In the machining industry, the numerical axis plays a key role in cutting production times and lead times. It also helps reduce production costs and labour, since multi-axis machines need very little operator intervention.
What is a numerical axis?
In machining, an axis is the ability of a machine to move the cutting tool or the workpiece in one or more directions along a defined path. Every machine tool has a numerical axis; on the simplest, conventional machines these are the X, Y and Z axes, which follow the principles of a mathematical plane.
Machines with a simple numerical axis can carry out basic machining operations. Lathes, milling machines and drilling machines are examples. However, there are also machine tools with multiple numerical axes: the more axes a machine has, the greater the benefits for machining.
The numerical axis in CNC
CNC, or computer numerical control, is one of the most advanced machining methods available. It is a type of automatic work that needs very little human intervention. This is because the machine tool runs on a central computer that operates the cutting tools needed for a given job.
For the computer to know along which numerical axis to move the tool or the workpiece, the design of the part has to be loaded into it. To do this, the engineer or operator creates the design on a separate computer using specific programming software such as CAD and CAM: one designs the part, while the other turns that design into physical reality.
Once the design is ready, it is loaded into the machine tool's computer and translated into the alphanumeric CNC language that the machine uses. Through this language the computer knows which cutting tool to use on the part, how fast it must move, what the depth of cut is, and so on.
Machines with CNC can carry out several different operations on the same part in a single process. The part does not need to be repositioned or readjusted on the worktable, and the operator does not have to remove the milling cutter, for example, and fit a drill in the spindle. The machine does it by itself.
Machines with multiple numerical axes
Although more and more machine tools now include CNC, not all of them have multiple numerical axes. Only machining centres, lathes and milling machines offer this function. Do you know what the numerical axes are on these machines?
Machining centres
The machining centre is arguably one of the most advanced machine tools there is. These are highly versatile machines that can perform milling operations as well as turning, drilling and countless other machining jobs. They can mass-produce parts and make complex, small and/or very simple components.
In a machining centre the workpiece stays still while the cutting tool rotates to remove chips. But be careful: the workpiece actually makes a very simple movement together with the table so that it can be positioned or oriented relative to the tool. A machining centre has five numerical axes:
- Main axes. These are the X, Y and Z axes. They represent the longitudinal, transverse and vertical movements.
- A axis. This numerical axis positions the workpiece at a specific angle.
- B axis. It orients the workpiece by rotating it. On some machines it is called C.
- W axis. Only some machines have it, and it handles a pallet change.
What distinguishes machining centres, and multi-axis machines in general, is that the axes can work simultaneously. This is what speeds up machining.
Lathes
On non-multitasking CNC lathes, the workpiece is mounted in a chuck and rotates while the cutting tool stays still in the turret. On these lathes, the main axes (X, Y and Z) represent the movement of the tool as it removes chips.
Some lathes have additional numerical axes that coordinate the cutting tool and the workpiece to position the latter at the required machining angle. This makes it possible, for example, to turn parts with cylindrical or conical shapes. When a part is tilted on a lathe to give the tool a better approach angle, the numerical axis used is the B axis.
The numerical axis on milling machines
Milling machines, like lathes, can increase their number of axes depending on the complexity of the machine. That is why milling machines have a specific classification: three-axis, four-axis and five-axis. What do these axes refer to?
- X axis. This axis is horizontal and parallel to the surface of the workpiece. The movement is horizontal and longitudinal to the table.
- Y axis. It moves in the horizontal plane, transverse to the table.
- The Z numerical axis. This is where the milling cutter is mounted. Depending on the machine, it can take different positions. It moves vertically.
- A and B axes. These are found only on some machines and refer to the rotation and positioning capability of the workpiece, which improves the approach angle of the cutting tool.