[Marlin] G002-G003 - Arc or Circle Move

📅Update: 2020/09/18
Description
G2 adds a clockwise arc move to the planner; G3 adds a counter-clockwise arc. An arc move starts at the current position and ends at the given XYZ, pivoting around a center-point offset given by I and J or R.
​CNC_WORKSPACE_PLANES allows G2/G3 to operate in the selected XY, ZX, or YZ workspace plane.
This command has two forms:
I J Form
I specifies an X offset. J specifies a Y offset.
At least one of the I J parameters is required.
X and Y can be omitted to do a complete circle.
The given X Y is not error-checked.
The arc ends based on the angle of the destination.
Mixing I or J with R will throw an error.
R Form
R specifies the radius. X or Y is required.
Omitting both X and Y will throw an error.
X or Y must differ from the current XY position.
Mixing R with I or J will throw an error.
Arc moves actually generate several short straight-line moves, the length of which are determined by the configuration option MM_PER_ARC_SEGMENT (default 1mm). Any change in the Z position is linearly interpolated over the whole arc.
'ARC_P_CIRCLES' enables the use of the 'P' parameter to specify complete circles
Usage
G2 [E<pos>] I<offset> J<offset> [P<rate>] R<radius> [X<pos>] [Y<pos>] [Z<pos>]
Parameters
[E<pos>] The amount to extrude between the start point and end point
I<offset> An offset from the current X position to use as the arc center
J<offset> An offset from the current Y position to use as the arc center
[P<rate>] Specify complete circles - requires ARC_P_CIRCLES
R<radius> A radius from the current XY position to use as the arc center
[X<pos>] A coordinate on the X axis
[Y<pos>] A coordinate on the Y axis
[Z<pos>] A coordinate on the Z axis
Gallery
G3 command geometry
This illustrates a counter clockwise arc, starting at [9, 6]. It can be generated either by G3 X2 Y7 I-4 J-3 or G3 X2 Y7 R5
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examples:
Move in a clockwise arc from the current position to [125, 32] with the center offset from the current position by (10.5, 10.5).
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G2 X125 Y32 I10.5 J10.5
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Move in a counter-clockwise arc from the current position to [125, 32] with the center offset from the current position by (10.5, 10.5).
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G3 X125 Y32 I10.5 J10.5
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Move in a complete clockwise circle with the center offset from the current position by [20, 20].
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code: G2 I20 J20
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