The idea of a tightening system is to represent an easy-to-understand entity that can manage tightening processes autonomously, forming single point of contact for external systems.

Usually, a tightening process drives threaded fastener in a counterpart. This is most likely done by the rotation of one of the fastener parts. Hence, there is a tension force applied to the materials, which are meant to get fastened. Hereby the process will be controlled and supervised by the controller. There are numerous parameters and boundaries which may be set and measurements which are taken during the tightening process.

The measurement data and results are of eminent importance for the assessment of the process quality. This data should mostly be made available to higher-level systems.

In addition to the core process of tightening, other supporting functionalities exist in a tightening system. These are, for example, the advance of the bit, socket, or the supply of the fastening elements.

The tightening system should be able to represent the many different forms of systems that exists today and allow freedom to be extended as more become available.

The core asset in a tightening system is a controller which handles also the OPC UA communication. The definition of the controller is kept wide by design. It could be a server, a PLC, an embedded processor, etc.

Some of the tightening systems that exists today are:

• A physical controller, managing a cable handheld tool and a set of battery handheld tools.
• A physical controller managing several wireless tools.
• A wireless tool containing a controller.
• A controller managing several fixtured spindles.
• A controller managing a spindle, a screw feeder and a screw feeder controller mounted on a robot (The robot is not part of the tightening system).
• A clutch tool reporting OK/NOT_OK.
• A computer system storing and providing historical results or visualizing the information.

The set of models defined in OPC 40451-1 UA CS for Tightening Systems 1.00 are moved to the common base specification OPC 40450-1 for Joining Systems.