Lead-screw Compensation

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25 May 2018 00:59 #111099 by silden
Hi Guys,
I read the Wiki and several post how to implement/activate the lead-screw compensation, but I cloud not get it to work.

I generated the compensation file for my Z axis with the name Z.comp.
This file is in the same location as the .ini and .hal.

I added the following lines to the AXIS 2 portion of the INI.

COMP_FILE = Z.comp
COMP_FILE_TYPE = 0

I started LinuxCNC and tested the compensation with my dial gauge.
This revealed that the compensation is not active.

I believe that I am missing something in my config and unable to locate it.

Thank you in advance

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29 May 2018 13:29 #111258 by andypugh
Replied by andypugh on topic Lead-screw Compensation
You should be able to see the correction value with Halmeter (Machine -> Halmeter in the Axis GUI )
axis.N.backlash−corr
Is the pin to look at

If you are not using Axis then feel free to enquire where to find halmeter.

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07 Jun 2018 13:05 #111869 by silden
Replied by silden on topic Lead-screw Compensation
Thank you for your reply.
I have checked with the HAL Meter and the axis.2.backlash-corr is 0.

I changed the file name and reference in the INI, but it seems not to do anything.
Should I somehow activate backlash compensation in the HAL?

Thank you

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07 Jun 2018 13:15 #111872 by andypugh
Replied by andypugh on topic Lead-screw Compensation
Is the INI entry definitely in the right section of the INI?

(which version of LinuxCNC are you using?)

The file path needs to be relative to the INI file, or an absolute path.

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07 Jun 2018 13:21 #111874 by silden
Replied by silden on topic Lead-screw Compensation
I tried absolute path and relative to the INI.
The compensation file is in the same folder as the INI.

I attached my INI and compensation file for reference.

File Attachment:

File Name: 3040_CNC_7i76.ini
File Size:4 KB

File Attachment:

File Name: Z.comp
File Size:1 KB
Attachments:

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07 Jun 2018 16:06 #111892 by andypugh
Replied by andypugh on topic Lead-screw Compensation
I don't see anything obviously wrong.

Two things worth trying:

COMP_FILE=./Z.comp
(ie, explicitly state "current folder"

Add an extra LF at the end of the last line of the file.

Is there any chance that your computer is set to a locale that uses , rather than . for the decimal separator?
The following user(s) said Thank You: silden

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23 Aug 2018 10:57 #116480 by Python
Replied by Python on topic Lead-screw Compensation
Hello, I've been adding this feature to my machine because of inaccuracies in both x and y axis. And with the x axis everything works fine, but with y I have some issues. My machine setup is that x axis are traveling in positive coordinates direction, but y axis is traveling to the negative coordinates (work table). And then I write COMP_File with the negative coordinates, Linux CNC gives me an error "joint1: compensation values must increase". so The question is there a way to work around that error without changing Y axis travel to the positive side?

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23 Aug 2018 11:54 #116482 by andypugh
Replied by andypugh on topic Lead-screw Compensation
Just re-sort the comp file into an increasing sequence.

The system reads the current position then interpolates from the comp file values.
The interpolation algorithm needs the values to increase. But that has no relationship to the direction of movement of your physical axis.
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13 Mar 2019 12:32 #128510 by Python
Replied by Python on topic Lead-screw Compensation
Thank you very much, this information that you shared helped a lot at a time. Thank you very much.

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14 Mar 2019 16:25 #128594 by pl7i92
Replied by pl7i92 on topic Lead-screw Compensation
lead screws are at this time very cheep and mutch more precise as in the early mashine building years
even Trapezional are on less then 0,05 Backlash at 1meter

and a Balscrew C7 is for so cheep Money avalable to be changed if there is a leak

considder to replace the system

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