NCT Group 2000M, 99M manual Automatic Reference Point Return G28

8 The Reference Point

8 The Reference Point

The reference point is a distinguished position on the machine-tool, to which the control can easily return. The location of the reference point can be defined as a parameter in the coordinate system of the machine. Work coordinate system can be measured and absolute positioning can be done after reference point return. The parametric overtravel positions and the stroke check function are only effective after reference-point return.

Fig. 8-1

8.1 Automatic Reference Point Return (G28)

The instruction G28 v

will return the axes defined by vector v to the reference point. The movements consist of two parts. First it will move with linear interpolation in rapid traverse to the intermediate coordinates defined by vector v. The specified coordinates may be absolute or incremental values. The movement is performed invariably in the current coordinate system .

When the end point of linear movement is reached, the cutter compensation vector is deleted. The coordinates of the intermediate point will be stored for axes defined by vector v.

In the second stage it will move from the intermediate point to the reference-point simultaneously in each axis defined by vector v. The reference-point return is carried out by non-linear movement at a speed defined for each axis. Afterwards, similar to the manual return, the position will be assumed in the manner defined by parameters.

This is a non-modal code.

LNotes:

–Unless there is a valid reference point, incremental values must be assigned to intermediate coordinates v in command G28.

–Programmed in block G28, intermediate coordinates v will be stored until power-off. In other words, the intermediate value defined in a previous command G28 will continue to be effect for the coordinates that have not been assigned values in the instantaneous (current) command G28. For example:

G28 X100 intermediate point: X=100, Y=0

G28 Y200 intermediate point: X=100, Y=200

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