having to use lead. It's printable. Here's a link to the Prusa blog announcing it. https://blog.prusa3d.com/were-launc...ungsten-75-for-radiation-shielding-use_75919/ It costs $229/1kg spool.

By the way, @graham-xrf how did your lead machining go?
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Sold by the kg, eh? Tungsten's density is very high @ 19.28 g/cm^3 so that doesn't come to a whole lot of filament. 1 kilo of 100% tungsten would be a bit less than 52 cubic centimeters. If the remaining 25% of that filament weighed nothing, you'd get about 70cc's worth of filament. I think we're stuck with lead :).
 
homebrewed said:
Sold by the kg, eh? Tungsten's density is very high @ 19.28 g/cm^3 so that doesn't come to a whole lot of filament. 1 kilo of 100% tungsten would be a bit less than 52 cubic centimeters. If the remaining 25% of that filament weighed nothing, you'd get about 70cc's worth of filament. I think we're stuck with lead :).
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It's not as small a length as you think, although I still think it isn't cost effective.

The claimed density of the filament is 4 gm/cc. The diameter is 1.75mm, or 0.175cm. A volume of 1cc would be 41.575 cm long and weigh 4 gm. (length = vol/(pi * (d/2)**2) = 1cm3/(pi * (0.175/2)**2) = 41.575cm). So 1 kg would be 250x longer. Therefore the filament length would be 41.575 cm x 250 = 10393.79 cm = about 104 m.

When printing, the slicer can determine the cost of the object by knowing the spool cost and the amount of filament extruded. Oh, one needs to print using a hardened steel nozzle as the tungsten is too abrasive for a standard brass nozzle. And to do much good at suppressing radiation, one would need to print at 100% infill, in the critical areas, which would use up filament. There are other metal filled filaments around, but I thought this tungsten filled filament was moderately interesting.
 
WobblyHand said:
It's not as small a length as you think, although I still think it isn't cost effective.

The claimed density of the filament is 4 gm/cc. The diameter is 1.75mm, or 0.175cm. A volume of 1cc would be 41.575 cm long and weigh 4 gm. (length = vol/(pi * (d/2)**2) = 1cm3/(pi * (0.175/2)**2) = 41.575cm). So 1 kg would be 250x longer. Therefore the filament length would be 41.575 cm x 250 = 10393.79 cm = about 104 m.

When printing, the slicer can determine the cost of the object by knowing the spool cost and the amount of filament extruded. Oh, one needs to print using a hardened steel nozzle as the tungsten is too abrasive for a standard brass nozzle. And to do much good at suppressing radiation, one would need to print at 100% infill, in the critical areas, which would use up filament. There are other metal filled filaments around, but I thought this tungsten filled filament was moderately interesting.
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If the filament is claimed to be 75% tungsten and W's density is almost 20g/cc I find the 4g/cc spec for the filament to be at odds with the percentage claim. Something doesn't pencil out, don't you agree?

Not that it really matters. I think lead is much more cost effective, given the relatively simple shield geometry we need.
 
homebrewed said:
If the filament is claimed to be 75% tungsten and W's density is almost 20g/cc I find the 4g/cc spec for the filament to be at odds with the percentage claim. Something doesn't pencil out, don't you agree?
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It's claimed to be 75% tungsten by weight, not by volume. I haven't worked that out all the way through to density. On the surface it sounds like marketing is at work... FYI, PETG density is 1.27 g/cc.

250 gm PETG is 196.85 cc ( 250 gm / 1.27 gm/cc )
750 gm W is 38.9 cc ( 750 gm / 19.28 gm/cc )

1000 gm / ( 196.85 + 38.9 ) = 4.24 gm/cc so the claim is about right, if I did my math correctly. Given that the tungsten isn't solid, but in fine powder, that isn't so far off at all.

