The specs presented by Carbide 3D are ridiculously overstated - while not technically lying.
[I have been a machinist for about 12 years or so, now doing mainly electronics - power electronics and high-speed digital]
The specs they print are seemingly based on the stepper motors and pitch of the lead screw. When designing a motion platform, these numbers are interesting as they represent (to some extent) the best case scenario. In reality, the real world errors injected into the system guarantee that you will not achieve anything close to that resolution. The real test on a machine is to measure the actual movements in 3D, axis reversals, acceleration/deceleration, interpolation,etc. Usually this is done with a ball bar rig and it exposes the all the cumulative errors in the system. This is where the rubber meets the road.
Major red flags:
Lead screw: They are shit for this type of work. Ball screws are the only practical way to drive the linear motion.
Linear bearings: They are also shit for this type of machine as they are never rigid, the bearings will wobble. Linear guides on a ground/shimmed surface are the only practical way to support the linear elements.
Wood frame: Seriously, I cannot even comment.
10k RPM is slow for this type of work. Not unusable, but slow.
@blueskull think of much effort you put into a design from the block diagram to the schematic, to the PCB layout, to the final validation. The block diagram and first conceptual schematic are simple diagrams that show a concept. After you start looking into the implementation of the control system, parasitics, step response, stability, efficiency, etc, etc.....it gets real complicated real quick. The generic MOSFET symbol in the schematic can become a week-long search for the right balance of specs. The PCB layout becomes a maze of parasitic inductance and capacitance that works against you.
CNC is no different, the block diagram looks easy while reality is a giant challenge. Even (and perhaps especially) small parts like heat spreaders and PCB's are not a trivial challenge. For you stated goals, I have a few comments:
PCB Milling: The challenge is largely in how you hold and locate the PCB blank. It MUST be flat-flat-flat to get a reasonable result. This is not easy and a machine like the Carbide 3D has no vacuum system or another way to keep thin parts flat. Tiny variations in flatness have a huge impact on what you can accomplish. If your goal is to make high-current half bridges with big MOSFETS - no problem. As the features get smaller, the challenge increases exponentially. I have machined one PCB design and I did it on a $150k 5 axis machine. The challenge was entirely focused on keeping the PCB flat. Ultimately, using a vacuum plate (another $3k) and a fixture to align it for both sides and drill it (5-6hrs to work that out). Not easy even with serious tools.
HEAT SPREADERS: This is probably not a huge challenge for something like a Carbide 3D. Work holding is important as always and your tolerances will not be very tight. The programming of the G-code can be trickier than it may seem. I designed and machined a heat spreader yesterday and it took the majority of the day. I have an $80k Haas Mini Mil with another $40k in tools/software/work holding. Not exactly the challenge of my life, but not trivial at all. The tiny chips you will generate will get all over the motion system and any sensitive electronics. be prepared to clean constantly or fabricate some shields.
STENCILS: This may be the hardest one of the three. Milling very thin material is hard - not for the machine but for the machinist. How do you hold it down while a helical tool is trying to pull it up? This is why stencils are cut with non-contact lasers. Mechanically cutting a stencil with any mill or any quality will be hard to do regardless of the size of the designed features.
If you get a low-cost desktop CNC - be prepared to spend many hours fiddling with a steep learning curve and a fiddly machine. Many times it is very difficult to tell if your problem is a limitation of the machine, your skills, your tools, or the process in general. What appears to be a quick PCB, heat spreader, etc....can go on for days.
Yesterday's project.....