The reality of a semi-automatic printer like that with or without vision is that they are reliant on every single PCB aligning up with the stencil perfectly for each print based on how the fixture held the first PCB. The reality is that isn't always something you can rely on. Hold the board by the edges and the PCBs can vary just a little, align with holes and they need to locate in such a way that the pins don't come thru the board and are enough to hold the PCB firmly, thin boards or ones with no holes then become tricky. Some semi-auto printers with cameras let you check alignment for every print e.g a Miniko, TWS SR2700 or PBTs offerings which helps. Camera alignment on a semi-auto doesn't in itself make it more accurate, its still you twiddling dials and looking through apertures to the board beneath (unless you have a mylar screen type) that still has its very obvious weaknesses. What the camera certainly does help with is getting a view exactly perpendicular without leaning over the board in a fashion that may not be comfortable or possible.
However they are still much slower to setup than an automatic printer, it all looks very slick in the video but that's a lot of bending down and reaching under and how often does a stack of panels just drop into a fixture perfectly secure just like that? I also really have no idea how anyone can actually sell that design in Europe with all those moving parts your actually supposed to put your hands under.
However alignment for every board is only half of what an automatic printer offers, they also make up part of an automated line, they (can) inspect the print for solder deposition consistency, they typically take 29" frame as standard so print quite a big board (much harder with manual alignment) they can store the locations for support pins and then laser designate them or even place them for you, options like RED-E-SET/Gridlok actually exist for them (the semi-auto versions are no longer). They are quicker to setup/changeover. Stencil underwipe/cleaning is basically standard.
However to your question "at what point?", well at the point you can identify not having one is causing problems on the boards you manufacture. I probably build similar volume, we still do it with manual/semi-auto printers without vision. Like you we avoid BGA, 0.5mm in opinion is right at the limit of manual aperture alignment, we have a few 0.4mm pitch ICs and they are not fun, just about doable, but not fun. We're at the point we can say we do need an automated printer so I have done some of the legwork on the options, current circumstances however aren't exactly conducive to investment are they
. I don't think there are any really bad choices but there are some that are clearly not as good as others.
Desktop vision semi-auto NEW : ~10-15k
2nd User DEK: ~ 10K-45K. Really depends on the model, features and age but built like tanks and in the UK at least, really not an issue to get serviced even on contract.
Standalone vision semi-auto NEW (PBT FA23/Reprint R23): ~ 20-25k there is also an auto alignment version of the FA23 which makes it a unique hybrid.
Chinese Auto NEW: ~25-35k depending on brand and where you are buying it (note they all have the exact same weird weakness, accept a 29" stencil but only print a board you would expect to be able to print in a 23" printer)
ESE: 35K+ these printers are pretty affordable and I've seen lots of praise too (
https://www.elite7group.com/ has a price right on the site)
DEK NEW: Never had a formal quote but it has been suggested a deal can be done at ~40k for an intro model, I'm assuming that's a Chinese built E-series.
Speedprint: 50-60K start. Seen a few meh comments but Europlacer/Speedprint are very nice people to deal with, even according to those who say meh about the printer.
MPM: 60-80K
SJ Innotech: 80k+ , they make no bones about being a high end large format specialist.
Mycronic MY700 Jet printer: Somewhere north of 100k, 70-80k might get you an official factory refurb. These have interesting economics, some swear by them others don't think it adds up.