Happy New Year everybody!
I’m on step #4-C1; attaching my completed gantry assembly to my Y-axis carriages. The Left hand side of the gantry fits the left side carriage perfectly, but on the right side there’s about an 1/8” gap at the end of the carriage weldment (see photo).
Everything is only finger tight right now, but I was concerned that just “sending it home” could introduce a bow into my gantry assembly. Has anybody else run into this?
Can you pull into place by hand? if so, the tube is probably just leaning in toward the bracket do to the stantion plates not tightened yet. Will be ok once you level, square table then final tightening of bolts.
I can close up a tiny bit of that distance by hand, but only because the big bolt on the end of the gantry tube is still kind of loose. The bearings are still loose, as well, but the weldment is crooked; it’s not flat across the top. See how it sits flat on the tube, but then it diverges as the support bracket piece departs the tube?
It will be ok once bolt is tightened then, that will not put a bow in the tube. Put a straight edge on top of tube see if tube is true, then tighten that bolt see if it bows the tube. Bet it don’t.
I think you’re probably right. If it deformed anything, it would be the bottom of the gantry tube, and I don’t believe that anything really tracks off of the bottom, though I probably ought to contact Langmuir before I go cranking down the bolts. 
Any progress on table?
So, yeah. I’m not sure how I feel about it all, but I went ahead and did the whole Y-axis/gantry alignment routine. The bracket and gantry tube just sort of “deformed” into shape. Both seem to be made from very soft material. I went through the adjustment procedure a couple of times, and both times wound up with the same result.
I would preload the adjustable bearings, then tighten the gantry, then the bearing blocks, and lastly the Y-axis tube brackets. I followed the directions to the letter, and both times after snugging the gantry/bearing blocks and tubes I would have new free-play in the carriages again, so I would add more preload to dial that free-play out, which results in a little bit more “drag” on the carriage than I would like.
Granted, I’m not binding at all, but the carriages aren’t as light as they were before the adjustment procedure. I guess I’m just not sure how a properly aligned and preloaded carriage is supposed to feel. The instructions just say “move freely”. It moves freely, as in without bind, but there is some drag…
You will know once you run the break in file and jog everything around if bearings will need readjusted or not. Just remember that the bearings will not have full contact at same time along the tubes from one end to the other.
Well, basically, after the initial adjustment, I had 1 bearing on each block in contact, at least, with the tiniest bit of drag. After I tightened the blocks, and all the tubes up, the gantry moved like butter, but I had areas in the travel where both bearings on one block might not have contact at all, anymore, so if I understand the instructions correctly, that’s where they want you to go back in and add more preload.
Prior to adding more preload, you could just sort of nudge the gantry and it would glide all the way from one end to the other with it’s own momentum. After I dial more preload in, it moves easily, but it no longer glides on it’s own momentum.
It’ll probably be ok once everything breaks in, but I really liked the way it felt before I added more preload. I’ve never set anything like this up before, so it’s hard to know. I don’t know how much torque those little motors put out, but I know they only engage in a nylon nut, right!?
The only thing I can liken it to is setting up new wheel bearings on a car. If you spin the wheel and it freewheels on brand new bearings they’re too loose, but they’ll do that when they’re broken in.
Don’t add any more preload to the bearings, run the table for a few minutes and see if you get binds and that torch is square to work surface. Lube bearings with 3-1 oil before running table.
Thanks Richard for your help on this. I was going to add any more preload than I already have done. But, basically after tightening the gantry, bearing blocks, and the y-axis rails, I only had bearing contact on the tops and insides. Good tip on the 3 in 1 oil. Hopefully I’ll have the table running the break-in procedure by the end of the day…
