CNC drilling commands
•manually create, edit, save and run a CNC program;
•create a CNC program by using CAM software;
•manually edit a CNC program initially created by CAM software.
Chapter 3 explained how to use commands typed in MDI mode to drill holes at specific locations by following a simple, logical process:
•type modal commands to set the units (millimetres or inches) and various
other settings that will apply to all subsequent commands;
•type commands to move to specific positions;
•at each position, drill a hole.
That all works well, but it is rather tedious to have to do that each time we want a particular set of moves. It is also prone to error as we follow a written list of coordi- nates and type the relevant commands. Instead of using MDI mode, we can turn our instructions into a simple program that we can create entirely, and preview the results on screen, before running the program with a real workpiece. Saving the program will ensure it can be recalled and run again at any time.
In the CAD/CAM/CNC cycle, simple programming omits the CAD and CAM parts and deals directly with creating a set of G code commands. This is ideal for simple tasks (although simple programs can sometimes do complex tasks) and can be a quick way of producing a part. When we get to the full CAD/CAM/CNC cycle, it is essential that you understand what is happening at the CNC stage, and doing a bit of simple programming is the best way to learn. There are at least two main ways of creating a program:
•Type commands into a text file then take those into a CNC program. Some CNC programs may allow program commands to be entered directly into the program in ‘program’ mode, then saved as a text file. It amounts to the same thing.
•Use CAM software to create a program. In this case, a drawing is created in the CAM program (or a ready-made drawing, prepared using other soft- ware, is brought into the CAM program) and the CAM program creates the program instructions for the CNC program. These instructions are saved from within the CAM program, then imported into the CNC program.
One method is not better than the other; they both have their strengths and weaknesses, but an understanding of both methods is required to be able to make a good choice of method for any job. Both methods are shown below.
