Arc begin/end radius tolerance

[Ukr-Sasha]

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 .....

[TomKerekes]

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 (7.62 KiB) Viewed 4496 times

HTH

[Ukr-Sasha]

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.

[TomKerekes]

Hi turbothis,

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

[Ukr-Sasha]

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?

[TomKerekes]

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

[Ukr-Sasha]

Thank you Tom.
I will try it.