CNC

Abbreviation for 'Computerized numerical control'

History

The CNC has it´s origins in the NC (numerical control). Unlike this the CNC has an integrated computer with program memory, which can read programs, collect actual position data and control axis positions.

CNC machines are in use since 1968 (Shoda NC-111A) in the wood processing. But only since the introduction of workshop-oriented programming in the late 1980s they became more popular.

The first CNC machine was a CNC router with cross table. This machine was the first step to the later CNC-machining centre which today is the common type of CNC controlled woodworking machine.

CNC controls can be found in:

  • CNC routers and CNC machining centers
  • CNC lathes
  • CNC drilling machines
  • Panel sizing beamsaws
  • edgebanders
  • wide belt sanders
  • Most kinds of woodworking machinery can be found with a CNC controller on the market today, for many types of machines (e.g. sliding table saw, spindle router) this is limited to the top-of-the-range machines, while the standard does not have such a control.

Distinction based on the types of control

  • Point-to-Point control (PTP): Here the axes move independently of each other from an actual position (starting point) to a target position. The control in this case has no influence on the type and path of movement. This type of control commonly is used at stationary CNC drilling machines.
  • Line control: Each of the axes can be controlled in it´s way of movement. However, there is no interpolation possible between the axes. This type of control mainly can be found at edgebanders (and another through-feed machines) for controlling the exact set-in times of the units. At CNC machining centres a line control can be found at positioning axes.
  • Path control: Here are the axes interpolated with each other, so any paths within the range of axes are possible.

Distinction based on the number of axes

  • 2 1/2 axes machine (obsolete today): There are two interpolating axes (X and Y). The third axis (Z) is set in by pneumatic stroke. Different depths of work can be realised e.g. by a revolver with different stops.
  • 3-axes machine: There are 3 controlled linear axes X, Y and Z. The tool can reach any point within the working area, but can not change its working angle and therefore it can not change the angle to the workpiece.
  • 3 1/2-axes and 4-axes machine: In addition to the linear axes there is a rotational axis. This can be a positioning axis (3 1/2 axis) or an interpolating axis (4 axes). Usually at woodworking machines the 4th axis is a C-Axis to do horizontal machining with adapter aggregates at different angles.
  • 5-axis machine: To reach every point within the working area with a tool in any angle to the workpiece there are 5 axes necessary. In practice there are usually restrictions, e.g. often the machine table prevents the tool from processing at the underside of the workpiece.

Images

Erste CNC der Holzbearbeitung: CNC-Portalfräse von Shoda
SHODA, 1968
Point-to-Point Bohrmaschine (EUMASPEED)
3-Achs Bearbeitungszentrum
SCM
5-Achs Bearbeitungszentrum
BACCI