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G2, G3 - Controlled Arc Move

1.0.0-beta planner Add an arc movement to the planner

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

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).

G2 X125 Y32 I10.5 J10.5 

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).

G3 X125 Y32 I10.5 J10.5 

Move in a complete clockwise circle with the center offset from the current position by [20, 20].

G2 I20 J20