Arc Tolerance

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10 Aug 2015 03:34 - 10 Aug 2015 03:35 #61255 by BigJohnT
Replied by BigJohnT on topic Arc Tolerance
It is in the 2.7 docs Getting Started Guide.

www.linuxcnc.org/docs/2.7/html/getting-s...dating-linuxcnc.html

JT
Last edit: 10 Aug 2015 03:35 by BigJohnT.
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22 Jul 2016 00:24 #77802 by GM2012
Replied by GM2012 on topic Arc Tolerance
I've just converted my Sherline lathe to CNC and my second test ngc already gave me this "Arc radius to small to reach end point". It is all about arc accuracy and I do not see where the error in g-code is. I've drafted cutting line in CAD with 0.0000 tolerance in mm and all looks good.
Anyhow ... as I've found this thread I've finally upgraded my old Ubuntu which was running with no upgrades for few years. As explained in this thread, patch to fix the tolerance issue is added in axis 2.7 and I am running fresh installation of 2.7.5. As soon as I've started Axis and opened the same ngc file I've got the same error.
As I am just Linux user and have no much in depth knowledge I am not eve sure where this 'patch' is located as I wanted to see what is the tolerance now.
My lathe is metric lathe. G-code generated defines arc with X Z R, not X Z I K, for example. It is SolidCAM and I even couldn't find a way that I get 'typical' arc with X Z I K

G2 X5.575 Z-14.808 R1.027

I was using custom built CNC machine for few year and EMC but never encountered an issue with arc tolerance.

Any input here is appreciated.

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22 Jul 2016 03:10 - 22 Jul 2016 03:12 #77803 by GM2012
Replied by GM2012 on topic Arc Tolerance
It looks like I found the 'problem'. It was the difference in having G7 and G8 mode.

As G-Code generated had to be modified I've made a mistake by adding line

G18 G7

And later

G18 G8

So second line was 'extra' and I've deleted it. GCode loaded fine after this change. :silly:
Last edit: 22 Jul 2016 03:12 by GM2012.

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09 Mar 2018 19:31 - 09 Mar 2018 19:34 #107169 by kpj10
Replied by kpj10 on topic Arc Tolerance
For the image uploaded can setting arc tolerance_mm value will solve my problem, or is it a G-code error?
The possibility of the latter being true is limited as I have tested my G-code on the online g-code simulator, and I can see exactly what I have drawn.

I have tried in my 2.7.0~pre7 ini configuration file, to set the value TOLERANCE_MM = 0.2, and still, I'm getting the same error.

On my laptop, I'm using the linuxcnc-mirror-reverse branch.

The code on the line is G03X-17.086Y17.698I-16.918J.66.

The distance mode is G91. Thank You.

Kunal.
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Last edit: 09 Mar 2018 19:34 by kpj10.

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12 Mar 2018 13:37 #107243 by andypugh
Replied by andypugh on topic Arc Tolerance
Can you get your CAM software to output more places of decimals?
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18 Mar 2018 16:39 #107498 by kpj10
Replied by kpj10 on topic Arc Tolerance
Yes, maybe. Trust me it is easier to get solutions here than from the cam software support. I will reply back in case I face any difficulty. Thank you.

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21 Jun 2018 07:51 #112705 by Bloumielies
Replied by Bloumielies on topic Arc Tolerance
Hi Gentlemen

Do any of you possible have a procedure to adjust the tolerances in the ini file? When I open my ini files there is no tolerances that can be set? Is this something one needs to add manually? Do any of you maybe have a sample code or procedure how to do this?

I have done the following actions to try resolve this without any luck.
1. Set post processor tolernace to 0.0000X
2. Chnage to incremental mode
3. Diasble arc fitting
4. Played with lead-in lead-out

I keep on getting the same issue.

Thank you

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23 Aug 2018 01:01 #116467 by stidrvr
Replied by stidrvr on topic Arc Tolerance
Anyone? Im still getting this error in 2.7 can someone explain in noob terms how to adjust the TOLERANCE_INCH setting?

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24 Aug 2018 10:53 - 24 Aug 2018 10:54 #116522 by andypugh
Replied by andypugh on topic Arc Tolerance
I can understand your difficulty here.

The setting is not included in the INI config docs:
linuxcnc.org/docs/2.7/html/config/ini-co...ml#_rs274ngc_section

And the setting is not called TOLERANCE_INCH either. Looking at the actual code:
github.com/LinuxCNC/linuxcnc/blob/2.7/sr...rs274ngc_pre.cc#L986
The settings need to go in the [RS274NGC] section of the INI file corresponding to your machine config and are called:
CENTER_ARC_RADIUS_TOLERANCE_MM
and
CENTER_ARC_RADIUS_TOLERANCE_INCH

These settings probably ought to be mentioned in the docs...
Last edit: 24 Aug 2018 10:54 by andypugh.

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24 Aug 2018 11:33 #116536 by BigJohnT
Replied by BigJohnT on topic Arc Tolerance
I looked in interp_internal.hh for the tolerance and found this
#define CENTER_ARC_RADIUS_TOLERANCE_INCH (2 * 0.001 * M_SQRT2)
#define CENTER_ARC_RADIUS_TOLERANCE_MM (2 * 0.01 * M_SQRT2)
but I don't know how to spell out in the docs the tolerance from those lines.
I did find the default values for arc tolerance
#define MIN_CENTER_ARC_RADIUS_TOLERANCE_INCH 0.00004
#define RADIUS_TOLERANCE_INCH 0.00005
#define MIN_CENTER_ARC_RADIUS_TOLERANCE_MM 0.001
#define RADIUS_TOLERANCE_MM (RADIUS_TOLERANCE_INCH * MM_PER_INCH)

JT

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