Set up
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need a high accuracy standard, such as a laser interferometer.
You can use a dial indicator to check short distances, but a laser
provides the best results. If you have to use a dial indicator, be
sure it is the highest available accuracy.
To check the accuracy of the DRO system:
1. Place the target of the laser or the needle of the dial
indicator directly on the Newall reader head.
It is absolutely critical that you take the readings directly
from the Newall reader head.
If you have to use a dial indicator, be sure that the needle of
the indicator is perpendicular to the reader head and not
angled.
If you take readings anywhere else on the machine,
machine errors may distort the results.
2. When the reader head moves, the movement registers on
the laser / indicator and DRO display.
3. Set the laser / dial indicator and DRO display position
displays to 0.
4. Make a series of movements and compare the position
readings between the laser / dial indicator and the DRO
display.
If the readings match within the accuracy specificed, then
you know that the DRO system is operating properly. If this
is the case, you can proceed to the next step: evaluating the
machine errors. If the readings do not match, you must
repair the DRO system before proceeding with error
compensation.
To evaluate machine errors:
1. Put the laser target / dial indicator on the part of the
machine where the machining is done.
2. Make a series of movements and compare the position
readings between the laser / dial indicator and the DRO
display.
The difference between the laser / dial indicator reading
and the reading on the DRO display is your machine error.
3. Plot the machine error along the entire axis of travel to
determine the nature of the error.
If it is a linear error, you can use linear error compensation.
If the error is not linear, you should use segmented error
compensation.
There are many types of machine error, including pitch, roll,
yaw, flatness, straightness, and Abbe error. The diagrams below
demonstrate these errors.
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