LinuxCNC G38.3 Straight Probe Toward Workpiece

G38.3 is a LinuxCNC G-code for a straight probing move toward the workpiece. The controlled point moves in a straight line at the current feed rate toward the programmed point and stops when the probe input changes to the touched state or the programmed point is reached, whichever occurs first. Unlike G38.2, it does not signal an error if the probe is not tripped before the destination.

Source checked6/6 values · 2026-10-26

Specification

1 source

Language	gcode
Code	G38.3
Group	Probing
Syntax	G38.n axes
Dialect	LinuxCNC

Parameters

Name	Data type	Description
axes	axis words	One or more axis words define the destination point; axis words are optional except at least one must be used.

Study notes

In the G38.n table, G38.3 has target state Touched, move orientation Toward piece, and Error Signal No.
The probe input signal must be connected to motion.probe-input in a .hal file; TRUE means probe contact closed (touching), FALSE means probe contact open.
After successful probing, parameters #5061 to #5069 are set to the X, Y, Z, A, B, C, U, V, W coordinates of the controlled point when the probe changed state, in the current work coordinate system.
After unsuccessful probing, #5061 to #5069 are set to the coordinates of the programmed point; parameter 5070 is set to 1 if the probe succeeded and 0 if it failed.
The tool in the spindle must be a probe or must contact a probe switch.
It is an error if the current point equals the programmed point, no axis word is used, cutter compensation is enabled, the feed rate is zero, or the probe is already in the target state.
(PROBEOPEN filename.txt) opens a file to store the 9-number coordinate of each successful straight probe; close it with (PROBECLOSE).
G38.3 moves at the current feed rate; in inverse time feed mode, the feed rate makes the whole motion take the specified time.

Safety

Cutter compensation must not be enabled during a G38.3 probe move.
A zero feed rate is an error for G38.3.
The probe must not already be in the target state when G38.3 is executed.