A major issue that I ran into when I first started working with my new CNC machine was the cost of raw materials to machine. Sure, a block of plastic is not terribly expensive by itself – but figure in the cost after you mess something up and the cost becomes quite unreasonable. For this reason, I began looking into machinable wax.
Machinable wax is a very hard wax that won’t gum up a cutting tool, is soft enough to machine quickly and most importantly is completely reusable! Since I am cheap, I decided to make my own, which is actually quite simple and could be considered environmentally friendly since we use recycled plastic bags. Be aware that this Instructable is DANGEROUS! We will be melting wax
around 300* and this wax will be thick and sticky so it will literally burn your skin off faster than you can say “OUCH!”
(The basic recipe is 4 parts wax to 1 part plastic)
You will need:
- Paraffin Wax (Available at Hobby Lobby)
- Plastic Shopping Bags (HDPE or LDPE, Recycle symbol #2 or #4)
- Deep fryer WITH adjustable thermostat
- Candy Thermometer (to make sure your fryer thermostat is working correctly)
- Wood Spoon
- Leather Gloves
- Safety Glasses
- Molds (I’ve used Tins, Wood frames, and Cardboard)
- Wax paper is handy
- A scale to measure wax/plastic
Step 1: Melting Wax
Paraffin ignites at around 400*F.
Don't forget that what your looking at is melted wax, not water. Hot water will splash and drip off of you, hot wax will splash and STICK TO YOUR SKIN! So be careful....
Step 2: Melting Bags
Once you hit 300*, begin adding the plastic bags, one at a time. It helps to cut them into strips so that they wont ball up, but I don’t have any data to support a specific way just yet. The more your stir this mixture, the faster the bags will dissolve (Just don't get too crazy, you could introduce a lot of air into the wax). Continue adding bags until they won’t dissolve any more. Most of the plastic should have dissolved, leaving just a few chunks left. With LDPE this is usually a 25% mixture, whereas HDPE bags are around 15%. Stay patient, this process can take a while.
Step 3: Casting the Wax
If you chose option #2, turn your fryer back on and make sure your wax is liquid before pouring. When pouring into molds, pour slowly but be committed as you do not want wax to drip down the side of your fryer. Once poured, cover the molds with a towel so that they cool slowly. The slower they cool, the more likely that air bubbles will escape before getting stuck in the wax.
Step 4: Machine That Wax!
Recycle Your Wax
When recycling your wax, I recommend using no more than 50%-75% reground wax. This is due to the fact that plastics degrade rapidly when heated (think compost) and can start to smoke/burn/ignite if you are not careful. Therefore, start by melting paraffin wax, adding new bags and THEN adding your recycled wax.
Good luck and be safe!