calibration still off? Parts not right size.

[slinky7]

I calibrated all my x axis and based on my measurement I am .0003 off when moving 1" on my dial indicator. When I move
my X axis say 20" I am off about 1/8". It seems the further the movement the worse it gets. I do not understand why this is
and how can I fix it. I have let mach calibrate my X axis as best I can but still can't get any better the .0003 when moving 1".

My cnc machine is made of 8020 with 2 - 5 start 10 TPI acme screws and has two leadnuts with anti backlass if this helps.


-Dennis

[Hood]

How accurate is the acme?
How accurate is your measuring when letting Mach calibrate?
Hood

[slinky7]

When I calibrate in the settings tab I let mach move the axis say 1" then it sets the calibrated value. Then I
re-zero my machine reset my dial indicator and then verify the setting by moving
the x axis in the MDI box X1.0 and see what the dial indicator reads.
My screws are precision acme rods from McMasterCar.

[ger21]

Do the calibration over a larger distance, like 6".

Or just calculate the correct steps per inch and enter that number. For 1/10 microstepping, enter 4000 steps/unit.