This is definitely a case of a mechanical engineering dropout(almost certainly due to it being too hard) picking up a couple ballscrews and linear rods, realizing they are heavier than plastic, and thinking: "Well these seem rigid enough, why can't I mill with it?".
What the dropout doesn't realize is that cutting forces are not only orders of magnitude higher than he thinks, but all components always imperfect and on top of rigidity issues you also get accuracy/backlash/tolerance issues.
The way
real 4 micron machines do it is as follows:
- Get some cast iron or machine-specific epoxy granite
- Triple that amount
- No, triple it again
- Bolt that to a 20cm thick reinforced concrete pad
- Embed a bunch of channels for heat transferring fluid into the base and all large moving parts
- Attach a high heat capacity chiller-heater combo to keep the entire machine at a set point(usually 1-2C lower than ambient)
- Place very oversized, over-rated components on all linear axes(ballscrews, linear rails, all rated at several hundred kN higher than your estimated loads)
- Preload the hell out of them(impossible without rigidity)
- Place linear encoders directly on the translating frames, not at the input(which already has encoders, because you're using very well tuned AC servos)
- Spend a few months in R&D tuning the several control loops
- Design, build, and install a zero-tolerance preloaded spindle(which results in ~1-2um of tool TIR, never perfect)
Congratulations. Now your machine starts at $1 000 000 with no options like tool carousels, work piece pallet systems, etc. You'll want those, too, because you just built a machine that needs to be running 24/7/365 to pay for itself in just a few short years, and downtime means bleeding money.
I'm willing to bet $100k of their money that you could cause 100um of deflection by pressing on the collet end with your pinkie finger.
A few other problems:
- It's too slow for 3D printing. You need fast retracts and rapid moves for 3D printed parts to look clean - even for the simple reason of ooze, which is now a standard feed-forward calculation option in most slicers. Also part cooling. Not to mention printing slow means you're... printing slow, and any cheap $200 kit can print faster and cleaner.
- I don't see any protection for that 2W laser, which on top of being multimode and hard to focus, as mentioned earlier, is extremely dangerous optically. So on top of being near useless(maybe for burning letters into leather or something), a single unlucky reflection of a slightly shiny surface can result in permanent, irreparable blindness. The reason cheap CO2 laser cutters get away with large transparent windows is simply because polycarbonate is opaque to 10.6um light.