09-11-2012, 04:42 PM
Part Programming Commands
21-CNC COMMAND.pdf (Size: 237.74 KB / Downloads: 148)
Part Program Headers
The M48 header is used to give your machine general information about the job. This includes the size of tools you want to
drill and/or rout the PC board, the kind of measurement system you are using, the direction of the X and Y axis of the work,
and other details. These instructions may be generally listed in any order in the header. The part program header is
optional. Most commands that you can program into the header can also be entered at the CNC-7 console before the
program runs.
Part Program Body
The set of drilling and/or routing commands is called the part program body. It is usually much longer than the header and
tells the machine exactly where each hole is to be drilled, which drill bit to use, what shape you want routed, etc. The
commands are laid out in the sequence you want them carried out on the PC board. For example, one line of the program
will tell the machine where to drill a hole, the next line will tell where to drill the next hole, the next line will tell the machine
to stop and change the drill bit. Usually the program is carried out in sequence from top to bottom. However, some
commands will tell the machine to move to another location on the PC board, go back to a previous line in the program, and
repeat the pattern.
Excellon Program Format vs. Other Manufacturers
Because Excellon is a pioneer in the manufacture of computerized drilling and routing equipment, it was necessary for
Excellon to develop a set of commands to control the machines. The set is called Excellon Numeric Control and it uses the
same commands for all Excellon machines. Some of these commands have become standard in the industry and are widely
used by other manufacturers. The first machines introduced by Excellon were drilling machines. The set of commands used
on drillers later became known as Format One. When Excellon introduced machines with routing capability, a set of
commands called Format Two was created. Then in 1979, Excellon revised Format Two to combine drilling and routing
commands into one common set. The machines introduced prior to 1979 are called generation one machines and cannot
use Format Two. They do not have all the capabilities of the newer machines. However, newer generation two machines can
run part programs with either Format One or Format Two commands.
The Header: Setting Up The Job
The header is always located at the beginning of a part program. It consists of a series of instructions (commands) that are
used to give your machine general information about the job. This includes the size and speed of tools, the kind of
measurement system you are using, the direction of the X and Y axis of the work, and other details. The header can have
just a few commands, or dozens of them, depending on your needs. Most of these commands may be placed in any order.
But one thing the header may NOT include is machine motion commands such as JOG or HOME. Do you remember that we
said the header is optional? This does not mean that the commands you write into a header are optional. If you choose not
to use a header, then you must either write the commands into the part program or enter them at the CNC-7 console before
the program runs. Entering them manually can lead to problems. Suppose that you get an order to produce a set of the
same PC boards every two or three months. Each time the program is loaded into the CNC -7, you must be given
instructions on all the commands that have to be entered before the job can begin. If you put the commands in the header
instead, you are assured of consistent settings for the machine.