Edward - thank you so much for your wonderful creations and ideas!
I would be very interested in a laser cut steel precision bracket. If we linked up 4 (15250) extrusion holes in the new bracket instead of just 2 it might take out the c-clamp and flat edge assembly steps I used to make sure the two pieces were flat and square in the middle and at both ends while tightening everything down.
I can supply a DXF after I test the print it to verify it fits.
Here are the assembly steps I used below.
For the clamping jig I used a wooden spoilboard on top (lengthwise going back to front), The clamps all had rubber jaws so I could clamp to the 2020 directly.
1. I installed all the screws through the existing stock Shapeoko 2 endplates simi-tight and the ones into the tapped 12500 holes and tapped makerslide completely tight at both ends of the Shapeoko.
2. I installed the jig and clamped the spoilboard down loosely at first at both ends and added clamps at the corners of the bed nearest me. Hanging the Shapeoko off the worktable by about 3 to 5 inches helped me install the clamps easily. The table edge allowed the bed to just lay flat. The tilt caused by the 2020 and clamp at the back wasn't a concern.
3. I adjusted the two extrusions by feel, tightened the jig a little more but not completely.
4. I installed the small printed plate, installed the bottom screws into the t-nuts hand tight and tightened the two top screws completely tight. This squared up the bed (in the XY plane) and the second time through the whole Shapeoko sort of snapped into alignment probably overcoming the tension in some hand tight screws.
5. I tightened the clamping jig pretty tight checking for gaps between the 12250 and the 2020 util they were gone. This fixed the z plane
6. Then I tightened all the screws that went into the 2020 T-nuts in both end brackets and the middle brackets.
7. I removed the corner clamps and I turned the Shapeoko around and repeated 2-6 again.
8. I then removed the jig. Checked things with a square, no adjustments needed.
That let me take all the "slack/twist" out of the t-nuts/fasteners/brackets and left a very level bed and a very Squarely aligned Shapeoko 2.
Considering the closed bed you need, you might be able to use a 3 series 15mm x 15mm on one side and the same 15mm x 15mm along with a 15mm x 20mm one on the other?
I don't know why I seem to have a 15mm obsession, something thicker or thinner would probably work just as well.
2 x HFS3-1515-500
1 x HFSQN4-1520-500
The problems I see are:
1. attaching the 1520 since it only has side channels and no slots top/bottom but perhaps the do-hickeys would be enough?
2. The slots on standard series 3 are only 3.4 mm so you have to use M3 bolts and tiny T-nuts.
Putting the Shapeoko 2 in an enclosure is a great idea. I may do it myself but I would have to design it to still be able to easily remove the end panels so that I can continue to do composite mills of one long workpiece against a fixed fence for sign making, furniture, etc. I have done 2 and 4 foot long workpieces already. Your open ends design of the Shapeoko 2 bed made that kind of work possible and it isn't that hard to mark and move the piece very precisely one foot at a time against a marked fence. Repeatability was easy with the homing switches, but a light tool mark demple on the fence worked fine before I upgraded to homing switches. I still have to manually jog the Z origin of the workpiece into place.
I am thinking about an enclosure design using "trapped" panels in stock series 5 or series 3 extrusions. Could a 550mm x 472mm x 6mm panel slid into the existing 2020's slots add a bottom to the enclosure and eliminate the need to make a 550mm bed? I suppose it would probably collect a lot of debris over time.
My first approach to the table was almost exactly like yours, I even fabricated a bunch of printed brackets with slot filling tabs but when the stock plate hole pattern lined up I had an "AH HA!" moment and abandoned them to my scrap pile of printed plastic.
Here are some png renders of the brackets exported out of Openscad just for history sake. They were printed in PLA with 1mm thick top, bottom, and walls and infilled at only 25% between. Then I used a steel file to clean them up and ensure a tight fit.
15x20x20 to bolt the 15250 edge to the 2020 rail. The screw heads barely clear each other so you have to drop in both screws first and then tighten both at the same time, working the part into place using the little play you do have.
A 20x20x20 to use under the bed just like your angle ones. It is also designed to fit the END of the 2020, like and end cap but attach 2 pieces at right angles. A 3 sided or 14mm offset one might be useful in fabricating a 2020 based enclosure. Perhaps I'll design and print some.
For causal readers: WARNING I ABANDONED THE FOLLOWING BEFORE TESTING THEM..
I also designed but didn't fabricate these double hole brackets:
These would work in the middle to join two plates.
These are for anywhere except the middle.
Shapeoko 2 #3181, Protoneer Arduino CNC Shield, Step-Stick 4988s, GRBL 9b+, All Aluminum Bed - Misumi HFSQN4-15250 extrusions, Dewalt DW611, Precision Think & Thinker, Collets.