Alright! The promised update...
Last evening I spent about 2-1/2 hours riding herd on the milling of the two plates. I found, in my junkpile, an old broken, 18mm thick, particle-board panel from some crap piece of furniture long lost and forgotten. The tiny 1/8" single-flute endmill (from Ryan's shop) worked beautifully though I had to press off the little plastic depth collar to get enough bit showing to get through the panel. Milled at 10 mm/s and 5mm depth of cut and finish passes on all pockets... a slow procedure but quite accurate. I was thrilled...
So, this morning I started assembling one of the end plates. Mark's article leaves out a bit of detail, especially the spacers and bits to locate the wheels and idler bears, relative to each other... and the edge of the table. Took a few SWAG's at things and printed off things I thought it needed... and finally arrived at a freely rolling gantry on a 2' x 4' piece of plywood I had. Set it up on a short, roll-around, wire-shelf unit my wife had purchased somewhere along the way and I now have something I can walk around and touch/probe/prod/ponder what needs to be addressed next.
Obviously, I need to make a lot of adjustments now... I wasn't expecting the belt to run so close to the table edge but that does appear to be the case with Mark's machine as well, judging from pictures in his article. i'll also probably change the plywood bed to MDF... I have a 4' x 4' piece over in the other house that I may cut a bit narrower. Mark used a 32" interior door... probably a better and lighter choice but I don't have one in my stash. I'd like to keep it on the smallish side but at least 6" more than the 24" width shown here... 30"-32" wide and 48" long should be just about perfect, large enough to comfortably place a DTFB sheet and vacuum hold-down setup, like Mark's. I did opt to merge the MPCNC tool mount with Mark's Z-slide setup so that any MPCNC tools could be mounted... as long as they fit between the rails. Mechanically, now, the basics are in place and I have something to play with. I'll belt it up and wire it as soon as I think it sound enough to proceed.
I don't know yet how necessary the lower wheel assembly is... but the plate DXF already had the slot and I had the wheels, bearings, and hardware to populate it. It shouldn't hurt anything so I'll go with it for now... I may just put a wing-nut on it and slip it up "close" to the bottom of the table edge, just for grins.
Anyway, there it is. Thanks, Mark, for sharing it with us. You hit your target dead-center IMHO... wanting to "see how inexpensive a machine [you] could build." I think this is really gonna be a neat machine... the simplest and least expensive foam cutter setup I've seen to date.
Great job, Mark!
-- David