This is a toy for infants. My son was playing with it, and I started wondering how you could manufacture this. I can't think of any reasonably cheap way it could be done.

spherical toy

I believe it's made of plastic and not silicone. It's flexible, but not elastic.

My first thought would be injection molding, but I can't see any way to get parts of the mold in and out of the sphere. My wife suggested that perhaps the mold had no interior surface and was rotated like they do with chocolate, but I don't think that's the case, because if you look carefully you'll see that the inside surface is rounded and not flat.

Anyway I'm stumped. How do you think they did it?

  • $\begingroup$ Have you heard of blow molding? Or rotational molding like your wife said. $\endgroup$
    – DKNguyen
    Commented Aug 22, 2021 at 2:24
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    $\begingroup$ it's baked on a cookie sheet in the 4th dimension ... lol $\endgroup$
    – jsotola
    Commented Aug 22, 2021 at 7:03
  • $\begingroup$ Injection molded; That is why model makers or mold designers are well paid. There are "side action" and other tricky stuff in the die. $\endgroup$ Commented Aug 22, 2021 at 15:12
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    $\begingroup$ can you see any gate marks, ejector marks, or parting lines? $\endgroup$
    – Pete W
    Commented Aug 22, 2021 at 16:06
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    $\begingroup$ To supplement the answer by @StainlessSteelRat, the infant version of this toy that you have is covered in an extra layer to conceal any possible sharp edges from the plastic welding process. It has basically been dunked in the equivalent of Plasti-Dip. We had one. If you pop out the three rattles, under one of them, you will see the trim mark from where they held it to tank dip it. At least on ours anyway. $\endgroup$
    – Stewbob
    Commented Aug 23, 2021 at 20:18

2 Answers 2


OP injection molding tag is correct. OBall uses injection molding and plastic welding.

The OBall is the invention of David E. Silverglate.

Toy Ball Apparatus with Reduced Part Count


Reduced image from Kids II.

It consists of four identical, flat, injection molded, pentagon and hexagon shapes with circular (or elipitical) holes, which are shaped and plastically welded into spheres.

Pentagon and hexagon edges are the same size and individual connected circles are only connected along one edge. The four shapes are clearly shown in colors above and from the patent. Solid lines on each part are hard connections, while dashed lines represent connections within the part. Patent shows how individual edges on parts are interconnected. Injection molding with a plastic (PETE [or PET] from Jim Clark link: What is Oball made of?) at a higher melting material and welded with a plastic at a lower melting material.

Figure 8 from the patent. enter image description here

[0022] The shape and number of the mesh components 14 are designed in a manner that decreases manufacturing costs incurred using a process such as injection molding. Regarding the number of mesh components 14, it will be appreciated that when four mesh components 14 are utilized the production time may be significantly reduced when compared to a toy ball apparatus 10 having ten mesh components. The decreased production time may in turn decrease the toy ball apparatus's manufacturing cost.

[0029] FIG. 9 illustrates toy ball apparatus 10 in its assembled State, in which the plurality of mesh components 14a, 14b, 14c, and 14d have been coupled to enclose the closed Volume 20 and form the mesh 12, by joining adjacent mesh components 14 along their cooperative mating Surfaces 19 and securing the mesh components 14 together, for example, by plastically welding the mesh components 14 together along the cooperative mating Surfaces 19.

Each part has 3 pentagons and 5 hexagons.

Clearly Part B and C are the same. But A and D are obfuscated by the patent lawyers. Edge numbering indicates they knew all parts were the same. They just divided it to obscure the true inovation.

In all 4 parts, central hexagon has no writing on it. It is surrounded by 3 pentagons and 3 hexagons. The final hexagon with A1,A2,A3&A4 (or B1,B2,B3&B4, etc.) connections are always connected to hexagon with A16&A17 (or B16&B17, etc.) connections.

So tooling is for one part, which means true inovation was making ball from 4 identical flat injection molded parts.

SolidWorks drawing of ball made from 4 identical parts.

enter image description here

  • 3
    $\begingroup$ How many millions of those do you think they planned to make to justify the work that went into developing the manufacturing process? Heh. $\endgroup$
    – DKNguyen
    Commented Aug 22, 2021 at 18:40
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    $\begingroup$ @dknguyen Well there are multiple toys with same process. Possible reuse of molds. But yeah the marketing is more impressive than the engineering. $\endgroup$ Commented Aug 22, 2021 at 21:29
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    $\begingroup$ Note that the shape with the hexagons and pentagons is exactly the same as the one on a typical soccer ball. This mathematical structure was already known in antiquity. So the plastic welding is the innovative part here, the complicated picture with the instructions which part goes where is not. $\endgroup$
    – quarague
    Commented Aug 23, 2021 at 7:33
  • $\begingroup$ It's just surprising complex construction for a childrens toy. I think if someone pitched me that, I would be like "redesign it so that it can be injection molded in one step, kids won't notice the difference". $\endgroup$
    – Drew
    Commented Aug 25, 2021 at 23:40

One way of making it is to flatten an Icosahedron on a plastic sheet As the figure and after molding while it is still malleable bend it to shape.


Flattenned Icosahedron

  • 1
    $\begingroup$ This answer would benefit from more explanation on the meaning of "bend it to shape"; in particular, how to go from the 20-sided icosahedron that you show, to the 32-sided truncated icosahedron, the same shape as a (soccer) football. $\endgroup$
    – Stef
    Commented Aug 23, 2021 at 10:13

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