# My Scouting Family (of 3D printed Boy Scouts)!



## calinb (Apr 4, 2015)

I'm happy with my 3D CAD model and print settings. Adding the internal stiffener really stiffened up the slingshot. Like molded injection parts, most plastics cannot be printed completely solid without major shrinkage problems when cooling. These prints have a honeycomb cores.

I'm printing in nylon, which is a fairly difficult material to print, but it's one of the strongest materials for hobby printers and it doesn't usually fail catastrophically when it does reach its yield point, like the more brittle plastics used in 3D printers. Instead, it bends. 3D printed nylon parts also require a lot of hand cleanup work, because nylon leaves blobs and strings when the printing nozzle jumps (even with optimum printer settings) and extra material designed into the print to help it stick to the printer bed (a "brim") must be cut and sanded away from the part's contact point with the printer. So there's a lot of hand work with an Xacto knife and Dremel tool after printing a slingshot in nylon--maybe 20 to 30 minutes of effort, even, depending on one's aesthetic pickiness!

I think the new stronger and less brittle PLA 3D printing plastics will work well for slingshots and hardly require any hand cleanup at all. They are much easier to print, but also much more expensive than the nylon trimmer line I used here. The Boy Scout uses about $1.80 in nylon trimmer line. It would cost about $4.10 using one of the newfangled PLA plastic filaments, but it would be almost ready to go right off the printer and look prettier than nylon too. Nylon does not produce as nice of a finish as PLA or ABS.

The Boy Scout was a bit large for my 9-year old daughter, so I scaled it down to 80% and installed very light Gold's Gym purple bands (0.011" thick). My daughter loves the color and she can easily pull to her cheek. I'm calling her slingshot the Brownie Scout.

Then I stretched the grip area to 110% but used the same width and lengths forks and printed a 1" thick version for myself. (My printed Boy Scout is 3/4" thick). Bill already has an Eagle Scout so I call it the "Big Scout." I like the little extra space between my fingers, but I might have to try its stretched grip in combination with the 3/4" thickness of the Boy Scout (a "Scout Master" ? ). 1" is pretty thick! That's the cool think about 3D printing, once you have a good 3D model, you can easily tweak to your heat's content!

Here are all three slingshots. I am finishing up the last of extra copies of all three of them to send to Bill Hays for his evaluation or whatever he wants to do with them. I'm interested in starting a "Print One For A Kid" campaign!

-Cal

P.S. The Boy Scout on the right in the photo doesn't have the internal stiffener (it was the first one I printed). You can just make out the stiffener through the translucent plastic (it's sort of a horse shoe shape) below the "U" of the forks in the Big Scout on the left. The newer version also have a slightly denser honeycomb pattern than my first one. (But get it too dense, and the part will warp on the printer as it grows and cools.)


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## calinb (Apr 4, 2015)

I don't know how I ended up with a duplicate thread (but without the photo above) here: http://slingshotforum.com/topic/42457-my-scouting-family-of-3d-printed-boy-scouts/

I can't even edit it (to mark it obsolete), though I was allowed to edit this one. Maybe a mod can delete it so people will reply the THIS thread and not the one without the photo.

Thanks,

-Cal


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## e~shot (Jun 3, 2010)

Looks cool!


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## bigron (Nov 29, 2012)

they turned out great,congrats


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## GHT (Jan 22, 2013)

interesting project, nice one.


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## calinb (Apr 4, 2015)

e-shot, bigron, GHT,

Thanks for your encouragement! Here are my two latest slingshot prints. I printed them in Taulman 618 (a commercial 3D printing nylon filament) and the plastic turned out stiffer than my trimmer line prints , but the stiffer plastic is more a function of how I dry the filament before printing with it than anything else. Nylon picks up water from the atmosphere like crazy.

I stretched the 3/4" thick Boy Scout in the grip area by 10% and it fits my hand great! I call it the "Scout Master." I'm shooting it better than any slingshot I own, having taken a long hiatus from slingshots between my childhood and current middle age.  I'm able to hit a soda pop can most of the time from 10 yards now and hope to be able to hit those pop cans just about every time someday (and maybe those plastic whiffle golf balls too). Then I'll be ready to hunt!

Here's the result of the latest result with the latest in slingshot fabrication technology propped up against a future project in the oldest fabrication technology (a fork from a wild plum tree I cut down in my yard).

Given the availability of the Rambo .stl file for printing, I decided to print one of those too. First, I needed to split the model and add holes and counterbores for plastite screws, because it has too much overhang for printing in nylon (and it really should be split for even the less demanding PLA printing media). Here are several photos, showing where I put the screws. If I ever make another one, I think it would be easier to cut the mesh model right at the front face of the forks instead of bisecting the forks. The Rambo palm swell is a bit too large for my hand, but I think it turned out quite well.

I got the print time for a Boy Scout down to about 5-1/2 hours. The Rambo takes twice that long to print! Of course there's still another half hour or so in cutting and sanding blobs off the printed part, as always with anything complex (requiring "jumps" by the print head nozzle) printed with nylon. You can see the matte effects of sanding. I plan to try bead blasting the parts after removing the blobs to see if it yields a more aesthetic surface. When printed correctly, PLA and ABS 3D prints have little or no blobbing problem, and these plastics produce a nicer surface with greater resolution than nylon. I mostly print structural parts and prototypes that must be strong and that's why I like nylon. Plus, nylon trimmer line is cheap (~ 10 USD / pound). PLA and ABS also print much faster than nylon (PLA about 4 times faster on my Ultimaker 3D printer).


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