CNC machining centers are incredibly sophisticated and versatile pieces of technology, allowing for machining tasks to be completed with a high degree of accuracy and precision. There are a number of common commands that can be used in a CNC machining center. These commands can be helpful for beginning CNC operators and are the foundation for more advanced programming techniques.
G00: Rapid Positioning or Positioning at Feed Rate
G00, also called rapid positioning or positioning at feed rate, is a command used to move the machine rapidly but accurately to a certain position. It is the most commonly used command and is used by the CNC machine to move the tool to its ideal starting position before beginning actual machining operations. This command can be used to motion in X,Y, Z, and A axes. Each of these can be moved individually or simultaneously during rapid positioning.
G01: Linear Interpolation
In linear interpolation, the machine is instructed to move the tool along a straight line from one point to another point. This command is paired with a feed rate so the machine knows how quickly to move along the line. This command can also be used in X,Y, Z, and A axes and each axis can be given its own feed rate. This command is useful for cutting straight lines on the machined part.
G02 and G03: Clockwise and Counterclockwise Circular Interpolation
G02 and G03 are commands that allow the machine to move around a center point while either cutting the part or just in a rapid positioning operation. In a circular interpolation command, the machine will move from one point to another point in a circular arc, either clockwise or counterclockwise. The command is typically paired with a feed rate setting, just as in a linear interpolation command, and also accepts an I, J, K coordinate for the arc center point.
G04: Dwell
G04 is a command used to tell the machine to pause for a certain amount of time. This is useful for allowing tool changes or stops for the machine operator to make adjustments. This command is used with a numerical parameter that tells the machine the number of seconds to pause.
G40, G41, G42: Cutter Compensation
G40, G41, and G42 are three commands that are used to instruct the machine to automatically compensate for the cutter offset. This allows the machine to compensate for the radius of the cutting tool, allowing the operator to cut with less setup as the machine will automatically apply the offset value that was programmed into the machine prior to beginning the cutting operation.
G54, G55, G56, G57, G58, G59: Workpiece Coordinate System Offsets
G54, G55, G56, G57, G58, and G59 are commands used to set up offsets for the various workpiece coordinate systems. These offsets tell the machine how far to move each axis when the command is given to move to a given coordinate, meaning that one part can be machined multiple times on the same machine by simply changing the offset. This is useful for quickly and easily making multiple copies of the same part.
G70, G71: Finishing and Roughing Pecking Cycles
G70 and G71 are commands used to instruct the machine to use a pecking cycle for cutting. A pecking cycle breaks the cutting process into small chunks, one after the other, allowing the machine to have a faster cutting speed as it is not trying to cut the entire part out in one motion. This technique is useful when removing large amounts of material or when a high precision cut is desired and the depth of cut must be limited.
G73 and G74: Chip Breaking Cycles
G73 and G74 are commands used to instruct the machine to perform chip breaking cycles. Chip breaking cycles allow the machine to move and cut the part in a specific way that reduces the amount of material being cut at any gven time. This is useful for avoiding tool wear and for allowing the machine to have a higher cutting speed as the tool is not spending as much time in the material.
G75 and G76: Threading Cycles
G75 and G76 are commands used to instruct the machine to perform threading cycles. Threading cycles are used when cutting threads into material and allow the machine to cut the threads at a consistent depth while also controlling the cutting speed of the machine.
Conclusion
These are just a few of the common programming commands that are used on CNC machining centers. In addition to these, there are many other commands that can be used to program more advanced operations on the machine. With that said, these commands provide a great foundation for beginning CNC operators to understand the capabilities of CNC machining centers and how to achieve desired cutting results. With the proper programming, CNC machining centers can be incredibly precise and versatile, allowing for the completion of a wide variety of machining tasks with ease.
