M98 & M99 - Subroutines

DMC File Mode: Supported

Streaming Mode: Supported

Description

M98 and M99 enable the creation and use of subroutines in G-code programs. Subroutines are reusable blocks of code that can be called multiple times, helping to reduce program size and improve maintainability for repetitive operations.

M98: Calls a subroutine by its program number
M99: Returns from a subroutine back to the main program
N-labels: Define subroutine start points using N followed by a number

Syntax

; Subroutine definition

N100 ; Start subroutine 100

G1 X10 Y10 F500 ; Subroutine commands

G1 X20 Y20

M99 ; End subroutine

; Subroutine call

M98 P100 ; Call subroutine 100

M98 P100 L3 ; Call subroutine 100, repeat 3 times

Parameters

Parameter	Description	Example
P	Program number to call (1-9999)	P100
L	Number of times to repeat (optional, default: 1)	L5

Examples

Basic Subroutine

; Define a simple drilling subroutine

N200 ; Start subroutine 200

G1 Z-5 F100 ; Drill down

G4 P500 ; Dwell 0.5 seconds

G1 Z5 F500 ; Retract

M99 ; Return from subroutine

; Main program

G0 X10 Y10 ; Position for first hole

M98 P200 ; Drill hole

G0 X20 Y20 ; Position for second hole

M98 P200 ; Drill hole

Repeated Subroutine Call

; Define a step pattern subroutine

N300 ; Start subroutine 300

G1 X5 F200 ; Move 5mm in X

G1 Y1 ; Move 1mm in Y

M99 ; Return from subroutine

; Create a staircase pattern

G0 X0 Y0 ; Start position

M98 P300 L10 ; Call step pattern 10 times

Complex Machining Sequence

; Tool change and setup subroutine

N500 ; Start subroutine 500

G0 Z25 ; Retract to safe height

M5 ; Stop spindle

G4 P2000 ; Wait for spindle stop

M3 S1200 ; Start spindle at 1200 RPM

G4 P1000 ; Wait for spindle to reach speed

M99 ; Return from subroutine

; Use in main program

M98 P500 ; Setup for operation

G1 X10 Y10 Z-2 F300 ; Begin machining

Forward Declaration - Call Before Definition

; Main program calls subroutine before it's defined

G0 X0 Y0 ; Start position

M98 P1000 ; Call subroutine 1000 (defined below)

G0 X50 Y0 ; Move to next position

M98 P1000 ; Call same subroutine again

M2 ; End program

; Subroutine defined after main program

N1000 ; Start subroutine 1000

G1 Z-3 F200 ; Plunge

G1 X10 Y10 ; Cut pattern

G1 X0 Y10

G1 X0 Y0

G1 Z3 F500 ; Retract

M99 ; Return from subroutine

Note: Subroutines can be defined anywhere in the file - before or after the M98 calls that reference them. The entire file is parsed first, so all subroutines are available regardless of their position in the file.