Post date: Feb 24, 2014 1:18:25 AM
...and more!
Most prominently the new table is bolted down. Furthermore, the T-slot table is bolted on top of that, so I can actually resume milling stuff:
You can see the front and back views (note the lovely metal roofing screws holding the back plate on- classy!) above. I've even gone so far as to level the table, since it had been remounted. It turns out it had shifted quite a bit- the outside slots haven't even been touched (they will be if I ever need to mill something that requires support that wide). Leveling took much less time with the new spindle than previously!
The new Y axis is incredibly smooth- the leadscrew is aligned just perfectly (well, pretty close at any rate), so it turns with negligible resistance. Unfortunately, somehow (despite CNCing the pattern and holes), the stepper is not perfectly aligned with the leadscrew shaft, so I'm still using the old rubber tubing coupling. On the up side, it works just fine for low-torque applications.
Always a favorite feature on axes: limit switches! Yes, I have limit switches installed on my Y axis still, except this time they're done better, with no wires trailing along the sides of the machine. They're hidden under the right side of the table- with "right" as shown in the left image above. They'd be on the left of the right-hand image.Just imagine they exist between the two images. In case you lack imagination:
There's an extra aluminum rail that runs along the bottom of the table. The switches trigger when they run off the end of it, which is good, since I don't want my table crashing into my stepper.
Finally, a little work on the Z axis. During the course of all this other work, it became apparent that the Z axis wasn't perpendicular to the XY plane- maybe a quarter inch of Y-dimension travel over the course of the Z axis, which is kind of a lot.. The simple solution was to shim the bottom of the Z axis to force it out a bit. Conveniently enough, a couple washers made it pretty darn close to perpendicular (at least as far as I can tell with my improvised right angle- aka, the old table).
It's shimmed out maybe 0.125" (I think the washers were ~0.128", but close enough). I didn't really do any tests to see if it gives a nicer finish, or cuts nicer PCB traces, but at least it appears to be much more square.
As far as replacing the axis goes, I'm so far quite satisfied. I have yet to check how close to perfectly aligned the Y axis is since bolting it down, but it at least looks good (though I realistically probably couldn't see the difference between 85° and 90°, much less 90° and 90.1°). At a minimum, it slides so much better than the previous iteration (remember how that was shimmed up to prevent it from wobbling- ie, had LOTS of friction?). I can now do rapid moves around twice as fast- actually faster, though not consistently. And by that I mean that 0-42 inches/minute works just fine, 42-66 inches/minute is kind of sketchy, then 72 inches/minute is fine again. Go figure- I've read that harmonics can creep into steppers/leadscrews and cause problems, so maybe that's the issue. In any case, I don't need to move that fast, so I just limited it to 42 inches/minute peak.
The X axis is coming up next for replacement! Or maybe getting the Y axis stepper properly aligned with the leadscrew... one of those two, in all likelihood.