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Author Topic: Table Squaring Compensation....  (Read 14096 times)

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Re: Table Squaring Compensation....
« Reply #10 on: December 28, 2009, 04:59:46 PM »
Jim,
If your X-Y slide assembly is like the one pictured, can't see yours for the shield, you might be better to shim IT true to the column as it will have a much bigger footprint than the flange on the column making it a bit less sensitive and easier.

Offline RICH

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Re: Table Squaring Compensation....
« Reply #11 on: December 28, 2009, 07:00:49 PM »
Like Ray said, find yourself / borrow a good machinist square ( accurate one and not some piece of junk ) and make some measurements. I think you can shim it and get it acceptable. If possible take it over a friends if they have some precision stuff and do it there.  Fortunately it's a small machine.

RICH
 
Re: Table Squaring Compensation....
« Reply #12 on: December 31, 2009, 04:10:25 PM »
I have shimmed it up as good as I can and it's not off nearly as much...but still off by about .003 over a 4" sweep on the X and about .002 on a 4" sweep on the Y.  Now, for some reason, the mill is now stepping over on the X axis on each program cycle.  I thought maybe the timing belt was slipping, but that doesn't appear to be it and the code is fine.  It will complete a cut and when it goes to start the same cut over at a lower depth, it's stepping over to the left and will do so everytime.  So, now I have two sets of challenges...any suggestions?

Offline Hood

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Re: Table Squaring Compensation....
« Reply #13 on: December 31, 2009, 04:16:53 PM »
Sounds like your head is off compared to the Z axis, is there any way you can rotate it?
Hood

Offline RICH

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Re: Table Squaring Compensation....
« Reply #14 on: December 31, 2009, 06:08:24 PM »
You were able to get it a whole lot better than you started off with. I think you need to just slowly modify the
shimming and you can do better. I will assume that the table is ground flat in the x and Y direction and you can check it easily if you have a straight edge ( just use a feeler gauge and see if it will go under at any point (stone the edge of a piece of .001"  shim stock or see if you can detect any light under the straight edge ) say for 6" circle under the center of the collet.
You need some reference to work to so make sure the table is ok as a reference. Now do one direction at a time
If your out in one direction over 4" by .003", then shim 1/2 of it, test and repeat,etc...get one direction correct, for example the y direction reads the same as the indicator is rotated 180 degrees. Now do the x direction. When you have them as good as you can do, then put a piece of ground rod / drill blank into the collet and check the spindle. A machinist square against the rod will quickly show you how square the spindle is to the table FOR THAT COLLET only.
You can have runout on the spindle or the collet and over say 3 or 4" you may have 1 or 2 thou.
You need to work from a known reference and then check everthing one.... step ..... at a time.

BTW, when shimming place a small piece near the bolt or edge only since a different size shim may be required at each of the four bolts in the column base.
Take your time, be patience, Have  A Happy New Year,
RICH

Offline Hood

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Re: Table Squaring Compensation....
« Reply #15 on: January 01, 2010, 10:01:08 AM »
As mentioned in my previous post I think your head is off relative to the Z and actually it is most likely it was the main cause of the error rather than the Z in relation to the table.
Heres a sketch showing what I am meaning, in the left you will see as the Z moves up and down the cutter would still be on the same path.
With you shimming  the Z to make the sweep better the head moving up and down would move the cutter path to the side each time you moved on the Z.
Hood
Re: Table Squaring Compensation....
« Reply #16 on: January 01, 2010, 10:55:03 AM »
Yup...like said in #5 and 6.
The spidnle / quill needs to be tru to the Z slide FIRST .. then tram the z assembly tru to the table.
If you have a quill, it's easy to check. Put your indicator on the quill, cycle it up and down while the indicator is on the face , then the side of the column slide. If you don't have a quill, it gets a bit tricky.
RC

Offline RICH

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Re: Table Squaring Compensation....
« Reply #17 on: January 01, 2010, 01:04:32 PM »
Yep, agree with both of ya. so here is another try at it.

If the head assembly is one piece your kind of out of luck. You would need to scrape the head way to adjust if the Z is not correct to the column ways. Not a task for most folks.

Check that when the head assembly is locked that there is not a gap between
the head face and column face as sometimes the head may have a sharp end on the V edge and it will ride up in the way and throw the Z out.  Just try see if a 1/2 thou feeler will enter bettween the faces. Step #1

Then do step #2 to #5

The problem with using an indicator is that some times they don't go back to the same point after passing a crack/ table groove.

If the set screws are long enough you can lock them after all the adjustments and if you wish, with column and base "waxed" you can epoxy in the gap for a permanent as shim.

other steps in next reply
FWIW,
RICH

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Re: Table Squaring Compensation....
« Reply #18 on: January 01, 2010, 01:05:38 PM »
other steps
Re: Table Squaring Compensation....
« Reply #19 on: January 01, 2010, 01:41:55 PM »
Also Jim,
  In your first post, the compensation referred to by the mfg might be refering to backlash comp...which is there. What Ray describes would work well if the x and y axis's arent square to each other but it is not a function already set up in Mach like the backlash comp is.
Russ