Published 12/15/2009

Understanding Custom Macro Version A

Custom macro B is the more powerful and desirable version of custom macro. However, there are still control models that can be equipped with custom macro version A, so never assume that a given machine you plan to purchase will be (or can be) equipped with custom macro B.

Basics

Mike Lynch

Founder and President, CNC Concepts Inc.

One limitation of custom macro A is that you cannot use a decimal point in custom macro commands. All values must be expressed as integers. If you know the fixed format for certain CNC words, this isn’t too bad.

For example, if you’re working in the Imperial (inch) system and want to express an X word of 10.0 inches, the fixed format (with no decimal point) for most machines is X100000. Whenever performing calculations, or providing input data, you must use integers.

With custom macro B, a G65 is used to call a custom macro. This is not the case with version A in which case a G65 simply specifies that the command is custom macro. An H word specifies what kind of command is being given.

This gets a bit confusing, because every kind of arithmetic and logic command has its own H word—and unless you have all the H-word values memorized, you can’t simply scan a custom macro A program and tell what is happening. Three letter addresses—P, Q and R—are used within G65 commands to further clarify what is actually happening. Here are some examples showing the basic arithmetic functions:

Equal (H01): custom macro B: #101=1 – custom macro A: G65 H01 P#101 Q1

Add (H02): custom macro B: #101=4+1 – custom macro A: G65 H02 P#101 Q4 R1

Subtract (H03): custom macro B: #101=4-1 – custom macro A: G65 H03 P#101 Q4 R1

Multiply (H04) custom macro B: #101=4*2 – custom macro A: G65 H04 P#101 Q4 R2

Divide (H05) custom macro B: #101=4/2 – custom macro A: G65 H05 P#101 Q4 R2

Note that only one arithmetic operation can be performed per command, meaning some expressions must be divided into multiple commands. Consider the following command given in custom macro B format:

#101 = 6 * [4+5]

This requires two commands in custom macro A:

G65 H02 P#101 Q4 R5 (Add four to five)

G65 H04 P#102 Q6 R#101 (Multiply 6 times 9)

Custom macro A programs are tedious to write and interpret. I always recommend writing the custom macro in version B first, then converting it to version A.

Here is a more complete example. This custom macro will machine a bolt pattern of holes. First let’s look at the main (calling) program:

O0008 (Main program)

N005 G54 G90 S800 M03 T02 (Select coordinate system, absolute mode, start spindle, get next tool ready)

N010 G00 X3.0 Y2.5 (Rapid to center of bolt hole pattern)

N015 G43 H01 Z.1 (Instate tool length compensation, rapid up to workpiece)

(Set input data)

G65 H01 P#121 Q30000 (X center)

G65 H01 P#122 Q25000 (Y center)

G65 H01 P#123 Q0 (Z surface)

G65 H01 P#124 Q17500 (Bolt radius)

G65 H01 P#125 Q7500 (Hole depth)

G65 H01 P#126 Q45 (Starting angle)