Custom Macros

A macro is an NC program with variables, arithmetic and branching. It has variables, arithmetic, IF and WHILE, and it can read the machine’s own state, so a program can adapt instead of assuming.

#100 = 25.4              (a variable)
G1 X[#100 * 2] F500      (arithmetic, in brackets)
IF [#100 GT 20] GOTO 90  (a decision)

The variables

Range	Are	Live
#1 … #33	local: arguments and scratch	per call, cleared on return
#34 … #99	reserved: a write is a block error	always vacant
#100 … #499	common	lost at power-down
#500 … #9999	common, retained	kept when the machine is switched off
#1000 upwards	system: the machine’s own state	see below

Local variables are per call. A macro that calls another macro gets a fresh set, and the caller’s are still there when it returns. Calls can nest several levels deep.

Vacant is not zero

A variable that has never been given a value is vacant, written #0. It is not the same as zero: it answers “was this ever set?”.

IF [#5083 EQ #0] GOTO 100   (tool 3 has never been measured)

A macro that treats vacant as zero will use an unmeasured tool length of nothing.

The retained band is shared with the cycles shipped on the machine, which keep their settings there. Check what a machine macro uses before choosing a slot. The full map is in Macro Variables.

Calling a subprogram

A section repeated at several places, such as a bolt pattern or a pocket cut at four positions, goes in a subprogram and is called with M98:

M98 P1000        (run program 1000, once)
M98 P1000 L4     (run it four times)

M99 at the end of the subprogram returns to the block after the call. M99 P120 returns to block N120 instead.

A subprogram is an ordinary program in the program list. It shares modal state with the caller: the units, plane and work offset in force at the call are still in force inside it, and anything it changes is still changed on the way back.

Calling a macro

G65 calls a macro and passes arguments. Each letter lands in a numbered local:

G65 P9100 X10. Y20. Z-5.    (call O9100 with X, Y and Z)

Inside O9100, X arrives as #24, Y as #25, Z as #26. M99 returns.

G65 is the call this control implements. G66, the modal call that repeats on every following block, is not.

Reading the machine

These are the system variables worth knowing. All are read-only from a program unless noted.

Where the machine is

Variables	Hold
#5021 … #5026	machine position, X Y Z A B C
#5041 … #5046	position in the active work coordinate system
#5061 … #5066	where the probe last triggered

Positions are published by the control. A program that tries to assign to one is rejected rather than quietly ignored.

Offsets and tools

Variables	Hold
#5081 …	tool length: geometry plus wear. See Tool & Work Offsets
#5221 …	work offset G54; each further system starts twenty later
#5500 / #5600	tool length geometry / wear
#5700 / #5800	tool radius geometry / wear
#5211 … #5216	the G92 shift
#5220	which work coordinate system is active
#5161 / #5181	the G28 and G30 reference positions

What the machine is doing

Variables	Hold
#3026	the tool in the spindle
#3901 / #3902	parts made / parts required
#1000 … #1031	one PLC signal each, 0 or 1
#1032	all thirty-two at once, as a number

The PLC signals let a program branch on what the machine senses right now; see PLC Signals in Macros.

Stopping with your own message

Assigning to #3000 raises an alarm and stops the program:

IF [#1000 EQ 1] GOTO 10
#3000 = 891 (fixture not clamped)
N10

This is how a macro refuses to run rather than cutting something wrong. The number is yours to choose and the text in brackets is what the operator reads.

Writing macros that survive

• Keep comments to plain ASCII. Accented and non-Latin characters in a comment can break the parse.
• Use #100+ for anything that must outlive the call. #1 … #33 are gone the moment the macro returns.
• Check vacancy before arithmetic. #0 in a calculation is not zero, and the result will not be what you expect.
• Do not assume a value someone else wrote is fresh. Cycles that publish results also publish which run wrote them; see the result record.

Tool length and work offsets from a macro

A macro reads it at #5081 onwards: #5081 is tool 1, #5082 is tool 2. It is not stored anywhere; it is a live view over the two real columns:

• Reading it gives you L.Geom + L.Wear, the number the control actually uses.
• Writing it sets L.Geom so that geometry plus the existing wear equals what you wrote. Your wear correction survives.
• It is vacant (#0) while a tool has never been measured, meaning neither geometry nor wear has ever been written. A macro can test for that:

IF [#5083 EQ #0] GOTO 100   (tool 3 has never been measured)

Writing a work offset

G10 L2 P_ X_ Y_ Z_ writes a work offset directly: P1 is G54, P2 is G55, and so on. P is required.

G10 L20 is refused. Work out the value and write it with L2, or use probing.

Where to go next

• Probing from a Program: G31 and the result record, the most common thing to wrap a macro around.
• PLC Signals in Macros: branching on what the PLC senses.