Micromachining using Zund G-3 L-2500
Despite being a very large-scale tool, the Zund was surprisingly effective at micromachining with its 50kRPM router spindle. To fixture the stock, we first faced a sheet of aluminum to provide a rigid surface. Then we applied PSA tape to both this surface and the underside of the stock. We burnished the tape using a small stainless rod. Then we applied CA glue to the tape and bonded the stock to the substrate.
Using a .030" diameter end mill with amorphous diamond coating (Harvey Tool 72030-C4), we machined the flexure from .020" Aluminum 2024 sheet in 2.5 minutes (comparable to the waterjet). 300um step down, 20 mm/s, 50kRPM.
Here is a 50% scale flexure (.010" beams, .015" gaps) machined from .020" thick Aluminum 2024 sheet using a .015" diameter end mill with amorphous diamond coating (Harvey Tool 72015-C4). This took about 8 minutes, but I think could be run faster.
Here is a paper about micromachining aluminum using tools with diamond-like coatings: Diamond coatings for micro end mills: Enabling the dry machining of aluminum at the micro-scale, Heaney et. al.