Step 2: Opening Up the Ping-pong Balls

A 2 to 2.5 cm hole is made in each ping-pong ball.  The inside diameter of a standard office tape roll is just the right diameter to mark it out.

Drill a hole well inside the marked circle, as a starting point for cutting out the marked area with curved scissors. Cut it out slightly small, to finish it with sanding paper: first put it on flat sanding paper on your work surface and sand by rotating it. Do this till the outside of the edge is smooth. Then make a roll out of the sanding paper and put it in the hole.  Smoothen the inside of the edge by rotating the roll.

This usually takes only a couple of minutes, as the material the pin-pong balls are made out of is quite soft. The resulting diameter of the hole is not critical. It can deviate a couple of mm.
<p>Thanks! Great project - made it with acrylic glass and cyan leds.</p>
Can you suggest anything else to make the toms and legs out of?
You can use any stiff, non ferromagnetic material, thick card, plastic, aluminium. For me, plywood is the easiest.<br>But is your problem with the plywood or rather the laser cutting?<br>You can use a fret saw to cut the plywood by hand. It takes time and effort, but I made prototypes that way.
<p>I like it!</p><p>thanks!</p>
thanks,good idea
You should try to sell DIY kits on Etsy, I know I would buy one
Thanks, but they would turn out a bit expensive, I'm afraid.<br>I'm stil looking for ways to make them cheaper and less labour intensive.<br>I made a version with little work up to the point were I can present them as a kit:<br>https://www.instructables.com/id/Spreading-Love-with-Robots/<br>But these cost about 45 EUR in materials and laser cutting for one pair.<br><br>But I will come back to you when I have newer versions.
this is a awesome project for someone you love. Anyway you can post a scan print out of the wooden arms, legs, and body? it's hard to judge distant from the hole to match up with the nuts and ping pong ball to make it fit without print out.
Thanks, <br> <br>There is a design in svg format attachred to step 1. <br>Svg can be opened in a browser or with freeware like Inkscape. <br>The design in the svg makes the robots slightly taller than the version in the pictures. <br>Do you need anything more? Putting the parts on the printer is not practical, as this would mean asking the robots back to dismantle them. <br> <br>Good Luck!
Nice project
Oh so creative!
SUPER!!! Are you working on a version that kids can make?
Thanks!<br> <br> From step 8 on, kids should be able to build it themselves, with some help for the younger ones.<br> <br> I am thinking of simplyfying things for the complete build. My main challenge is an alternative sollution for the switch. I have a couple of ideas to test.<br> <br> I'm also thinking of dropping the ping-pong balls alltogether and work with a completely acrylic assembly.<br> <br> For kids, a solder free sollution would be very welcome too.<br> <br> For myself I'm thinking of using a template to help drawing the faces, but for&nbsp;kids that is not the way&nbsp;I would go. On the contrary, they should be free to decorate as they wish.<br> <br> I'm also thinking of rechargeable version. A solar cell could work, but I would rather add a third function to the magnet: next to the kissing, the switching, I would also like to use it in a &quot;generator&quot; as in a &quot;shaker flashlight&quot;.
so lovely, thanks<br>
So cute and well documented. I love the way they clack when they kiss. :P

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