microcutting
Comparison of micro-waterjet, laser, EDM, NC, ... cutting
micro-waterjet
MicroMAX at OMAX Demo Lab - https://www.omax.com/omax-waterjet/micromax
Nozzle: 7/15 MAXJET5 Minijet Nozzle with 0.007" ID diamond orifice and 0.015" Roctec 500 mixing tube
Abrasive: 240 mesh Barton HPX garnet with a mean particle size of 60 um at a flow rate of 0.12 lb/min
Pressure: 50 ~ 55 ksi
Cutting time: 3.1 min
solid-state laser micromachining
ultrafast laser micromachining
EDM
Full-scale Toolpathing
We toolpathed the microspline part at the full ~2" long scale. This would be cut from a stack of six sheets of 0.03125" thick brass layered on top of a 1/16" thick piece of steel. We added slits in the frame to avoid pre-drilling any holes. We also removed all of the tabs. This may prove to be a bad idea but it allows us to get a sense of the speed of Wire-EDM vs uAWG without having to do a lot of pre-processing. The total path length of the full scale toolpath is 52.5 inches. With an expected cut speed of at most 0.22 inches/minute, the expected cut time is approximately 4 hours.
1/3-scale Testing
Given the long machining time, we ultimately decided to do a 1/3-scale test cut from a stack of 0.01" brass sandwiched between 0.25" aluminum. The perimeter of this toolpath measures 17.5 inches. With an expected cut speed of 0.18 inches/minute, the expected cut time is just about 100 minutes or 1 hr 40 mins.
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.
Fablight fiber laser
Machining time: ~5 min
Cost of machine: sheet only machine with the 3000 laser is around $80,000, and the tube & sheet is around $90,000
Machine settings:
Sample photos:
After burr removal
The brown seen on the edges of the piece are burn marks where the machine cut.
