It came up in another thread that some people were weighing the B9C vs. the Form1 as a place to spend your hard earned cash. I considered it too and ended up pretty far on the Form1 side of the fence, but I’m curious what criteria others judged by.
The B9C is interesting, but there does seem to be some real downsides (aside from the size of it and that it looks like something I’d make in the garage myself ;-). The Form1 is using a laser galvonometer setup, so they’re able to plot two endpoints on a ‘line’ drawn with the laser. The upside is that while the position of the points is limited to the resolution of the DAC and positional accuracy of the scanners, the line that is drawn between the two points has the potential to be essentially ‘analog’-- it’s basically free of ‘resolution’ limits as the mirror sweeps to a new position. (So the endpoints of a line in a slice are subject to the units positioning resolution, but the sweep of the beam between them is effectively infinitely smooth. That’s *if* they’re plotting endpoints and letting the galvos slew to the new position. They may be running the DACs in more of an absolute deflection mode (taking each ‘step’ one ‘pixel’ at a time), but if they leave the laser on the mirrors still move and ‘sweep’ the beam, so you still get an anti-aliasing type effect from that. Either way, it still seems like it would give superior performance vs. a pixel based exposure from a DLP projector.)
The B9C is using a commercial projector focused in a rectangular area for activation of the resin, so if it supported an HD projector (1920x1080) and you want 50 micron resolution along the X and Y axis… 50 microns = 0.00196850394 inches… So 1920 x 0.00196850394 = 3.77" and 1080 x 0.00196850394 = 2.12". That’s a pretty small build envelope compared to the Form1 (4.9" x 4.9"). With the specs on their webpage, they claim only a 2.02" x 1.51" envelope at 50 microns now-- so that would work out to be a 1024x768 (XGA) resolution projector.
One neat thing is that the B9C could expose an entire slice at once which is pretty cool, so it might be able to print faster.
Comparing the B9C’s usable build space with a 50 micron ‘pixel’ resolution (1024x768 projector) it covers ~3 square inches vs. the Form1’s ~24 sq/in. That really puts them in different classes for the kind of things I want to do. If you just want to make little pieces (like jewelry) the 2"x 1.5" working size might not be a big deal, but it kills it for me… Put another way, the B9C needs to be at least 8x faster than the Form1 for me, because I can array muliple parts in the Form1’s envelope and print all at once vs. needing to make multiple prints with the B9C. Which is better likely depends entirely on what you plan on using it for…
One thing I am curious about on the Form1 is what it’s “limited” by. If I were to wager a guess, I’d assume that they’re using a 12bit DAC (or ~12 bits of usable resolution anyway) for the scanners-- so that gives them positioning accuracy that’s presumably 4.9" / 4096 = 0.00122", which is really close to 30 microns. Judging by the pictures in Bunnie’s teardown, it just looks like they have off the shelf Chinese sourced galvos and deflection amps. I wonder if there would be performance gains to be had by upgrading the scanners (say, to faster/higher precision Cambridge Tech galvos and drivers) and some optics on the laser to focus to a tighter spot (and/or higher output to pump out the same amount of UV per unit area given a faster scanning rate). Alas, there’d likely need to be firmware changes made to take advantage of it (so probably nothing we could “DIY” hack), but you can see where a Form2 might be achievable with a similar architecture and just more expensive components.
Anyway, the B9C seemed to me to be at a real disadvantage for working envelope at similar resolutions and the size and “hacky-ness” of the machine really turned me off given the price point (higher than the Kickstarter priced Form1 I decided to go with). I might need to try their resin, though. 
