There are two ways to program numerically controlled machines. One is the ISO method and the other is CNC conversational programming. While ISO programming is geared towards series production, conversational programming focuses on small batches or one-off parts. The conversational method stands out where the parts to be produced call for flexible, agile programming.
The keys to conversational programming
CNC conversational programming first appeared at MIT in Massachusetts, United States. At the time, researchers managed to automate a large milling machine using a computer to control it. A curious fact from that period is that the computer used to automate a machine tool for the first time was much larger than the milling machine itself.
Fortunately, computers have evolved over the years and become ever smaller and easier to use. Thanks to this, CNC has spread to a wide range of machine tools, bringing great benefits to the metalworking industry.
What is CNC?
CNC, or computer numerical control, refers to a technology fitted to certain machine tools that allows a computer to control the position and speed of the machine. Thanks to numerical control, the machine can perform movements and operations that would be much more difficult, expensive and sometimes impossible to carry out manually.
A CNC machine can, for example, move a tool along three axes at the same time to execute specific patterns preloaded in the machine. The computer controls the machine, so one of the great benefits of this system is that an operator is not needed at all times. That is why using a CNC machine brings lower production costs, less labour and better waste management.
But why is it called numerical control? Because, for the computer to carry out the series of tasks needed for a specific job, it has to be programmed using numerical codes. As mentioned above, this can be done in ISO or conversational programming. The computer receives the instructions for what is to be done and follows a logical pattern or sequence that is translated, in turn, into commands for the machine tool.
How does CNC conversational programming work?
CNC conversational programming is much easier to use today than a few decades ago, when the procedure was manual. Today, the operator selects the operation the machine is to perform, and the machine itself asks for all the data and fields it needs before starting the job. This makes programming much simpler and faster.
Another, even easier way to program is using CAD/CAM software. CAD is used to create designs on a computer, and the design is then translated into a series of commands by CAM software. So the conversational program (or instructions for the computer) can either be entered manually by the operator, by carrying out a series of calculations and operations, or generated automatically using software such as CAD and CAM.
Machines use a specific language in order to operate, i.e. a set of data to process in order to perform a series of tasks; to carry out machining operations, machines need special commands. The set of data, information or commands that correspond to the same stage of the machining process is called a block or sequence. These commands are interpreted by the machine itself using specialised software and, to be processed, they must include the geometric, machine and technological functions of the machining operation.
CNC programming codes
In the world of metalworking, DIN standards govern much of the industry’s activity, and conversational programming is no exception. The main codes used in CNC come from standards 66024 and 66025.
These codes include the letter N, which refers to the address corresponding to a sequence or block number. N is the main command and is followed by a numerical code of three to four digits, with a maximum of 1,000 programmable blocks; the numerical range therefore runs from N000 to N999. CNC conversational programming also uses the letters X, Y and Z to set the addresses for dimensions along the X, Y and Z axes of the machine tool. The letter G is also used; it is the address for preparatory functions. In machining, these indicate the shape of the path the tool must follow, automatic cycles, programming, tool compensation and so on. The letter G is followed by a two-digit numerical code and up to 100 functions can be programmed: from G00 to G99.