VMC Z axis misalignment: What are my options?

This is making a very long story very short but I recently completed a long distance move of my shop and have finally got things up and running again.
This has been overall a terrible experience for many reasons but It's basically over and I'm trying to move ahead. I feel like I've been screwed over by almost everybody I've paid to do anything. At the very least I've been treated very poorly.

The problem machine is my 1 year old 30x16 linear way VMC. Got it craned in this week (I'm on the 3rd floor), fired it up and leveled it. Table is dead level (.0005"/10" level), no twist in the bed, looks good. Put a tenths indicator in the spindle to sweep the table, not good. Front to back is dead on, within a tenth in a 10" or so circle. Left to right is more like .005", ouch. Using a known good angle plate (checked from both sides to be sure) it's clear that the spindle axis is inline with the Z axis.

So, the column or more likely the linear guides for the Z axis seem to have shifted a bit. I'm pretty sure I know what caused this and who's at fault but I can't prove anything so I'm guessing that I'm on my own here.

Is this something that can be corrected on site? How difficult is it? What are my options?

I'll be making some calls tomorrow but I wanted to get some advice in the meantime.

Thanks much for any advice.

stuart

you say that in the x axis it is out and the machine is level and you say that you checked the swuareness? you trammed an angle plate on the x and y axis an that tells you the z axis is square if that is the case then you just need to shim the spindle. put a precision pin in a collet holder and check the eunout there or indicate the taper if the z is square and the machine is level shim the spindle did you reverse the level to check calibration? if the guides shifted then you would not get good readings on the square in the x axis when you tram the head sounds like you need to shim the spindle to me or re level the machine.

I had the same problem on a cincinnati VMC, the head was cocked right to left from a crash. This machine had a carrier that the 4 ball bushings attached to, and the head attached to the carrier. I pulled the alignment taper pins and shifted the head until it indicated correctly. Cincinnati service told me to do it that way.

Despite what many people say, getting the machine level is not important. Leveling the machine is ONLY your starting point.

Before I go further, has the machine been dropped or crashed? If so, IGNORE the rest of what I write.
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The machine is built on a precision surface. Your floor is not a precision surface, so the machine base flexes causing the table to not be perpendicular to the spindle. First, level the machine as a starting point, then adjust the leveling pads to tram the table to the spindle. This, in essence, is "flexing" the machine base to how it was assembled in the factory. If the table isn't level, then so what? If you ignore this technique and decide to shim your spindle to achieve spindle perpendicularity to the table, then your x and y position will shift as you move up and down in z.

fpworks:
i agree with you completely. there is definitely enough flex in the base of the machine to influence geometry. unfortunately the misalignment i'm seeing is a result of the machine being 'roughly handled' by riggers.

.005" out of tram over 10" is not possible to correct by tweaking the leveling pads!

shimming the spindle could restore the spindle's perpendicularity with the X axis but the problem is that the Z axis is not perpendicular to the X axis. i would need to shim the column to get things back in order but that doesn't appear to be possible without major disassembly of the machine.

thanks for the replies so far.

sheys said:

Front to back is dead on, within a tenth in a 10" or so circle. Left to right is more like .005", ouch. Using a known good angle plate (checked from both sides to be sure) it's clear that the spindle axis is inline with the Z axis.

Click to expand...

When you put the indicator in the spindle and run it up and down the angle plate, with the angle plate in line with the Y axis, does the indicator move .005 in 10"? Or does the indicator stay zeroed? If is stays zeroed, the axis is square to the table and the spindle is not parallel to the axis. If it moves, the axis is not square. It's also possible that both have been bumped out of position.

What brand machine is this, and how big is it?

Mudflap said:

When you put the indicator in the spindle and run it up and down the angle plate, with the angle plate in line with the Y axis, does the indicator move .005 in 10"? Or does the indicator stay zeroed? If is stays zeroed, the axis is square to the table and the spindle is not parallel to the axis. If it moves, the axis is not square. It's also possible that both have been bumped out of position.

Click to expand...

The indicator moves .0025 over a few inches (cant recall the distance exactly, it was as far as i could reach with the setup i was using) on the angle plate in line with Y. Flip the plate 180 degrees, trace the same path and it reads -.0025 over the same distance. So, plate is fine (otherwise it would be positive in both directions).

With the angle plate in line with the X axis things are fine (no reading).

This is a Milltronics VM16. 30x16, 9000lbs.

If it was here, I'd start jacking the leveling pads like fpworks described. That's not the most rigid machine in the world, I can move my 20K lbs cincinnatis that much if I lose track of where I started. Just because the table is level doesn't necessarily mean that the base of the machine is completely level. Also If it was stored for a while during the move without being leveled it may have taken a set and needs to relax back to it's original shape. Did you run the table to the 4 extremes of it's travel and check it for level there?


Is the column cast in one piece with the bed?

Mudflap said:

Is the column cast in one piece with the bed?

Click to expand...

Column is bolted to the bed though the bolts are essentially impossible to get to.

The machine has been sitting in a few different places over the past month so who knows what may have happened.

I'll give the leveling feet a much more thorough messing with tomorrow. I wouldn't have thought that much misalignment could be a result of twist in the machine but hell, what do I know. Man would it be great if that's all it is!

Thanks a lot guys.

I've brought many Milltronics Z axis back to straight/square. This isn't that bad of a job but it takes patience and the proper equipment. I've done them in as little as 2 hours and as long as all day, depends on luck and skill.

I'm betting that the ways are not square and also not straight. If you're looking to fix them yourself I would suggest a tall granite square to start with. It can be a real b**** to get them straight using only a short square.

The rails need to be loosened, realigned and carefully tightened. All the while checking your progress with a square. Straightness, squareness and tram all have to be accounted for.

Dan

C-frame machines have an order to be checked/adjusted so the last adjustment won't affect the next.
start at the table and work your way through the machine via the x-rails, y-rails, column, z-rails, then spindle cartridge.
1 table flatness in x&y (re-grind if not flat).
2 parallelism of x-travel to table surface (grind shims on the x-axis rail trucks to correct).
3 parallelism of y-travel to table surface (grind shims on the y-axis rail trucks to correct).
4 x-y axis squareness (adjust with the y-axis rail trucks to correct).
5 squareness of column to table surface in x&y axes (lift the column and scrape the mounting if the levelling feet can't be used to correct).
6 check the parallelism of the spindle to the z-axis in the x&y planes. This is where I think your error is. You could shim or scrape the spindle cartridge square again or loosen all the screws holding the z-axis rail trucks then check the clamps that keep them held against the fixed faces on the sides are tight. Re-tighten the truck screws and check again. If it is still out, a little shim between the truck and the fixed face at one end should correct it (make sure all the truck screws are loose before shimming and loosen the screws on the ballnut and re-tighten after shimming to guarantee the screw will still be central).

thanks everybody-

i pulled the cover off the head to get a look at the Z axis rails. seems that this is likely where the error is. i can see how they could be adjusted if necessary.

what a pain; though it is interesting to see how the machine is actually put together. at least i'm learning something.

I have actually adjusted a machine via the rails before... after a crash. It is a PITA, but doable. basically you loosen the rails & their should be adjusting screws along side one of them. It takes a bit of experiementing to get it right....first you gotta check the table. Then you need to check off the table...at least 12"...the checks for any twist you might get. Plan on a full day to do this & another day to put all the guards back on.