This OPC UA ObjectTyperepresents a CNC channel with all its necessary elements. All Objectsof Type CncChannelTypeare listed in the CncChannelListof the CncInterface Object.

Additionally to data that is relevant for a CNC Channel, CncChannelTypeorganizes Objectsof type CncAxisTypeand CncSpindleType. That is to indicate which components are currently administrated by this channel.

Objectsof CncChannelTypemay generate two kinds of events: Events of type CncMessageTypeand of type GeneralModelChangeEventType.

Events of Type CncMessageTypeare used to provide channel specific messages that are not an alarm but an uncritical information, e.g. a user created message out of the CNC part program.

Events of type GeneralModelChangeEventTypeare used to inform about changes in the Information Model. Examples for the need of a model change event:

  • A CNC channel can administrate a different set of components during runtime, meaning that an axis or a spindle can change its channel affiliation during runtime of the CNC system; for instance this may be the case if one spindle is used in combination with different axis groups.
  • Spindles allow different kind of operation modes, for instance a spindle can change its mode of operation from speed to position control and therefore has to be represented once as spindle (CncSpindleType) and once as rotational axis (CncAxisType).

Instances of CncChannelTypeprovide the position of the channel’s tool center point in different coordinate systems. Therefore, the following definitions have to be considered:

Tool carrier zero point: The tool carrier zero point is a reference point on the tool carrier as illustrated in Figure 10.


Figure 10– Tool carrier zero point for milling and turning tools

Tool center point: The tool center point of tools for milling operations is usually the intersection of the tool centerline and the lowest positioned cutting tip (edge). For turning operations the tool center point is an imaginary tool point of the cutting insert, because most tools have a cutting edge with a built-in radius. The tool center point of point-to-point tools, such as drills, is the extreme tip of the tool, as measured along the Z axis. Figure 11and Figure 12illustrate some common tool center points.


Figure 11– Example tool center points for milling tools


Figure 12– Example tool center points for turning tools

Machine tool coordinate systems: This companion standard refers to two coordinate systems (see Figure 13for illustration):

  • Base coordinate system: The base coordinate system (BCS) is a coordinate system defined by the machine tool manufacturer. It has its origin within the machine tool’s zero point M.
  • Workpiece coordinate system: The workpiece coordinate system (WCS) is a user defined coordinate system and allows considering the clamping position and orientation of a workpiece. It has its origin within the workpiece zero point W.


Figure 13– Machine tool’s coordinate systems and reference points

The coordinate systems are built based on the right-hand-rule, illustrated in Figure 14.


Figure 14– Coordinate systems: positive directions and orientations (DIN66217)

Figure 15shows an overview for the CncChannelType.It is formally defined in Table 12.


Figure 15– CncChannelType