G03 problem

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20 Jan 2011 08:33 #6782 by Nick
G03 problem was created by Nick
Hi there!


I'm one of developers gcodetools - extension for Inkscape, and some of the users reported me about bad Gcode.

Error comes up at the 43th line of attached Gcode. EMC starts to cut huge arc (outer part) instead of small part of it. What can be wrong? I've checked it at the piece of paper and saw no error :dry:.

Here's the part of the Gcode. Error shows at the last line.
%
(Header)
(Generated by gcodetools from Inkscape.)
(Using default header. To add your own header create file "header" in the output dir.)
M3
(Header end.)
G21 (All units in mm)
G00 Z5.000000
G00 X67.630205 Y64.835996

....
G03 X61.419853 Y58.112817 Z-1.419551 I0.269567 J-3.261068
G03 X61.214101 Y58.075595 Z-1.319578 I0.371130 J-2.638719
G03 X61.191611 Y58.064341 Z-1.278559 I20592.241225 J-41151.968089
...

Strange thing that this error is not shown in the Axis preview and appears only during machining.


Thanks in advance :).

File Attachment:

File Name: output.ngc
File Size:9 KB
Attachments:

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20 Jan 2011 21:59 - 21 Jan 2011 11:14 #6784 by BigJohnT
Replied by BigJohnT on topic Re:G03 problem
What was I not thinking...
Last edit: 21 Jan 2011 11:14 by BigJohnT.

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21 Jan 2011 07:57 #6786 by psha
Replied by psha on topic Re:G03 problem
I think this is minial example of this bug
%
G21 (All units in mm)
G00 X61.191611 Y58.064341 Z-1.278559
G03 X61.164566 Y58.050807 Z-1.229220 I47330.301901 J-94585.894741 F400
M2
%
At least i get similar bug
I guess it's somehow related to floating point errors - requested arc length (~10^-2) is very small compared to radius (~10^5).

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21 Jan 2011 09:58 #6787 by psha
Replied by psha on topic Re:G03 problem
Micges pointed me to interp_internals.hh file where is living constant for comparision
git.linuxcnc.org/gitweb?p=emc2.git;a=blo...b7d2a318;hb=HEAD#l50
And further tests show that if |end - start| << 10^-5 * R then it treats it as full circle.

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21 Jan 2011 12:43 - 21 Jan 2011 12:46 #6795 by Nick
Replied by Nick on topic Re:G03 problem
Thanks a lot for the answer!

I'll fix that in Gcodetools. I have thought that such small arcs are unreasonable but have no reason to replace them by straight lines. Now I have one :).
Last edit: 21 Jan 2011 12:46 by Nick.

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21 Jan 2011 12:47 - 21 Jan 2011 12:49 #6796 by psha
Replied by psha on topic Re:G03 problem
Yes, I think it's best solution :)
[offtopic]
May you catch me in IRC or drop me a mail (shramov dog mexmat dot net)? I've not found your address...
Last edit: 21 Jan 2011 12:49 by psha.

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