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5 The Coordinate Data
38
Fig. 5.1-1
5 The Coordinate Data
5.1 Absolute and Incremental Programming (G90, G91), Operator I
The input coordinate data can be specified as absolute or incremental values. In an absolute
specification, the coordinates of the end point have to be specified for the control, for an incremental
data, it is the distance to go in the block.
G90: Programming of absolute data
G91: Programming of incremental data
G90 and G91 are modal functions. Parameter CODES will decide which state will be assumed by
the control system at the time of power-on.
Movement to an absolute position is only feasible after a reference point return.
Example:
As shown in the Figure, a movement can be
programmed in one of two different ways.
G90 G01 X20 Y50
G91 G01 X-40 Y30
Operator I will be effective under the conditions of an
absolute data specification. It is only applicable to the
coordinate, whose address precedes it. It means an
incremental data. The alternative way of solving the
above example:
(G90) G01 XI-40 YI30
G01 X20 YI30
G01 XI-40 Y50
5.2 Polar Coordinates Data Command (G15, G16)
Alternatively, the coordinates of the end point can be entered with polar coordinate data
specification, i.e., with the specification of angle and radius.
G16: Polar coordinate data command
G15: Polar coordinate data command cancel
The control is in G15 state after power on. G15 and G16 are modal functions.
The data of polar coordinates are effective in the plane defined by G17, G18, G19. When a data is
specified, the addresses of the plane's horizontal and vertical axes are regarded as radius and angle,
respectively. For example, in G17 sate, the data written at addresses X(U) and Y(V) are the radius
and angle, respectively. CAUTION! In state G18, Z and X are the horizontal and the vertical axes
(data of R and angle, respectively).
When an angular data is specified, the positive and the negative directions of the angle are counter-
clockwise and clockwise, respectively.
The data of the rest of axes will be assumed to be Cartesian coordinate data. The radius and the
angle can be specified both as absolute and as incremental data.
When the radius is specified as an absolute data, the origin of the current coordinate system will be
the origin of the polar coordinate system: