My son is a voracious crayon user. unfortunately he likes to put the maximum pressure to get the darkest colors and we end up with a lot of broken crayons. I designed this for two reasons, one to support the crayon the way he colors, and two to hold the broken crayons so they are not wasted.
Another benefit would be small hands, as the size is a bit bigger than of a Ticonderoga Tri-write pencil and you can use the smaller less expensive crayons compared to the larger triangular ones.
I have added version 3 of the design. My son asked for a more controlled way to push the crayon fragment out. Using the screw library in MCAD, I added an auger 'thread" to the pusher and subtracted the same from the holder body.
It's best if you have the knurl surface library (http://www.thingiverse.com/thing:32122) in your MCAD library folder as this is used to provide some bit at the tip of the holder.
I printed at 0.2mm, 30% fill, and 1.2mm wall thickness and it's very strong.
The pusher it in case the crayon slips in too far, but a pencil will work just as good.
The auger is if you want more control over the amount of "push" you give to the crayon fragment.
Use: Just slide the crayon in and add a small rubber band to hold it tight. (I planned for an o-ring but can find the one I had in mind so I'll check the hardware store next time I'm in there.) You can roll the rubber band down to remove/replace the crayon too.