Introduction: Tiny Metal Balloon
Tiny Metal Balloon is a solid aluminum balloon shape held up by steel wire. It's a small project made possible by the CNC lathe. This would be hard to create without a CNC (almost impossible), and still hard to create even if you're using a 3-axis CNC mill (because, part flips and workholding). And yes, I know CNC lathes are hard to come by.
However, if you're just getting started on the CNC lathe, here's a quick simple project that produces a good birthday gift. It's always somebody's birthday.
Step 1: Necessary Tools & Supplies
- CNC lathe – with facing and general turning tools. I used a Haas VF-2SS at the Pier 9 Workshop
- CAD/CAM software – I used Autodesk Inventor, but Autodesk Fusion is free and just as good!
- 1.5" dia. aluminum stock –at least a 3" length of it. McMaster has it. Always.
- Steel wire – and some good old pliers (preferably not old, and preferably needle-nosed).
Here are all the final files I used for this, bro.
Step 2: Some Tricky CAM
When I said this is simple, it's because I broke a lot of balloons to make it simple.
The CAM is actually a bit tricky, because if I had the fat end of the balloon sticking facing the chuck/stock (i.e. machined the smaller end first), the available turning profile tools weren't thin enough to create the shape of the balloon. With the right tools, this wouldn't be tricky, but I had to work with what I had, and that was a 35deg finishing general turning tool. Grooving tools didn't help.
I was able to get the tool deep enough if I had the smaller end of the balloon facing the stock (see image), but then a new problem arose. At a certain point, the work piece would be a mostly finished balloon just hanging by a small (like .100" diameter) neck.
So all these broken balloons are trying to find the right spindle speed, feedrate, and toolpaths to get a nice finish and not break the neck.
This seems obvious now, but in the end, I artificially broke up the tool path so that creating the neck is the last operation.
Finally, I don't part the piece with a parting tool, because that has almost always resulted in the part falling somewhere deep in the machine. I can just bandsaw it off.
No matter what I just said. Make sure you CAM this, to simulate that the tools you'll specifically be using won't collide with anything. (Even if you're at Pier 9, it's very likely the tools have changed since I've used them. It's CNC mantra to never assume anything.)
Step 3: Machine + Finish
After you've set up your stock, zeroed your work offsets, you're ready to machine! (results may vary). After I machined it, I polished it with a scotchbrite fine grit wheel to give it a little more sheen.
Find some steel wire and pliers and work the wire until it balances but looks like it's pulling the "string."
Then, give it to a friend who likes tiny versions of things.
Step 4: Polish to Make It Super Shiny
Follow my steps in one of my other instructables: https://www.instructables.com/id/Polishing-Machined-Aluminum-to-a-Mirror-like-Finis/
and polish the balloon to make it look like mylar.