Using the filament density and cost, for the 8 source ring I printed a while back, printing in tungsten filament would use 7.86m of filament, cost $17.31, and print in a couple of hours. This is will 100% infill. That isn't that terrible... No the shielding wouldn't be as good, but for a tricky section that would be hard to fabricate, it is an interesting option.
 
I didn't catch the "by weight" part, it all makes sense now. I _had_ wondered how the heck a 3D printer would deal with filament that had 75% tungsten in it....
 
Having tagged a long a bit, I will admit to getting sort of intrigued. It sounds like both Graham and Bruce are working on board designs. If one of you gets to the point of actually getting PCB's made and wants someone to pick up cost of a board run, I'd be willing to do so to get a couple of blank PCBs. I realize this is still working at the proof-of-concept level so I'm not asking for a guaranteed design!! Maybe even some collaboration if it makes sense on the layout work. Just need to be careful not to get in anyone's critical path as I'm in for some significant medical downtime.
 
homebrewed said:
I didn't catch the "by weight" part, it all makes sense now. I _had_ wondered how the heck a 3D printer would deal with filament that had 75% tungsten in it....
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It turns out, one can buy 100gm of this filament, as opposed to having to buy a full spool. That's an outlay of $24 plus whatever shipping. It would only make a single part, but that's a lot better than having to pony up $229 or whatever, for a crazy idea. Would still have to buy a hardened nozzle but they are pretty cheap.
 
rabler said:
Having tagged a long a bit, I will admit to getting sort of intrigued. It sounds like both Graham and Bruce are working on board designs. If one of you gets to the point of actually getting PCB's made and wants someone to pick up cost of a board run, I'd be willing to do so to get a couple of blank PCBs. I realize this is still working at the proof-of-concept level so I'm not asking for a guaranteed design!! Maybe even some collaboration if it makes sense on the layout work. Just need to be careful not to get in anyone's critical path as I'm in for some significant medical downtime.
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Can't speak for Graham, but I've not been working on mine for a while. Got way laid doing other stuff, like installing a set of glass scales on my lathe. The scales have taken a lot more time than I thought they would.

Need to get back to the layout. I struggle with doing the power planes, aka zones, and ground plane planning. I'll figure it out - but it takes a clear head to do it. If I get to the point of releasing a design, and I hope I do sometime this spring, I can order a few more boards.
 
WobblyHand said:
Here's something interesting, but not sure it is cost effective. Prusa has introduced 3d printing filament that is 75% by weight tungsten. It is designed for shielding radiation without having to use lead. It's printable. Here's a link to the Prusa blog announcing it. https://blog.prusa3d.com/were-launc...ungsten-75-for-radiation-shielding-use_75919/ It costs $229/1kg spool.

By the way, @graham-xrf how did your lead machining go?
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Not yet! It is on my desk, glaring at me! I have lately been back into woodworky stuff, and building construction related stuff, and getting my Kicad circuit to the point I can try for the PCB. For sure, the lead machining is going to be "interesting" to say the least. When I have something that is not an unholy mess, I will post pictures on the XRF thread. Now that I have seen Mark has made actual spectra-looking plots, I definitely want to find out whether we really can make displays of "what's in there" with a home project that does not cost the Earth. :)
 
rabler said:
Having tagged a long a bit, I will admit to getting sort of intrigued. It sounds like both Graham and Bruce are working on board designs. If one of you gets to the point of actually getting PCB's made and wants someone to pick up cost of a board run, I'd be willing to do so to get a couple of blank PCBs. I realize this is still working at the proof-of-concept level so I'm not asking for a guaranteed design!! Maybe even some collaboration if it makes sense on the layout work. Just need to be careful not to get in anyone's critical path as I'm in for some significant medical downtime.
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I am fully aware of the trials you face, and we will fully understand when you can be away fighting other battles. You have the Kicad experience, and your comments and contributions have already helped us up the learning curve. When I have a draft layout made, I will, of course, post it, and discuss. When I have some actual PCBs, I am OK will send you one gratis. We can arrange the details by PM at the time.
 
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