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Leadscrew Compensation

An-110, Copyright © by Gil Hagiz
Last updated Oct-03-2005
For version 6.01

General

Version 6 uses a new leadscrew compensation file format.
In earlier versions, the data received from the laser calibration was interpolated by the program SETCORR.EXE and was converted to a longer file named LEADCORR.n, where n was the axis number.
In Version 6 the data from the laser is entered via a data entry utility LEAD.CNC that creates short file named LEADCORR.0n.
NCPlus dynamically interpolates the comp files for every mm of motion.

Upgrade

LEAD6.EXE converts old leadscrew compensation file to the format used by version 6.
The new comp files have the name LEADCORR.0n.
The program generates the comp file and a text file image, LEADCORR.0nT.
Run the LEAD6 program from the directory where your old comp files reside followed by the directory where you want the new ones to reside:

C:\RR-OLD>
LEAD6 c:\rr\cnx

Select the axis number.
The program now lets you specify the span, which is the distance between the calibration points. Select the desired span. 48 mm is recommended. By pressing the Up-Down-Arrow keys you can select other spans.
Note: The span selection is a multiple of the original span; however, for a new laser calibration the span can be any whole number of mm, e.g., 25, 50, 100.
The program checks whether the original file has zero comp at the machine zero.
If the machine-zero is not in the table (unlikely) it tells that it is unknown.
If the machine-zero is known but the comp is not zero you have the option of leaving it as it was or rebuilding the table correctly.

Once done the the new files with their full path are displayed.
The text file LEADCORR.0nT should be verified to ensure correct conversion.
Note that the data is in encoder counts; if ballscrew with different pitch and/or encoder with different count are used the old file is useless and laser calibration should be redone.

LEAD-CAL.CNC

This utility is intended for measurement and testing of the leadscrew with a laser.
As you begin a menu lets you select between Calibration and Testing; the only difference is that the compensation is either off or on.
After that the main window opens and you have to enter:

Axis number
Span in mm
Delay after each move for the laser to record the actual position.

The program reads the limits from the CNX file and calculates the positive and negative limits as multiples of the span.
After that the rest of the steps are displayed in blue on white. The completed steps are displayed in white on blue and the pending step is blinking.

Press CS to go to the machine zero.
When the machine zero is reached the laser should be set to position zero.
Now the axis is sent to its starting point (most negative).
The last step begins the sequence of moving the span, wait the delay and continue until the most positive limit is reached.

LEAD.CNC

This utility is a data entry program that enables the user to enter the leadscrew compensation data.
The opening screen requests the axis number and whether the error is in microns or tenths.
If a compensation file for that axis exists it opens in a new window and can be edited.
If such a file does not exist a new window opens and enables the operator to enter most negative, most positive and the span, after that the positions are displayed with zero compensation.
The compensation is the programmed position minus actual position.
For example, if for programmed position of -200 mm the laser shows -200.027 the compensation should be 27 micron.

At any time you can press Esc to end.
The program then asks whether you want to save the file.
If you answer Yes the old file is renamed to leadcorr.bak and the data is saved to the axis you selected.
If you answer No the data is saved to the file leadcorr.bak, so in case of oops... the data is still saved.
Note that if you modify an existing file it is not modified unless you answer Yes.