Well, the box from MTW arrived a few weeks ago, and last weekend we had the time to sit down and check the components. One of the two sets of 8mm rods appears to have just enough of a bow in them to be unusable. This morning I've filed a ticket with MTW to see what can be done about this, but, meanwhile, I have put the Misumi extrusion corners to work.
It struck me as odd how, in the Build Guides, a complicated blind-drilling and special Torx fasteners are used to fasten to cross-members to the upper frames. This, and the use of printed braces across the corners seemed to me, at least, to be a strange approach to which an inexpensive solution is already available - extrusion corners.
The order of assembly I followed is definitely not standard, as the constraint problems to be solved are different for this assembly technique. The steps below achieved the best results without too much fiddling.
Start with four extrusion corners. Check they are square, and smooth off any molding flash with a good file so they are clean and completely square.
Next, take the cross-members. Install an extrusion corner onto each end of the cross-members loosely enough to slide into position using 5mm X 10mm SHCS with a flat washer.
Since I installed my corners on the inside of the frame, my next step was to measure from the end near where the corner was attached a distance of 80mm. Tighten the corner gently (not fully, just enough to hold them still) such that its vertex is at this distance from the end. Repeat with the other end of this cross-member and another corner. (If using corners on the outside, measure 60mm.)
Build the other cross-member exactly as this one. Once this is completed, check your corners are on squarely, and all are at the same distance from each end of each member. Adjust as necessary.
Now it's time to assemble the uprights. Attach one upright to each end of a cross-member with 5mm X 10 SHCS with a flat washer on each. Tighten these screws gently.
Once both uprights are in place, use your square and check they are square by placing it in the vertex opposite the extrusion corners. If adjustments are needed, be sure to check both squareness and distance. Once adjustments are complete, tighten and recheck.
If the corners are placed correctly, the outer edges of the uprights will be at 60mm distance from the outer ends of the cross-member, and the inner edges of the two uprights will be 260mm distance from each other.
Repeat these steps for the other cross-member and uprights, then, when all is checked and squared, place the two assemblies side by side resting on the top surfaces of the cross-members, with the uprights sticking up. Compare these assemblies to each other - they should be identical in all respects. If not, check, tighten, recheck, and adjust as needed. The 260mm dimension is the crucial one as this is the width of the frame to which the uprights must attach.
Once both upper frame assemblies are built, check the printed parts for the lower vertices. The inner and mating bottom surfaces should be true, straight, and free of any plastic flash which might interfere. Trim as needed, then proceed.
Now trap a T-slot nut in the forward facing and outboard sides of each upright and attach the lower vertices onto the ends of each upright, trapping the T-slot nuts, using 5mm X 10mm SHCS. (On the parts I had, a flat washer would not fit in the recess, so I tightened snugly, but not overly tight. This should not be a big deal.)
When installing the vertices, it is important they face the same direction on both uprights. (Yeah, I started one backward... caught it before I was done threading up, though.) I used 5mm X 10mm BHCS (button heads) with flat washers to fasten the sides of the vertices to the sides of the extrusion using the already trapped T-slot nuts.
The resulting assemblies may now be mated to the lower frame using the T-slot nuts already trapped there for the purpose during assembly of the lower frame. I used 5mm X 10mm BHCS with flat washers here, and found them to be of positive benefit - my 3mm hex key had a lower profile and better clearance on the inner side of the vertices than did the 4mm used for SHCS. This allowed for faster assembly with less re-positioning between wrench turns. At this point, tighten the screws gently.
Once both upper frames are in place, check for square with respect to the lower frame and with each other. If it is not possible to square them in both respects, something is wrong - check your upper frame assemblies and the lower frame, and adjust as needed to bring both into true squareness before proceeding.
Finally, integrate the two upper frames by installing the end supports to couple the cross-members. Remember to trap the T-slot nuts needed before installing the end pieces. After both ends are in place and loosely fastened, check again for squareness and that the cross-members are running parallel to each other.
Tighten and re-check. Adjust as needed.
Once everything is assembled, it should look something like this:
Here's a side view:
As can be seen, the Y-Axis slide is not yet mounted on the support rail. This is because we do not yet have the parts in hand. Once these parts are ordered and arrive, the real fun will begin - installation of the motion components!
At least now it's starting to look like a MendelMax! Resolution of our trouble ticket and getting the Y-axis gear in hand will get us to the point we can start installing the rest of the mechanicals.
From there, it looks like motors, leadscrew development work on the Z-axis, (yeah, we're experimenting here as I may have already mentioned), and then electrical and electronic controls will complete the assembly.
Tony has diverged, and is working his hybrid Max/Max 2.0 design, so I will be following his work as he progresses. I am intrigued by what he has put together so far - it has the potential to be a very solid design, and one that existing MendelMax users could easily convert to if desired with just a few printed parts, some extrusion corners and a bit of re-assembly.
That's it for now. Next time, look for info on the installation and setup of motion components.
