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TB235 Rev1 Using XY De skew
Note XY De skew is only available in CNC10 version 2 68 and later Â
XY De skew corrects for machine tools that have the X and Y axis manufactured out of square It is very useful to correct out of square
mechanicals on large format CNC routers and other machine tools The procedure is simple All you have to do is measure the
diagonals of a square that was cut on the machine Calculate the skew with a simple formula Then enter the size of the sides of
square and the measured skew into parameters P270 and P271 and the control corrects for the out of square Now cut a new square
and make a new diagonal measurements to verify your deskew correction
Use a sufficiently large L x L square and program a drill cycle with INTERCON to make dimples in a ?soft? material like Aluminum
wood or plastic at the corners of the square 2mm deep A effective point tool for dimpling can be shop made out of a broken carbide
end mill simple use a grinder to fashion the tool into the new pointed shape I'd recommend a 400mmx400mm square minimum size
for a router The Larger you go the more accurate and easily you can measure the skew
The dimples "drilled" into the material will now look like this  The spindle is not running while making the dimples
Now use a pair of calipers to measure the diagonals D1 and D2 D1 has a "/" orientation D2 has a "\" orientation Note An
inexpensive set of 24? veneer calipers were used to measure a 400mmx400mm ?square? With a little practice you can very
accurately measure center to center of the holes On large routers even a good tape measure can be used on a very large test square
to measure D1 and D2
Now calculate the skew amount and enter into P270=S Use this formula
S = square D1 square D2 / 4 0 x L
Note that S will be negative if the "square" is leaning to the left and positive if it is leaning to the right
Go to the parameters screen and set P270= S and P271=L De skew is now active Make a new dimple test square and measure D1
and D2 if it is the same you have a square D1=D2 If you are still getting a difference between D1 and D2 S has not been calculated
correctly Reset P270 and 271 to Zero Drill a new set of dimples and measure again and recalculate S Or a "homing in" method can
be used were you decrease or increase S and drill a test square and measure to see the effect in a few iterations it easy to get a
perfect square
The advantage of the dimple method is that it allows you to quickly and easily "drill" the corners of the next test square on the same
piece of material with the same setup Saving time a materials To do this simple offset your X0 or Y0 position to dimple a new test
square just offset a little from the last one to make it easy to check the effect of the latest de skew number you have entered A
magic marker comes in handy to mark the dimples as you go "S= 034" dimples set Etc Often 2 or 3 times are required to "home in"
on the exact S value that will produce a perfect square I'm sure there are other methods to achieve the same result as well And of
course the larger the square you can make and measure the better your accuracy will be
Note We are assuming that the "turns ratio" of the machine has been set correctly BEFORE setting the De skew Check the turns ratio
by simply making an accurate measurement of L If we program a 400mmx400mm square even if the machine is not square the sides
of the rhombus will still be 400mm If your measured L doesn't match your programed L Stop And set the turns ratios properly before
setting De Skew
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Document History
Rev1 Created on 2010 03 24
by #337