CNC | G28 Code | Automatic Reference Point Return

In this article, we describe how to use G28 command for automatic reference point return in CNC machines with all details and examples.


G28 Code Introduction

The reference point is a fixed position on a machine, to which the tool can be easily moved by the reference point return or zero return function, G28 code.

With the commands of “G28 X(U)… Z(W)… (C(H)… Y(V)…);”, the numerically controlled axes are returned to the reference point. The axes are first moved to the specified position at a rapid traverse rate and then to the reference point automatically. The axes not designated in the G28 block are not returned to the reference point.

In case incremental encoders are used, manual reference point return needs to be carried out before using G28.

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“CNC | G27 Code | Reference Point Return Check”

G28 Code Format

G28 X… Z… ;

You can add other axes to G28 line.

Reference Position

The reference position is a fixed position on a machine tool to which the tool can easily be moved by the reference position return function. For example, the reference position is used as a position at which tools are automatically changed. Due to machine configuration, it’s possible to set more than one reference point.

G28 Code Example

(G90/G91) G28 X(U) ⋅⋅⋅ Z(W) ⋅⋅⋅ (C(H) ⋅⋅⋅);

For CNC Lathe, U or W can be use for incremental. For CNC Machine Centers, G90 or G91 codes can be use to select absolute or incremental mode.

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