Machining wax
I was beset with making a concrete grave marker for a beloved pet and decided to use machining wax to start the process. I hadn't used it before so didn't know what to expect.
Here's the product: https://www.machinablewax.com (blue bulk wax)
I bought the pellets thinking it would be better to be able to cast my own. Wax takes a lot of heat to melt and shrinks about 5% so it was a bit of a chore to cast the 12x8x.75" block I needed. It came out great though.
I could have made a negative directly using my SB but the tool marks would be everywhere and the quality would be reduced. Instead, I opted to make a positive from the wax and cast a negative for the mold using epoxy.
To machine the wax, I used a regular 60 degree V tool at 6k RPM's and 6 IPS. The key to carving wax is speed and slow RPM's. It's a soft material with a low melting point so ejection of chips is extremely important for good surface quality.
Running the program the first time left a lot of "fuzzies" in the letters so I ran it a second time and then finally, a third time with the spindle off. That cleared the fuzzies and left a very nice finish.
Oddly, machining wax can be wet sanded easily so I cleaned up the surface of the wax using 320 and then 600 and it was very smooth.
Next, I set up the wax for the epoxy negative casting. That went very well and used only about 75mm of epoxy.
The result was a very tough and very close to perfect casting. I used the epoxy negative as the bottom of a mold, poured colored concrete into the mold and it turned out quite nice.
To sum it up: Using machining wax to build molds is technically possible but it is time consuming. Starting with precast blocks would have saved a lot of time and effort vs. casting my own. Being able to sand the wax turned out to be the biggest surprise and made the finished product nearly perfect. I had one scratch in the wax that I had to deal with post cast with epoxy but the scratch was in the wax so it was a easy to simply sand out the scratch in the epoxy.
I would post pictures but it's a rather sad piece so I'll just use words.
ShopBot Details:
2013 PRS 96x60x12 (Centroid upgrade)
4hp Spindle
12" indexer
Aspire
Rhino
Fusion 360
Ferrari 360
Prusa MK3S+
Prusa XL multi-tool