Relation between compensation files and backlash

 
Hi guys. I am currently struggling with linear positioning errors in cnc. According to my researchs, i've discovered compensation file usage in linuxcnc. I've experienced how to use it and i think i've understand how it works, but there is a little issue, i didn't understand how to use this comp files with backlash. In LinuxCNC documentation about writing compensation files, it is mentioned as:

"If COMP_FILE is specified for an joint, BACKLASH is not used. A COMP_FILE_TYPE must be specified for each COMP_FILE."

I am trying to understand this, if backlash is ignored when i use the comp file, how can i fix backlash while fixing positioning errors at the same time? How do i measure linear positioning errors with backlash and combine them in single comp file? What is the methodology?

Thank you for your answers.

 

If you use a Type 1 comp file then the backlash is built-in to the numbers in the file.
This also means that the backlash can vary through the travel, so can compensat for screws that are more worn in some areas than in others.

If you have 0.1mm backlash then the file might look like

0 ,-0.05, +0.05
10, 9.95, 10.05
20, 19.95, 20.05

And so on.

Thank you for your answer @andypugh. I think i solved this problem. I've recently opened a new topic, if you have knowledge about that, can you give an answer?
Here is my new topic: forum.linuxcnc.org/38-general-linuxcnc-q...1-compensation-files