Crayon Maker/Recycler Kit with Sharpener (Parametric)

This is a fully parametric kit that will allow you to make triangular crayons (or recycle bits and pieces of old crayons into triangular crayons) and a sharpener. This shape is easier to cast, easy for little fingers to grasp, and easier to stack. It also won't roll off the drawing surface, and promotes a proper pencil grip.

Many aspects of the kit are parametric, such as number of crayons, thickness, length, sharpening angle, etc. You may need to tweak the settings a bit for the best results on your printer.

There's an STL for each part using the default settings. You can make just the crayon mold, or both the mold and a sharpener that fits the crayons you specified. Follow the instructions and take a look at the pictures for details.

This is a great project to do with kids -- I've tested it! :)

There are 21 parameters, and the code is fully commented, so tweaking it should be straightforward.

Check out the photos (in order) to see the crayon-making process.

CRAYONS:
1) Choose some values in the "User-defined values" section, render, and print. Make note of the volume of plaster that will be required for the mold. (It will be echoed out below the rendering in OpenSCAD -- about a half cup for the STL.)

2) Place the mold onto a flat, nonporous surface (like glass) and coat the exposed surfaces with a thin layer of Vaseline, dish soap, or liquid bees wax to act as a release agent. (Photo 01)

3) Mix some Plaster of Paris (Photo 02), and pour over the printed positive mold to the top. Carefully vibrate the surface to help settle the plaster and release any bubbles. You can often do this by simply "drumming" around it with your hands. Level the top (Photo 03), and allow the plaster to dry completely.

4) Once dry, cut the sprues at the bottom against at the wall. This will leave the wall on outside of the negative mold, which can protect it a bit. Then remove the printed positive mold from the plaster (Photo 04), and coat the inside with dish soap to act as a release agent. (Photo 05)

5) Use a metal cup and a pair of vice grips to carefully and slowly melt broken pieces of crayon with a torch or stove burner (Photos 06 and 07), and pour the melted wax into the crayon molds (Photo 08). You can also put various sizes and shapes of crayon pieces into the mold and pour over them to join them together with some melted crayons.

SHARPENER:
6) Print the Sharpener Guide (sharpenerGuide()) and Cutter (cutter()) parts, which are sized to fit the crayons you made. Be sure you use at least a couple of perimeters on the cutter, because you're going to sand it down in the next step to sharpen it.

7) Using a file or sandpaper, clean up the sharpening edge and file or sand down the angled flat surface until the cutting surface is sharp.

8) Snap the guide into position, insert crayon, and carefully turn to sharpen. If it's too tight with the dedents, just flip it around and try it the other way. You can add a little bit of crayon wax as a lubricant if necessary to make it easier to turn.

TOOL CHAIN AND PRINT SETTINGS:
For this I used slic3r 0.9.1, Marlin, and j-head 0.5mm with cheap 3mm "repraper" PLA filament (from China). I print onto glass covered with window tint with a thin coat of ABS juice. The printbed is heated to 90 for the first layer (measures about 80 with the IR thermometer), and 75 for additional layers. I used two perimeters, 15% honeycomb infill, and 0.33mm layer height. Hot end temperature depends on color, but is usually around 185.