Create a void in the middle of a solid?


#1

Hey guys, first post here. Me and my partner are trying to embed NFC chips in tokens that we are 3D printing. Basically what we want is a token that is 40mm in diameter to have a square void in the middle of it of 20mm to embed this chip. When we model this with Rhino we are not able to boolean them or join them because of the void. Is there anything to remedy this??


(Willem Derks) #2

Hi Tyler,

This might be a solution:

HTH
-Willem


#3

Thank you! I will try this when I get home.


#4

Just curious, how do you 3D print the object with the chip inside?

–Mitch


#5

The other thing we used to do in the old days was to join the inner and outer surfaces with a tiny tube. Depending on what 3d printing technology you’re using (I presume FDM since its the only one I can think of where you could embed the chip by pausing the printer halfway through the print) this tube could end up being filled in anyway, if its really tiny.

-Gavin


(Kyle Houchens) #6

+1 on tiny tube connecting the inner void to the outer surface- very easy to see if it’s right And easy to fix if it’s not.

  • k

(Willem Derks) #7

Noteworthy I guess:
The tiny shaft be best placed in the horizontal (printing) plane, thus appearing only in one slice (if at all)

-Willem


#8

I’m guessing if you would make the tube 1 micrometer, or even smaller, it would not be noticeable on the printing? Or would the software for printing actually prioritize the fact there should be á hole no matter how small, and create an opening at the minimum size it can?


#9

Depends what software you’re using for printing. I have an Ultimaker and use Cura. It doesn’t treat tiny features any different from large ones. I actually have to draw vertical holes 0.3mm larger than I want them because internal radii come out too small, even though the external dimensions of objects come out the right size. Cura would create solid walls around the tube, though, whereas the rest of the internal void would be an infill pattern, and you would notice a dimple on the outer surface, even though the hole would be totally sealed up.


#10

So I thought I’d try what you’re doing, and you don’t need a tiny tube.

I just draw a sphere in rhino, then a cube inside it. Exported that as stl, and opened in Cura (my 3d printing slicer).

Here’s a screenshot showing the print halfway through, and you can see it has recognised the cube in the middle as an internal void.


#11

So the 3d print software just counts an object in an object as empty space? That seems like a nice approach of the Cura guys.


#12

3D printing software doesn’t know anything about surfaces or volumes. All it knows about is slices of the STL, which are polylines. The way it determines if there is a hole in the part is by nesting (a lot like Rhino does when creating planar surfaces from nested closed curves). So if a second loop is found inside the first, that is a hole. If there is a third loop inside the second loop, that will be part material again, etc…

My 3D printer software does the same thing, but since it also prints support material, depending on the geometric config of the part, it will fill the hole with support material. You can go in and edit that out, but it’s a bit of a PITA. If you have something like a powder printer, powder will also get stuck inside, and that you can’t edit out…

–Mitch


#13

curious about this too… anybody?


#14

@Helvetosaur: In Cura you can turn support material off. Actually you can see in my screenshot that the option is unticked.

@jeff_hammond: The way I would do it on my Ultimaker is like you see in the above screenshot - the printer prints layer by layer. When it is halfway through, I would pause the print, drop the chip inside, and then resume printing.

It actually does a reasonable job of closing up the internal void, because the plastic gets stretched across inner walls of the void to form a roof over it, and it tends to stick to the walls. It does droop a bit on the first layers, depending on the temperature you print at, but for an object like this it wouldn’t matter, unless the chip would be damaged if hot plastic touched it. Otherwise you could design the internal void with a pitched roof with angle about 45 degrees and then there would be no drooping.


#15

neat. thanks.
I’ve never seen something being printed 3D so I don’t know if/when you can pause it or stick your hand in there etc.