Probing systems for CNC machine tools - RENISHAW - #5

An optical transmission system uses infra-red technology for communicating between the probe and the CNC controller and comprises the following:

The probe receives machine control signals and transmits probe status signals. There are two active modes, "stand by" and "operating". In "stand by" mode the probe is a receiver waiting for a signal to switch to operating mode. In operating mode it transmits probe information to the OMM receiver. Probe battery status information is also transmitted in the same manner.

The OMM is the reception/transmission communication partner for the probe module. It is hard-wired to a machine interface unit.

The interface converts probe signal information into a form which is compatible with the machine controller. In addition it has visual and /or audible indicators for probe status, system power, battery status and error diagnostics.

The functions of the OMM and MI12 have been combined into a single module, the optical machine interface (OMI) offering functionality specifically optimized for the needs of smaller machine tools.

A Renishaw probe must be able to communicate with the control system (CNC) of the machine on which it is fitted. Signals must pass from the probe to the machine's controller to register contact of the probe's stylus with the component or tool. Similarly, signals must pass from the machines' controller to probe to control the functioning of the probe.

The passage of these signals is handled by a transmission system. The choice of transmission system depends on the type of probe and the type of machine tool to which it is fitted.

Inspection probes for machining centres are typically located in a tool carousel and are interchanged like conventional tools. On lathes, the probe is typically a semi­permanent feature of a rotating turret. In both case, signalling between probe and CNC generally has to be remote.

For tool setting applications, typically the probe is mounted in a fixed location, thereby allowing direct communication between probe and CNC.

Renishaw probes use four main types of transmission systems:

■ Optical

■ Radio

■ Inductive

- Direct or 'hard-wired'

The following sections show typical examples of each of these systems:

■ Inspection systems on small to large sized machining centres and lathes.