U and W on a CNC Lathe (Incremental Programming)

Using U and W on a CNC Lathe

On a CNC machining centre incremental and absolute are modal. That means when one is active it stays active until you programme the other.

Now on a CNC Lathe it’s different. You just change your axis to U or W. You can remember this by its position in the alphabet UVW correspond to XYZ .

What this means is that you have U instead of X and W instead of Z. Oh and if you have a Y axis you can use V.

This can make programming easier if the drawing is dimensioned incrementally.

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Using U and W on a CNC Lathe

This is a nice convenient 10mm. If it was 10.312 then you would have to do the arithmetic in order to use absolute.

You can even mix incremental and absolute in the same block. Look at this example.

This is it with W

Using U and W on a CNC Lathe

Got to be honest I don’t use incremental that much in turning but I reckon this is a really good use for it.

If you have a slight taper in the part and you want to programme it out. This makes a really simple way.

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It is also much less prone to error. You can put it back to zero for the next time if you want.

Changing the X value can be dodgy.

So there you have it Using U and W on a CNC Lathe

Just one other thing.

DON’T FORGET

The U figure is a diameter not a radius.

So in the example above the diameter is increasing by .02 (U.02)

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