It'd not so uncommon at all, there's at least one portable mill sold that has a canted band. I've watched it mill logs at shows, but the name excapes me right now... lol AND, i'm too lazy to go look through my picts to find it.
Rob
Well it's very interesting to a mill geek like myself either way.
Out here, the band headrigs ONLY deal with the big logs, say 20-24" diameter and up (the now-unused one where I work was built to handle 5' Cedar logs), which are then squared up and cut into big cants or slabs and subsequently fed into a gang edger to produce the lumber. The big mills that produce a significant amount of lumber all feed any smaller logs through a Chip-n-Saw canter and/or twin-band system to square and cant the logs before splitting in the edger. Headrigs are just not economical for dimensional lumber production anymore unless you're lucky enough to have access to huge timber, and one of the big reasons that you guys south of the border have had such a hard time competing with us on that turf is because we were quicker (necessity being the mother of invention!) to adopt such systems; they've been in use around here for over 40 years now, milling the smaller Lodgepole Pine logs that previously were thought junk and not even included in the timber inventory when everyone was going after the first-growth Douglas Fir. Headrig innovation, for better or worse, hasn't come very far up in this neck of the woods since then, other than the obvious modern automations and conversions to computer/PLC control, but the machines around here are pretty much the ones installed when the existing mills were built mostly in the '60s.
Found another excellent video of a slanted band headrig, this one is a doublecut band:
http://www.youtube.com/watch?v=d_jjrv9X5UU
I think this sawyer was a :newbie: though! Notice in the second log he's working on, he ends up getting the pith way out of center by the time it's down to the last cuts, and the last couple boards and final cant are so sprung and crooked they're worthless. May as well have dumped them down the tipple belt too. I know the odd log is bound to spring on you once in a while no matter what, but that one appeared to be so nice and straight.
Doublecutting is the only hope of really making a headrig compete in dimensional production, but even still, those two logs would have gone through a chip-n-saw and edger and be milled down to boards within a matter of a couple dozen seconds at most. Recovery is noticeably less with such systems, but is more than made up for with speed and efficiency, and right now chips are worth almost as much as studs anyway!
Having said that, to me there's just something beautiful about taking your time and milling a log to its utmost potential with a headrig. More fun to watch the log turn into boards that way, at any rate. A good video of some vertical sawing like I'm used to seeing:
http://www.youtube.com/watch?v=mwg1dZokRbE
I couldn't find a portable slanted band, but I did find a slanted double-circular portable mill, which has impressed the heck out of me:
http://www.youtube.com/watch?v=VcwFwkfTpmE
