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Author Topic: Table Squaring Compensation....  (Read 14095 times)

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bigjim

• 6
Table Squaring Compensation....
« on: December 25, 2009, 06:36:20 PM »
I have a Town Labs CNC mill and it has no features to square any part of the mill and it's off by quite a bit. The mill's manual speaks of some kind of compensation settings inside Mach3 to remedy this...I can't find those setting options...does anybody have any clue what to do in Mach3 to do this??

JD

HimyKabibble

• 1,687
Re: Table Squaring Compensation....
« Reply #1 on: December 25, 2009, 07:07:03 PM »
You can define formulas (in Function Configs->Formulas) to modify how Mach3 moves.  But you're FAR better off actually fixing the machine if you can.

For example, if your Y axis is tilted to the right by 0.003"/inch, you could enter a formula like this:

X = X - (Y * 0.003)
Y = Y

On a "straight" machine, when you tell Mach3 to move from Y0.000 to Y1.000, Y will move 1.000", and X will not move at all.  On this hypothetical crooked machine, that same move will cause Y to move 1.000", but X will also move to the right, off-true, by 0.003", due to the error in the machine.  Entering the above formula un-does this error.  So, now when you command a move from Y0.000 to Y1.000, Mach will actually do a two-axis move, from X0.000, Y0.000 to X-0.003, Y1.000, "un-doing" the error in the machine.

Regards,
Ray L.
Regards,
Ray L.

bigjim

• 6
Re: Table Squaring Compensation....
« Reply #2 on: December 28, 2009, 11:49:47 AM »

It's odd, when I do a sweep of the table...it's off by .026 over a 3" sweep front to back on the Y axis and .042 over 3" on a side to side x axis sweep...the table is way off.  I thought just bolting a piece of aluminum to the table and milling it flat would give me a surface to work with, but it too is off in the same way.  So, I'm not sure what's going on.  There are no adjustments on mill for anything to fix this...so, I'm hoping to figure out what I can do in Mach3 to fix this....any suggestions?

Hood

• 25,856
• Carnoustie, Scotland
Re: Table Squaring Compensation....
« Reply #3 on: December 28, 2009, 12:06:57 PM »
Are you meaning it is off on the table surface when you sweep with a dial in the Z axis? If so you need to tram the head if there is adjustment for that. If there is no adjustment then you may have to try and make some but without knowing what your mill is like its hard to say if that would be easy or not.
Hood

bigjim

• 6
Re: Table Squaring Compensation....
« Reply #4 on: December 28, 2009, 12:14:27 PM »
The table surface is off when I do the sweep with the z axis.  The mill is a 512 Town Labs model.  It basically is a Harbor Freight Mini mill head/column bolted to an iron cross slide table...and has no adjustments at all.  I can post an picture of it or even do a quick video post on youtube to show you the sweep and the mill if that would help....

• 4,902
Re: Table Squaring Compensation....
« Reply #5 on: December 28, 2009, 12:30:20 PM »
Looks lie it will take some delicate shimming or re-machining of some of the components.
The spindle centerline might be angled to the z ways too which would cause it to tram out of wack.
Is this it ?

Hood

• 25,856
• Carnoustie, Scotland
Re: Table Squaring Compensation....
« Reply #6 on: December 28, 2009, 12:31:56 PM »
First thing to find out is if its the head  that is out of square or the Z axis or both.
Hood

bigjim

• 6
Re: Table Squaring Compensation....
« Reply #7 on: December 28, 2009, 04:24:33 PM »
My model is the previous generation and is different than the current Town Labs model.  Here is a video of what my problem looks like:

tell me what you guys think??

Thanks!

Hood

• 25,856
• Carnoustie, Scotland
Re: Table Squaring Compensation....
« Reply #8 on: December 28, 2009, 04:36:12 PM »
Assuming that the actual spindle is square to the column then it looks like you are going to have to loosen these two bolts and shim to get the column true.
If the spindle is also out of square to the column then you will have to true that as well if you can, not sure how it attaches.
Hood

HimyKabibble

• 1,687
Re: Table Squaring Compensation....
« Reply #9 on: December 28, 2009, 04:37:41 PM »
First, you have to get the column perpendicular to both X and Y, probably by shimming where the column bolts to the base.  You'll need a *good* machinists square or large right angle block to check this.  This will ensure the head moves straight up and down, and doesn't move along X or Y when you change the head height.  Next, you need to get the spindle parallel to the column, in both X and Y, by shimming where the front part of the head bolts to the dovetail part.  If X and Y are not perpendicular to each other, you may be kinda screwed there, since the only fix would be re-machining the X/Y dovetails.

Regards,
Ray L.
Regards,
Ray L.