Arc begin/end radius tolerance

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Ukr-Sasha
Posts: 8
Joined: Tue Jan 23, 2018 5:39 am

Arc begin/end radius tolerance

Post by Ukr-Sasha » Sat Jul 27, 2019 10:17 am

Hi everybody.
The question is rather to the developer Tom.
Tom, please help me understand - the circular interpolation code G2 / G3 does not work.
Here is an example of my simple code:

Code: Select all

G21 G90 G17
G49 G40
F100
G0 X0 Y0
G2 X60.0000 Y10.0000 I10.0000 J0.0000
M30
And when simulating the scheduler gives an error.
Although the radius of the arc is an integer and there should be no error.
Arc accuracy settings in the picture.
I can not understand what the problem is .....
Attachments
IMG_20190726_151651.jpg
IMG_20190726_151639.jpg
IMG_20190726_151623.jpg

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TomKerekes
Posts: 512
Joined: Mon Dec 04, 2017 1:49 am

Re: Arc begin/end radius tolerance

Post by TomKerekes » Sat Jul 27, 2019 1:27 pm

Hi turbothis,

This GCode defines a circle center at 10,0 (previous XY + IJ).

To create an arc starting at 0,0 (previous XY)

Radius is therefore 10

the arc should then end at 60,10 (new XY)

This is clearly impossible!

Arc.PNG
Arc.PNG (7.62 KiB) Viewed 51 times

HTH
Regards,

Tom Kerekes
Dynomotion, Inc.

Ukr-Sasha
Posts: 8
Joined: Tue Jan 23, 2018 5:39 am

Re: Arc begin/end radius tolerance

Post by Ukr-Sasha » Sat Jul 27, 2019 5:30 pm

Yes indeed.
The starting point of the arc must be in coordinates X50 Y0.
I'm just trying to understand how this feature works.
Already read a lot of information, everything seems to be simple.
But here is the code section with the real path of the part processing.
And it does not work.
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WhatsApp Image 2019-07-26 at 09.01.33.jpeg

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TomKerekes
Posts: 512
Joined: Mon Dec 04, 2017 1:49 am

Re: Arc begin/end radius tolerance

Post by TomKerekes » Sat Jul 27, 2019 7:17 pm

Hi turbothis,

Do the math for those values. Calculate the center point and then distance to beginning and end.
Regards,

Tom Kerekes
Dynomotion, Inc.

Ukr-Sasha
Posts: 8
Joined: Tue Jan 23, 2018 5:39 am

Re: Arc begin/end radius tolerance

Post by Ukr-Sasha » Sat Jul 27, 2019 8:02 pm

I did the calculations.
The difference in the distances to the beginning and to the end of the arc is 0.000289065 mm. This is more than the accuracy of the arc in the settings 0.00000254mm.
Therefore a mistake? I understood correctly?
Need to set up a CAM system and a postprocessor?
Attachments
arc.jpg

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TomKerekes
Posts: 512
Joined: Mon Dec 04, 2017 1:49 am

Re: Arc begin/end radius tolerance

Post by TomKerekes » Sun Jul 28, 2019 4:46 pm

The GCode only specifies 3 decimal digits which means the GCode will contain round off errors up to +/-0.5um. So your error calculation of 0.289um makes sense. You should probably set the error tolerance to 1um or more. This would be:

1um = 0.001mm * (1inch/25.4mm) = 3.93e-5 inches
Regards,

Tom Kerekes
Dynomotion, Inc.

Ukr-Sasha
Posts: 8
Joined: Tue Jan 23, 2018 5:39 am

Re: Arc begin/end radius tolerance

Post by Ukr-Sasha » Sun Jul 28, 2019 5:01 pm

Thank you Tom.
I will try it.

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