Thanks all! Glad it might be useful. I've uploaded the
svg, dxf, and vcarve files hereI've started using this clamp in a kind of manual assembly line process for small projects out of 3/4 boards. I have some things that take 8" of vertical board space and have toolpaths that require 3 different endmills, so I'll take a 7' or 8' board out and mark on the left edge in 8" increments (plus a small margin for error and to leave enough material between to withstand clamping pressure) all the way down the board. Each mark will take a few turns lined up at the origin point. I'll put in tool #1, line the board up at its first mark with a mark I made on the left clamp that corresponds to Y=0 (the clamp side is always on X=0.. shift it over in fabmo if you need to for larger bits), clamp, run job... unclamp, move to mark 2, clamp, run job... unclamp, move to mark 3, run job... etc down the board. Then switch to tool #2, line it up again at the first board mark, clamp, run job... unclamp.. etc down the board again. 1 complete pass of the board for each endmill for any number of parts (or boards for that matter). That way I only have to change each endmill once. Having that custom Z-zeroing macro mentioned earlier in the forums and an aluminum plate makes precise zeroing to the top of the stock really easy too.
This suffers from some accuracy loss between tools because of the sight aligning with the Y=0 mark. A lot of my cuts are fine with that level of accuracy, but I have an idea to improve it pretty easily for others in the near future.
Also, if your endmill edge moves beyond your stock in your toolpath, just stick some same-height spacer strips as left and right spoilers between the clamp edges and the workpiece. I cut a bunch from my MDF scrap from making this. Remember to shift the X origin right by the width of the spacer in fabmo before using though.
I'll try to answer the questions:
I did not make this on a handibot, but don't see why you couldn't with the large material jig. Actually, I was cutting a large material jig on a shopbot alpha and used the time I had on the machine to crank one of these out too. See the crv in the link above... but it's not tiled - definitely change up your job parameters.
Also - you might consider a rabbet on each clamping side edge for sawdust. I didn't because I usually blow it out anyway when changing things and I wanted the option to do very thin aluminum plates or even PCB boards down the line. The file is bottom facing up, so they'd be easy to add.
Regarding downforce, I've only been using square, jointed stock so far. With that, there is absolutely no problem. I have to apply downward pressure when applying the clamps, because if it's floating just a little bit, it's nearly imposible to push it vertically once clamped. Seems like it could get to be an issue with live or very non-square left and right edges. In that case I'd probably use a couple of wood or aluminum downclamps on the spoilboard top and bottom, then use the clamp left and right.
Really interested to see more of the extended Y-axis. I backed the Maslow CNC project thinking it could be a good cheap machine for those rare (for me) large sheet projects, but if that doesn't work out then the extended Y gets a lot more tempting.