Proper method to level a VMC with 6 jacking screws
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  1. #1
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    Default Proper method to level a VMC with 6 jacking screws

    I have a Yang VMC 10,000lbs with 6 jacking screws. Using a 12" precision level .0005" per div. There are 4 screws on all corners and 2 in the center under the inside of the column. Would I level with the 4 corner screws and use the 2 center to shift the vertical axis of the column forward and back? Or some other way? I can take pics if needed. Thanks, steve.

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    I've always been told to level using the 4 outside corners first, then snug up the two center screws.

    Check a couple months after the first set up, then every 6 or so months after that.

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    I would suggest starting using 3 leveler and once you get it close to level then adjust the other 3. Using the 3 point method it goes a lot faster.
    Not knowing the configuration I cant say which 3. What does the manual say? Normally the center 2 are raised last. Rich

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    Quote Originally Posted by Alloy Mcgraw View Post
    I've always been told to level using the 4 outside corners first, then snug up the two center screws.

    Check a couple months after the first set up, then every 6 or so months after that.
    This is mostly what I've been told with the center feet adjusted to square the spindle.

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    I would begin with three points. I'm assuming you have three per side, use one center screw and two outside screws on the opposite side to get it ROUGH level. Get the machine square to the world north to south and east to west. Now, everything you do beyond that point will slightly hinder that perfect Level to the world condition. Keep in mind the most important thing on leveling is how the machine components move through space, that's what makes accurate parts. After the machine is rough leveled, run the last three screws down to contact. Now place your level on the table in line with the x axis and power up the machine, run the saddle + and - and check for twist (pitch), then rotate the level in line with the Y axis and check for bow (roll) you start from the bottom of the machine and work up. Next perform the same check on the X axis, if Y was done correctly and your machine is good X should be right there. Your last check on a vertical is spindle sweep. Using an indicol and test indicator sweep the table at various points of all the travel and adjust rear bolts to tilt the column as necessary, it takes very minor adjustments to correct tram. Once completed you'll find that the degree of "level" was slightly compromised, not an issue, you want the machine to move accurately through space, that's the end goal. I'be spent many hours in training with mazak to learn some of these basics of leveling and I don't consider myself an expert on leveling yet but hopefully I've passed on some basic points that will help.
    Chris German

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    Hopefully you have hold downs on the jacking screws?

    Level the table to the world. Then you lock down the screws under the table.

    Then put and indicator in the spindle and square the column to the table.

    of course you may need to go back and tweak the screws under the table if needed.

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    +1 on the three-point method.

    And don't forget to go back and check it every day for a couple of days.

    I just leveled out a bed mill that had been sitting in storage for a few months on an uneven floor. That induced a significant twist in the casting. It took a couple of days of readjustments before it finally settled in and stayed put.

    Cheers,
    Dan.

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    Ironsmith, I think, nailed it pretty well..

    "Level" is just a nice convenient starting point that will hopefully(should) get you close to the real goal...

    A machine that is nice and square and perpendicular to itself, that will make good parts is the goal..
    Also a machine that at the far ends of its travels doesn't twist off.

    When you are done messing around with indicators and test cuts and what not, you may be slightly off level, and that's just
    fine and dandy, and generally not something you need to worry about.

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    Quote Originally Posted by ironsmith89 View Post
    I would begin with three points. I'm assuming you have three per side, use one center screw and two outside screws on the opposite side to get it ROUGH level. Get the machine square to the world north to south and east to west. Now, everything you do beyond that point will slightly hinder that perfect Level to the world condition. Keep in mind the most important thing on leveling is how the machine components move through space, that's what makes accurate parts. After the machine is rough leveled, run the last three screws down to contact. Now place your level on the table in line with the x axis and power up the machine, run the saddle + and - and check for twist (pitch), then rotate the level in line with the Y axis and check for bow (roll) you start from the bottom of the machine and work up. Next perform the same check on the X axis, if Y was done correctly and your machine is good X should be right there. Your last check on a vertical is spindle sweep. Using an indicol and test indicator sweep the table at various points of all the travel and adjust rear bolts to tilt the column as necessary, it takes very minor adjustments to correct tram. Once completed you'll find that the degree of "level" was slightly compromised, not an issue, you want the machine to move accurately through space, that's the end goal. I'be spent many hours in training with mazak to learn some of these basics of leveling and I don't consider myself an expert on leveling yet but hopefully I've passed on some basic points that will help.
    Chris German
    Chris that reads like a Professor at MIT wrote it :-) I agree completely. Also be sure the machine is setting on it's leveling plates under the screws and be sure to lock the jam nuts on the screws. I also take a shaft of cold roll and tap on the top of the screws I can reach to seat the threads and plates on the floor. I only recommend as do the manufacturers for the most part to not to use hold downs unless your in a area where there are over head cranes or rail roads outside the shop where there are a lot of vibration. Or you go nuts using 100% rapid and stop fast with heavy work on the machine. If you do that, thanks as the machine will wear out faster and you will need to get it rebuilt sooner. Rich

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    lowCountryCamo --

    I'll add these suggestions:

    1. The leveling screws really want to be clean and operate smoothly. The time and effort to remove, clean, "chase" / deburr, and lube 'em is usually well spent. When reinstalling the leveling screws, adjust the three primary screws to approximately the middle of their range, the three secondary screws don't even need to protrude from the bottom of the machine base.

    2. Center the saddle on its ways and the table on its ways before you start leveling.

    3. Put a label, tape "flag", or paint a red "R" on one end of your level, and position your level on the machine so that the label, flag, or red R is always either to the machine-right or machine-rear.

    4, After the three primary leveling screws are adjusted to your satisfaction, lower the secondary screws until they bear. I generally set a dial gage holder on the concrete next to the secondary screw, with the gage plunger bearing on the machine base, note the dial gage reading, and then lower the secondary screw until the gage needle shows the machine base flex upward a half-thousandth of an inch or less. This provides a solid starting point for tram measurements that may justify footscrew "tweaking".

    John

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    Checking for twist distortion is still necessary and settling in checking has to be done.
    At Honeywell we used those crosshatched rubber pads and they settled but suction held
    machines against moving around checking was part of Preventative Maintenance.


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