a rapid ring – part 3

Melissa reveals – a rapid prototyping process – courtesy of the good folks at RMIT who have this new whiz-bang machinery.

Building this ring was left up to the machine at RMIT, which relied on a Rhino STL file for its instruction. In the actual process of laying down the model in such a state that once done it will be ready to be cast, it has two type of wax at its disposal.

The purple wax is for building supports for any overhanging parts of the design. For example, each of my quatrefoil-shaped windows would have had to been filled with the purple build wax in order for the blue wax to have something to build on top of as each hole curved back up.

Each layer of wax is added to the previous in really small increments, and then is shaved back to ensure that it is true before the next layer is added. So the thing in this image that looks like a vacuum cleaner hose (on the RHS, near Jason’s hand) is actually a vacuum cleaner hose! As the work is planed back, the attached vacuum cleaner next to the machine starts up to suck up all the scraps so that they don’t interfere with the build.

Because the tolerances that the printer is working with are so fine, it continually adjusts and recalibrates itself. This is a ticker-tape of testing paper, that is continuously dotted with the two waxes as the machine prints. It’s not all this precise though. To the right of this (visible in Tuesday’s image to the right-hand-side, below the container of blue wax’s lid) is a little container with two larger puddles of wax that have been made during processing.

Once the models are ready they are pulled out of the machine, but they’re still attached to the build plate. To release them they are carefully heated, and after about 20 minutes they will just pop off the build plate, with no damage done. The printer puts down an extra bit of pink/purple wax to allow for this process.

After this the purple wax has to be removed. It is put into the small bath of acid (on the RHS of this image) where it is gently agitated while being eaten away at by the acid, to get all the superfluous wax out. The blue wax is apparently impervious to this solution. And the agitation? Say you had a more intricate design that had a large cavern inside the piece; something like that might be hard to flush out by just lying static in the solution.

Finally at the end of all this, you have your piece. Which you have to then cast in metal to make it robust.

In all, a little finicky for me, but if you like casting already then it’s a superb way to get a really reliable wax model. I’m a little more impressed by the idea of laser sintering, and being able to print directly in stainless, or even (the new kid in sintering school) titanium! 

(Gold is so old hat for additive production – Ted Noten did it in 2009 already…)

Previously: a rapid ring – part 1 + part 2, and the rapid prototyping course that resulted in this ring.

One thought on “a rapid ring – part 3”

Comments are closed.