Train Mold (2 part) for recycling crayons

thingiverse

A fun way to recycle those old and broken crayons you've got stuffed in some bin. Each train needs a bit less than 1.4 inches of crayon (standard diameter) - not counting what stays in the melting pot or cup. Prep: Print both halves (STLs are provided for each, right and left) (flip over the STL that is upside down) Wrap the two halves together tightly with a rubber band - because of the mirror image on each piece, and the interlocking features, the orientation should be pretty obvious. you can also use a clamp to hold the two halves together, but a rubber band is more convenient, especially if you want to chill briefly in the fridge/freezer. Method I used for melting the crayons: 2 plastic cups (kid cups from most restaurants) Fill one cup about 1/4 full with water Places the broken pieces (smaller pieces melt faster) in the other cup and place on top of the water to float in the other cup. Place in the microwave and run for 30 seconds (check and repeat until there are no lumps). Taking the top cup with the melted crayon out of the bottom cup (careful of steam), pour into the funnel shape on top of the mold. If properly melted, you should be able to pour a small, steady stream directly into the hole. Stop when the funnel begins filling without draining. A spot of color should be visible in the vent hole if the pour went well. After letting it cool and harden, remove the rubber band and separate the two halves. Gently press upward on the bottom of the train until it starts to move, then press lightly on the roof of the train to finish breaking it free. Other comments: You may want to use a cooking oil or spray to lightly coat the surfaces as a mold release. I used a cotton swab with mixed results. If a train breaks in the mold, a wooden tooth pick can work to remove the pieces and you can try again. Green crayons did not work well for me - very clumpy